/* SPDX-License-Identifier: GPL-2.0+ */ /* * Read-Copy Update mechanism for mutual exclusion (tree-based version) * Internal non-public definitions that provide either classic * or preemptible semantics. * * Copyright Red Hat, 2009 * Copyright IBM Corporation, 2009 * * Author: Ingo Molnar <mingo@elte.hu> * Paul E. McKenney <paulmck@linux.ibm.com> */ #include "../locking/rtmutex_common.h" #ifdef CONFIG_RCU_NOCB_CPU static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */ static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */ #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ /* * Check the RCU kernel configuration parameters and print informative * messages about anything out of the ordinary. */ static void __init rcu_bootup_announce_oddness(void) { <------>if (IS_ENABLED(CONFIG_RCU_TRACE)) <------><------>pr_info("\tRCU event tracing is enabled.\n"); <------>if ((IS_ENABLED(CONFIG_64BIT) && RCU_FANOUT != 64) || <------> (!IS_ENABLED(CONFIG_64BIT) && RCU_FANOUT != 32)) <------><------>pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d.\n", <------><------><------>RCU_FANOUT); <------>if (rcu_fanout_exact) <------><------>pr_info("\tHierarchical RCU autobalancing is disabled.\n"); <------>if (IS_ENABLED(CONFIG_RCU_FAST_NO_HZ)) <------><------>pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n"); <------>if (IS_ENABLED(CONFIG_PROVE_RCU)) <------><------>pr_info("\tRCU lockdep checking is enabled.\n"); <------>if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) <------><------>pr_info("\tRCU strict (and thus non-scalable) grace periods enabled.\n"); <------>if (RCU_NUM_LVLS >= 4) <------><------>pr_info("\tFour(or more)-level hierarchy is enabled.\n"); <------>if (RCU_FANOUT_LEAF != 16) <------><------>pr_info("\tBuild-time adjustment of leaf fanout to %d.\n", <------><------><------>RCU_FANOUT_LEAF); <------>if (rcu_fanout_leaf != RCU_FANOUT_LEAF) <------><------>pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", <------><------><------>rcu_fanout_leaf); <------>if (nr_cpu_ids != NR_CPUS) <------><------>pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%u.\n", NR_CPUS, nr_cpu_ids); #ifdef CONFIG_RCU_BOOST <------>pr_info("\tRCU priority boosting: priority %d delay %d ms.\n", <------><------>kthread_prio, CONFIG_RCU_BOOST_DELAY); #endif <------>if (blimit != DEFAULT_RCU_BLIMIT) <------><------>pr_info("\tBoot-time adjustment of callback invocation limit to %ld.\n", blimit); <------>if (qhimark != DEFAULT_RCU_QHIMARK) <------><------>pr_info("\tBoot-time adjustment of callback high-water mark to %ld.\n", qhimark); <------>if (qlowmark != DEFAULT_RCU_QLOMARK) <------><------>pr_info("\tBoot-time adjustment of callback low-water mark to %ld.\n", qlowmark); <------>if (qovld != DEFAULT_RCU_QOVLD) <------><------>pr_info("\tBoot-time adjustment of callback overload level to %ld.\n", qovld); <------>if (jiffies_till_first_fqs != ULONG_MAX) <------><------>pr_info("\tBoot-time adjustment of first FQS scan delay to %ld jiffies.\n", jiffies_till_first_fqs); <------>if (jiffies_till_next_fqs != ULONG_MAX) <------><------>pr_info("\tBoot-time adjustment of subsequent FQS scan delay to %ld jiffies.\n", jiffies_till_next_fqs); <------>if (jiffies_till_sched_qs != ULONG_MAX) <------><------>pr_info("\tBoot-time adjustment of scheduler-enlistment delay to %ld jiffies.\n", jiffies_till_sched_qs); <------>if (rcu_kick_kthreads) <------><------>pr_info("\tKick kthreads if too-long grace period.\n"); <------>if (IS_ENABLED(CONFIG_DEBUG_OBJECTS_RCU_HEAD)) <------><------>pr_info("\tRCU callback double-/use-after-free debug enabled.\n"); <------>if (gp_preinit_delay) <------><------>pr_info("\tRCU debug GP pre-init slowdown %d jiffies.\n", gp_preinit_delay); <------>if (gp_init_delay) <------><------>pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_init_delay); <------>if (gp_cleanup_delay) <------><------>pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_cleanup_delay); <------>if (!use_softirq) <------><------>pr_info("\tRCU_SOFTIRQ processing moved to rcuc kthreads.\n"); <------>if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG)) <------><------>pr_info("\tRCU debug extended QS entry/exit.\n"); <------>rcupdate_announce_bootup_oddness(); } #ifdef CONFIG_PREEMPT_RCU static void rcu_report_exp_rnp(struct rcu_node *rnp, bool wake); static void rcu_read_unlock_special(struct task_struct *t); /* * Tell them what RCU they are running. */ static void __init rcu_bootup_announce(void) { <------>pr_info("Preemptible hierarchical RCU implementation.\n"); <------>rcu_bootup_announce_oddness(); } /* Flags for rcu_preempt_ctxt_queue() decision table. */ #define RCU_GP_TASKS 0x8 #define RCU_EXP_TASKS 0x4 #define RCU_GP_BLKD 0x2 #define RCU_EXP_BLKD 0x1 /* * Queues a task preempted within an RCU-preempt read-side critical * section into the appropriate location within the ->blkd_tasks list, * depending on the states of any ongoing normal and expedited grace * periods. The ->gp_tasks pointer indicates which element the normal * grace period is waiting on (NULL if none), and the ->exp_tasks pointer * indicates which element the expedited grace period is waiting on (again, * NULL if none). If a grace period is waiting on a given element in the * ->blkd_tasks list, it also waits on all subsequent elements. Thus, * adding a task to the tail of the list blocks any grace period that is * already waiting on one of the elements. In contrast, adding a task * to the head of the list won't block any grace period that is already * waiting on one of the elements. * * This queuing is imprecise, and can sometimes make an ongoing grace * period wait for a task that is not strictly speaking blocking it. * Given the choice, we needlessly block a normal grace period rather than * blocking an expedited grace period. * * Note that an endless sequence of expedited grace periods still cannot * indefinitely postpone a normal grace period. Eventually, all of the * fixed number of preempted tasks blocking the normal grace period that are * not also blocking the expedited grace period will resume and complete * their RCU read-side critical sections. At that point, the ->gp_tasks * pointer will equal the ->exp_tasks pointer, at which point the end of * the corresponding expedited grace period will also be the end of the * normal grace period. */ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp) <------>__releases(rnp->lock) /* But leaves rrupts disabled. */ { <------>int blkd_state = (rnp->gp_tasks ? RCU_GP_TASKS : 0) + <------><------><------> (rnp->exp_tasks ? RCU_EXP_TASKS : 0) + <------><------><------> (rnp->qsmask & rdp->grpmask ? RCU_GP_BLKD : 0) + <------><------><------> (rnp->expmask & rdp->grpmask ? RCU_EXP_BLKD : 0); <------>struct task_struct *t = current; <------>raw_lockdep_assert_held_rcu_node(rnp); <------>WARN_ON_ONCE(rdp->mynode != rnp); <------>WARN_ON_ONCE(!rcu_is_leaf_node(rnp)); <------>/* RCU better not be waiting on newly onlined CPUs! */ <------>WARN_ON_ONCE(rnp->qsmaskinitnext & ~rnp->qsmaskinit & rnp->qsmask & <------><------> rdp->grpmask); <------>/* <------> * Decide where to queue the newly blocked task. In theory, <------> * this could be an if-statement. In practice, when I tried <------> * that, it was quite messy. <------> */ <------>switch (blkd_state) { <------>case 0: <------>case RCU_EXP_TASKS: <------>case RCU_EXP_TASKS + RCU_GP_BLKD: <------>case RCU_GP_TASKS: <------>case RCU_GP_TASKS + RCU_EXP_TASKS: <------><------>/* <------><------> * Blocking neither GP, or first task blocking the normal <------><------> * GP but not blocking the already-waiting expedited GP. <------><------> * Queue at the head of the list to avoid unnecessarily <------><------> * blocking the already-waiting GPs. <------><------> */ <------><------>list_add(&t->rcu_node_entry, &rnp->blkd_tasks); <------><------>break; <------>case RCU_EXP_BLKD: <------>case RCU_GP_BLKD: <------>case RCU_GP_BLKD + RCU_EXP_BLKD: <------>case RCU_GP_TASKS + RCU_EXP_BLKD: <------>case RCU_GP_TASKS + RCU_GP_BLKD + RCU_EXP_BLKD: <------>case RCU_GP_TASKS + RCU_EXP_TASKS + RCU_GP_BLKD + RCU_EXP_BLKD: <------><------>/* <------><------> * First task arriving that blocks either GP, or first task <------><------> * arriving that blocks the expedited GP (with the normal <------><------> * GP already waiting), or a task arriving that blocks <------><------> * both GPs with both GPs already waiting. Queue at the <------><------> * tail of the list to avoid any GP waiting on any of the <------><------> * already queued tasks that are not blocking it. <------><------> */ <------><------>list_add_tail(&t->rcu_node_entry, &rnp->blkd_tasks); <------><------>break; <------>case RCU_EXP_TASKS + RCU_EXP_BLKD: <------>case RCU_EXP_TASKS + RCU_GP_BLKD + RCU_EXP_BLKD: <------>case RCU_GP_TASKS + RCU_EXP_TASKS + RCU_EXP_BLKD: <------><------>/* <------><------> * Second or subsequent task blocking the expedited GP. <------><------> * The task either does not block the normal GP, or is the <------><------> * first task blocking the normal GP. Queue just after <------><------> * the first task blocking the expedited GP. <------><------> */ <------><------>list_add(&t->rcu_node_entry, rnp->exp_tasks); <------><------>break; <------>case RCU_GP_TASKS + RCU_GP_BLKD: <------>case RCU_GP_TASKS + RCU_EXP_TASKS + RCU_GP_BLKD: <------><------>/* <------><------> * Second or subsequent task blocking the normal GP. <------><------> * The task does not block the expedited GP. Queue just <------><------> * after the first task blocking the normal GP. <------><------> */ <------><------>list_add(&t->rcu_node_entry, rnp->gp_tasks); <------><------>break; <------>default: <------><------>/* Yet another exercise in excessive paranoia. */ <------><------>WARN_ON_ONCE(1); <------><------>break; <------>} <------>/* <------> * We have now queued the task. If it was the first one to <------> * block either grace period, update the ->gp_tasks and/or <------> * ->exp_tasks pointers, respectively, to reference the newly <------> * blocked tasks. <------> */ <------>if (!rnp->gp_tasks && (blkd_state & RCU_GP_BLKD)) { <------><------>WRITE_ONCE(rnp->gp_tasks, &t->rcu_node_entry); <------><------>WARN_ON_ONCE(rnp->completedqs == rnp->gp_seq); <------>} <------>if (!rnp->exp_tasks && (blkd_state & RCU_EXP_BLKD)) <------><------>WRITE_ONCE(rnp->exp_tasks, &t->rcu_node_entry); <------>WARN_ON_ONCE(!(blkd_state & RCU_GP_BLKD) != <------><------> !(rnp->qsmask & rdp->grpmask)); <------>WARN_ON_ONCE(!(blkd_state & RCU_EXP_BLKD) != <------><------> !(rnp->expmask & rdp->grpmask)); <------>raw_spin_unlock_rcu_node(rnp); /* interrupts remain disabled. */ <------>/* <------> * Report the quiescent state for the expedited GP. This expedited <------> * GP should not be able to end until we report, so there should be <------> * no need to check for a subsequent expedited GP. (Though we are <------> * still in a quiescent state in any case.) <------> */ <------>if (blkd_state & RCU_EXP_BLKD && rdp->exp_deferred_qs) <------><------>rcu_report_exp_rdp(rdp); <------>else <------><------>WARN_ON_ONCE(rdp->exp_deferred_qs); } /* * Record a preemptible-RCU quiescent state for the specified CPU. * Note that this does not necessarily mean that the task currently running * on the CPU is in a quiescent state: Instead, it means that the current * grace period need not wait on any RCU read-side critical section that * starts later on this CPU. It also means that if the current task is * in an RCU read-side critical section, it has already added itself to * some leaf rcu_node structure's ->blkd_tasks list. In addition to the * current task, there might be any number of other tasks blocked while * in an RCU read-side critical section. * * Callers to this function must disable preemption. */ static void rcu_qs(void) { <------>RCU_LOCKDEP_WARN(preemptible(), "rcu_qs() invoked with preemption enabled!!!\n"); <------>if (__this_cpu_read(rcu_data.cpu_no_qs.s)) { <------><------>trace_rcu_grace_period(TPS("rcu_preempt"), <------><------><------><------> __this_cpu_read(rcu_data.gp_seq), <------><------><------><------> TPS("cpuqs")); <------><------>__this_cpu_write(rcu_data.cpu_no_qs.b.norm, false); <------><------>barrier(); /* Coordinate with rcu_flavor_sched_clock_irq(). */ <------><------>WRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, false); <------>} } /* * We have entered the scheduler, and the current task might soon be * context-switched away from. If this task is in an RCU read-side * critical section, we will no longer be able to rely on the CPU to * record that fact, so we enqueue the task on the blkd_tasks list. * The task will dequeue itself when it exits the outermost enclosing * RCU read-side critical section. Therefore, the current grace period * cannot be permitted to complete until the blkd_tasks list entries * predating the current grace period drain, in other words, until * rnp->gp_tasks becomes NULL. * * Caller must disable interrupts. */ void rcu_note_context_switch(bool preempt) { <------>struct task_struct *t = current; <------>struct rcu_data *rdp = this_cpu_ptr(&rcu_data); <------>struct rcu_node *rnp; <------>trace_rcu_utilization(TPS("Start context switch")); <------>lockdep_assert_irqs_disabled(); <------>WARN_ON_ONCE(!preempt && rcu_preempt_depth() > 0); <------>if (rcu_preempt_depth() > 0 && <------> !t->rcu_read_unlock_special.b.blocked) { <------><------>/* Possibly blocking in an RCU read-side critical section. */ <------><------>rnp = rdp->mynode; <------><------>raw_spin_lock_rcu_node(rnp); <------><------>t->rcu_read_unlock_special.b.blocked = true; <------><------>t->rcu_blocked_node = rnp; <------><------>/* <------><------> * Verify the CPU's sanity, trace the preemption, and <------><------> * then queue the task as required based on the states <------><------> * of any ongoing and expedited grace periods. <------><------> */ <------><------>WARN_ON_ONCE((rdp->grpmask & rcu_rnp_online_cpus(rnp)) == 0); <------><------>WARN_ON_ONCE(!list_empty(&t->rcu_node_entry)); <------><------>trace_rcu_preempt_task(rcu_state.name, <------><------><------><------> t->pid, <------><------><------><------> (rnp->qsmask & rdp->grpmask) <------><------><------><------> ? rnp->gp_seq <------><------><------><------> : rcu_seq_snap(&rnp->gp_seq)); <------><------>rcu_preempt_ctxt_queue(rnp, rdp); <------>} else { <------><------>rcu_preempt_deferred_qs(t); <------>} <------>/* <------> * Either we were not in an RCU read-side critical section to <------> * begin with, or we have now recorded that critical section <------> * globally. Either way, we can now note a quiescent state <------> * for this CPU. Again, if we were in an RCU read-side critical <------> * section, and if that critical section was blocking the current <------> * grace period, then the fact that the task has been enqueued <------> * means that we continue to block the current grace period. <------> */ <------>rcu_qs(); <------>if (rdp->exp_deferred_qs) <------><------>rcu_report_exp_rdp(rdp); <------>rcu_tasks_qs(current, preempt); <------>trace_rcu_utilization(TPS("End context switch")); } EXPORT_SYMBOL_GPL(rcu_note_context_switch); /* * Check for preempted RCU readers blocking the current grace period * for the specified rcu_node structure. If the caller needs a reliable * answer, it must hold the rcu_node's ->lock. */ static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) { <------>return READ_ONCE(rnp->gp_tasks) != NULL; } /* limit value for ->rcu_read_lock_nesting. */ #define RCU_NEST_PMAX (INT_MAX / 2) static void rcu_preempt_read_enter(void) { <------>current->rcu_read_lock_nesting++; } static int rcu_preempt_read_exit(void) { <------>return --current->rcu_read_lock_nesting; } static void rcu_preempt_depth_set(int val) { <------>current->rcu_read_lock_nesting = val; } /* * Preemptible RCU implementation for rcu_read_lock(). * Just increment ->rcu_read_lock_nesting, shared state will be updated * if we block. */ void __rcu_read_lock(void) { <------>rcu_preempt_read_enter(); <------>if (IS_ENABLED(CONFIG_PROVE_LOCKING)) <------><------>WARN_ON_ONCE(rcu_preempt_depth() > RCU_NEST_PMAX); <------>if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) && rcu_state.gp_kthread) <------><------>WRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, true); <------>barrier(); /* critical section after entry code. */ } EXPORT_SYMBOL_GPL(__rcu_read_lock); /* * Preemptible RCU implementation for rcu_read_unlock(). * Decrement ->rcu_read_lock_nesting. If the result is zero (outermost * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then * invoke rcu_read_unlock_special() to clean up after a context switch * in an RCU read-side critical section and other special cases. */ void __rcu_read_unlock(void) { <------>struct task_struct *t = current; <------>if (rcu_preempt_read_exit() == 0) { <------><------>barrier(); /* critical section before exit code. */ <------><------>if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s))) <------><------><------>rcu_read_unlock_special(t); <------>} <------>if (IS_ENABLED(CONFIG_PROVE_LOCKING)) { <------><------>int rrln = rcu_preempt_depth(); <------><------>WARN_ON_ONCE(rrln < 0 || rrln > RCU_NEST_PMAX); <------>} } EXPORT_SYMBOL_GPL(__rcu_read_unlock); /* * Advance a ->blkd_tasks-list pointer to the next entry, instead * returning NULL if at the end of the list. */ static struct list_head *rcu_next_node_entry(struct task_struct *t, <------><------><------><------><------> struct rcu_node *rnp) { <------>struct list_head *np; <------>np = t->rcu_node_entry.next; <------>if (np == &rnp->blkd_tasks) <------><------>np = NULL; <------>return np; } /* * Return true if the specified rcu_node structure has tasks that were * preempted within an RCU read-side critical section. */ static bool rcu_preempt_has_tasks(struct rcu_node *rnp) { <------>return !list_empty(&rnp->blkd_tasks); } /* * Report deferred quiescent states. The deferral time can * be quite short, for example, in the case of the call from * rcu_read_unlock_special(). */ static void rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags) { <------>bool empty_exp; <------>bool empty_norm; <------>bool empty_exp_now; <------>struct list_head *np; <------>bool drop_boost_mutex = false; <------>struct rcu_data *rdp; <------>struct rcu_node *rnp; <------>union rcu_special special; <------>/* <------> * If RCU core is waiting for this CPU to exit its critical section, <------> * report the fact that it has exited. Because irqs are disabled, <------> * t->rcu_read_unlock_special cannot change. <------> */ <------>special = t->rcu_read_unlock_special; <------>rdp = this_cpu_ptr(&rcu_data); <------>if (!special.s && !rdp->exp_deferred_qs) { <------><------>local_irq_restore(flags); <------><------>return; <------>} <------>t->rcu_read_unlock_special.s = 0; <------>if (special.b.need_qs) { <------><------>if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) { <------><------><------>rcu_report_qs_rdp(rdp); <------><------><------>udelay(rcu_unlock_delay); <------><------>} else { <------><------><------>rcu_qs(); <------><------>} <------>} <------>/* <------> * Respond to a request by an expedited grace period for a <------> * quiescent state from this CPU. Note that requests from <------> * tasks are handled when removing the task from the <------> * blocked-tasks list below. <------> */ <------>if (rdp->exp_deferred_qs) <------><------>rcu_report_exp_rdp(rdp); <------>/* Clean up if blocked during RCU read-side critical section. */ <------>if (special.b.blocked) { <------><------>/* <------><------> * Remove this task from the list it blocked on. The task <------><------> * now remains queued on the rcu_node corresponding to the <------><------> * CPU it first blocked on, so there is no longer any need <------><------> * to loop. Retain a WARN_ON_ONCE() out of sheer paranoia. <------><------> */ <------><------>rnp = t->rcu_blocked_node; <------><------>raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ <------><------>WARN_ON_ONCE(rnp != t->rcu_blocked_node); <------><------>WARN_ON_ONCE(!rcu_is_leaf_node(rnp)); <------><------>empty_norm = !rcu_preempt_blocked_readers_cgp(rnp); <------><------>WARN_ON_ONCE(rnp->completedqs == rnp->gp_seq && <------><------><------> (!empty_norm || rnp->qsmask)); <------><------>empty_exp = sync_rcu_exp_done(rnp); <------><------>smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */ <------><------>np = rcu_next_node_entry(t, rnp); <------><------>list_del_init(&t->rcu_node_entry); <------><------>t->rcu_blocked_node = NULL; <------><------>trace_rcu_unlock_preempted_task(TPS("rcu_preempt"), <------><------><------><------><------><------>rnp->gp_seq, t->pid); <------><------>if (&t->rcu_node_entry == rnp->gp_tasks) <------><------><------>WRITE_ONCE(rnp->gp_tasks, np); <------><------>if (&t->rcu_node_entry == rnp->exp_tasks) <------><------><------>WRITE_ONCE(rnp->exp_tasks, np); <------><------>if (IS_ENABLED(CONFIG_RCU_BOOST)) { <------><------><------>/* Snapshot ->boost_mtx ownership w/rnp->lock held. */ <------><------><------>drop_boost_mutex = rt_mutex_owner(&rnp->boost_mtx) == t; <------><------><------>if (&t->rcu_node_entry == rnp->boost_tasks) <------><------><------><------>WRITE_ONCE(rnp->boost_tasks, np); <------><------>} <------><------>/* <------><------> * If this was the last task on the current list, and if <------><------> * we aren't waiting on any CPUs, report the quiescent state. <------><------> * Note that rcu_report_unblock_qs_rnp() releases rnp->lock, <------><------> * so we must take a snapshot of the expedited state. <------><------> */ <------><------>empty_exp_now = sync_rcu_exp_done(rnp); <------><------>if (!empty_norm && !rcu_preempt_blocked_readers_cgp(rnp)) { <------><------><------>trace_rcu_quiescent_state_report(TPS("preempt_rcu"), <------><------><------><------><------><------><------> rnp->gp_seq, <------><------><------><------><------><------><------> 0, rnp->qsmask, <------><------><------><------><------><------><------> rnp->level, <------><------><------><------><------><------><------> rnp->grplo, <------><------><------><------><------><------><------> rnp->grphi, <------><------><------><------><------><------><------> !!rnp->gp_tasks); <------><------><------>rcu_report_unblock_qs_rnp(rnp, flags); <------><------>} else { <------><------><------>raw_spin_unlock_irqrestore_rcu_node(rnp, flags); <------><------>} <------><------>/* <------><------> * If this was the last task on the expedited lists, <------><------> * then we need to report up the rcu_node hierarchy. <------><------> */ <------><------>if (!empty_exp && empty_exp_now) <------><------><------>rcu_report_exp_rnp(rnp, true); <------><------>/* Unboost if we were boosted. */ <------><------>if (IS_ENABLED(CONFIG_RCU_BOOST) && drop_boost_mutex) <------><------><------>rt_mutex_futex_unlock(&rnp->boost_mtx); <------>} else { <------><------>local_irq_restore(flags); <------>} } /* * Is a deferred quiescent-state pending, and are we also not in * an RCU read-side critical section? It is the caller's responsibility * to ensure it is otherwise safe to report any deferred quiescent * states. The reason for this is that it is safe to report a * quiescent state during context switch even though preemption * is disabled. This function cannot be expected to understand these * nuances, so the caller must handle them. */ static bool rcu_preempt_need_deferred_qs(struct task_struct *t) { <------>return (__this_cpu_read(rcu_data.exp_deferred_qs) || <------><------>READ_ONCE(t->rcu_read_unlock_special.s)) && <------> rcu_preempt_depth() == 0; } /* * Report a deferred quiescent state if needed and safe to do so. * As with rcu_preempt_need_deferred_qs(), "safe" involves only * not being in an RCU read-side critical section. The caller must * evaluate safety in terms of interrupt, softirq, and preemption * disabling. */ static void rcu_preempt_deferred_qs(struct task_struct *t) { <------>unsigned long flags; <------>if (!rcu_preempt_need_deferred_qs(t)) <------><------>return; <------>local_irq_save(flags); <------>rcu_preempt_deferred_qs_irqrestore(t, flags); } /* * Minimal handler to give the scheduler a chance to re-evaluate. */ static void rcu_preempt_deferred_qs_handler(struct irq_work *iwp) { <------>struct rcu_data *rdp; <------>rdp = container_of(iwp, struct rcu_data, defer_qs_iw); <------>rdp->defer_qs_iw_pending = false; } /* * Handle special cases during rcu_read_unlock(), such as needing to * notify RCU core processing or task having blocked during the RCU * read-side critical section. */ static void rcu_read_unlock_special(struct task_struct *t) { <------>unsigned long flags; <------>bool preempt_bh_were_disabled = <------><------><------>!!(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK)); <------>bool irqs_were_disabled; <------>/* NMI handlers cannot block and cannot safely manipulate state. */ <------>if (in_nmi()) <------><------>return; <------>local_irq_save(flags); <------>irqs_were_disabled = irqs_disabled_flags(flags); <------>if (preempt_bh_were_disabled || irqs_were_disabled) { <------><------>bool exp; <------><------>struct rcu_data *rdp = this_cpu_ptr(&rcu_data); <------><------>struct rcu_node *rnp = rdp->mynode; <------><------>exp = (t->rcu_blocked_node && <------><------> READ_ONCE(t->rcu_blocked_node->exp_tasks)) || <------><------> (rdp->grpmask & READ_ONCE(rnp->expmask)); <------><------>// Need to defer quiescent state until everything is enabled. <------><------>if (use_softirq && (in_irq() || (exp && !irqs_were_disabled))) { <------><------><------>// Using softirq, safe to awaken, and either the <------><------><------>// wakeup is free or there is an expedited GP. <------><------><------>raise_softirq_irqoff(RCU_SOFTIRQ); <------><------>} else { <------><------><------>// Enabling BH or preempt does reschedule, so... <------><------><------>// Also if no expediting, slow is OK. <------><------><------>// Plus nohz_full CPUs eventually get tick enabled. <------><------><------>set_tsk_need_resched(current); <------><------><------>set_preempt_need_resched(); <------><------><------>if (IS_ENABLED(CONFIG_IRQ_WORK) && irqs_were_disabled && <------><------><------> !rdp->defer_qs_iw_pending && exp && cpu_online(rdp->cpu)) { <------><------><------><------>// Get scheduler to re-evaluate and call hooks. <------><------><------><------>// If !IRQ_WORK, FQS scan will eventually IPI. <------><------><------><------>init_irq_work(&rdp->defer_qs_iw, <------><------><------><------><------> rcu_preempt_deferred_qs_handler); <------><------><------><------>rdp->defer_qs_iw_pending = true; <------><------><------><------>irq_work_queue_on(&rdp->defer_qs_iw, rdp->cpu); <------><------><------>} <------><------>} <------><------>local_irq_restore(flags); <------><------>return; <------>} <------>rcu_preempt_deferred_qs_irqrestore(t, flags); } /* * Check that the list of blocked tasks for the newly completed grace * period is in fact empty. It is a serious bug to complete a grace * period that still has RCU readers blocked! This function must be * invoked -before- updating this rnp's ->gp_seq. * * Also, if there are blocked tasks on the list, they automatically * block the newly created grace period, so set up ->gp_tasks accordingly. */ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) { <------>struct task_struct *t; <------>RCU_LOCKDEP_WARN(preemptible(), "rcu_preempt_check_blocked_tasks() invoked with preemption enabled!!!\n"); <------>raw_lockdep_assert_held_rcu_node(rnp); <------>if (WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp))) <------><------>dump_blkd_tasks(rnp, 10); <------>if (rcu_preempt_has_tasks(rnp) && <------> (rnp->qsmaskinit || rnp->wait_blkd_tasks)) { <------><------>WRITE_ONCE(rnp->gp_tasks, rnp->blkd_tasks.next); <------><------>t = container_of(rnp->gp_tasks, struct task_struct, <------><------><------><------> rcu_node_entry); <------><------>trace_rcu_unlock_preempted_task(TPS("rcu_preempt-GPS"), <------><------><------><------><------><------>rnp->gp_seq, t->pid); <------>} <------>WARN_ON_ONCE(rnp->qsmask); } /* * Check for a quiescent state from the current CPU, including voluntary * context switches for Tasks RCU. When a task blocks, the task is * recorded in the corresponding CPU's rcu_node structure, which is checked * elsewhere, hence this function need only check for quiescent states * related to the current CPU, not to those related to tasks. */ static void rcu_flavor_sched_clock_irq(int user) { <------>struct task_struct *t = current; <------>lockdep_assert_irqs_disabled(); <------>if (user || rcu_is_cpu_rrupt_from_idle()) { <------><------>rcu_note_voluntary_context_switch(current); <------>} <------>if (rcu_preempt_depth() > 0 || <------> (preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK))) { <------><------>/* No QS, force context switch if deferred. */ <------><------>if (rcu_preempt_need_deferred_qs(t)) { <------><------><------>set_tsk_need_resched(t); <------><------><------>set_preempt_need_resched(); <------><------>} <------>} else if (rcu_preempt_need_deferred_qs(t)) { <------><------>rcu_preempt_deferred_qs(t); /* Report deferred QS. */ <------><------>return; <------>} else if (!WARN_ON_ONCE(rcu_preempt_depth())) { <------><------>rcu_qs(); /* Report immediate QS. */ <------><------>return; <------>} <------>/* If GP is oldish, ask for help from rcu_read_unlock_special(). */ <------>if (rcu_preempt_depth() > 0 && <------> __this_cpu_read(rcu_data.core_needs_qs) && <------> __this_cpu_read(rcu_data.cpu_no_qs.b.norm) && <------> !t->rcu_read_unlock_special.b.need_qs && <------> time_after(jiffies, rcu_state.gp_start + HZ)) <------><------>t->rcu_read_unlock_special.b.need_qs = true; } /* * Check for a task exiting while in a preemptible-RCU read-side * critical section, clean up if so. No need to issue warnings, as * debug_check_no_locks_held() already does this if lockdep is enabled. * Besides, if this function does anything other than just immediately * return, there was a bug of some sort. Spewing warnings from this * function is like as not to simply obscure important prior warnings. */ void exit_rcu(void) { <------>struct task_struct *t = current; <------>if (unlikely(!list_empty(¤t->rcu_node_entry))) { <------><------>rcu_preempt_depth_set(1); <------><------>barrier(); <------><------>WRITE_ONCE(t->rcu_read_unlock_special.b.blocked, true); <------>} else if (unlikely(rcu_preempt_depth())) { <------><------>rcu_preempt_depth_set(1); <------>} else { <------><------>return; <------>} <------>__rcu_read_unlock(); <------>rcu_preempt_deferred_qs(current); } /* * Dump the blocked-tasks state, but limit the list dump to the * specified number of elements. */ static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck) { <------>int cpu; <------>int i; <------>struct list_head *lhp; <------>bool onl; <------>struct rcu_data *rdp; <------>struct rcu_node *rnp1; <------>raw_lockdep_assert_held_rcu_node(rnp); <------>pr_info("%s: grp: %d-%d level: %d ->gp_seq %ld ->completedqs %ld\n", <------><------>__func__, rnp->grplo, rnp->grphi, rnp->level, <------><------>(long)READ_ONCE(rnp->gp_seq), (long)rnp->completedqs); <------>for (rnp1 = rnp; rnp1; rnp1 = rnp1->parent) <------><------>pr_info("%s: %d:%d ->qsmask %#lx ->qsmaskinit %#lx ->qsmaskinitnext %#lx\n", <------><------><------>__func__, rnp1->grplo, rnp1->grphi, rnp1->qsmask, rnp1->qsmaskinit, rnp1->qsmaskinitnext); <------>pr_info("%s: ->gp_tasks %p ->boost_tasks %p ->exp_tasks %p\n", <------><------>__func__, READ_ONCE(rnp->gp_tasks), data_race(rnp->boost_tasks), <------><------>READ_ONCE(rnp->exp_tasks)); <------>pr_info("%s: ->blkd_tasks", __func__); <------>i = 0; <------>list_for_each(lhp, &rnp->blkd_tasks) { <------><------>pr_cont(" %p", lhp); <------><------>if (++i >= ncheck) <------><------><------>break; <------>} <------>pr_cont("\n"); <------>for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) { <------><------>rdp = per_cpu_ptr(&rcu_data, cpu); <------><------>onl = !!(rdp->grpmask & rcu_rnp_online_cpus(rnp)); <------><------>pr_info("\t%d: %c online: %ld(%d) offline: %ld(%d)\n", <------><------><------>cpu, ".o"[onl], <------><------><------>(long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags, <------><------><------>(long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags); <------>} } #else /* #ifdef CONFIG_PREEMPT_RCU */ /* * If strict grace periods are enabled, and if the calling * __rcu_read_unlock() marks the beginning of a quiescent state, immediately * report that quiescent state and, if requested, spin for a bit. */ void rcu_read_unlock_strict(void) { <------>struct rcu_data *rdp; <------>if (!IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) || <------> irqs_disabled() || preempt_count() || !rcu_state.gp_kthread) <------><------>return; <------>rdp = this_cpu_ptr(&rcu_data); <------>rcu_report_qs_rdp(rdp); <------>udelay(rcu_unlock_delay); } EXPORT_SYMBOL_GPL(rcu_read_unlock_strict); /* * Tell them what RCU they are running. */ static void __init rcu_bootup_announce(void) { <------>pr_info("Hierarchical RCU implementation.\n"); <------>rcu_bootup_announce_oddness(); } /* * Note a quiescent state for PREEMPTION=n. Because we do not need to know * how many quiescent states passed, just if there was at least one since * the start of the grace period, this just sets a flag. The caller must * have disabled preemption. */ static void rcu_qs(void) { <------>RCU_LOCKDEP_WARN(preemptible(), "rcu_qs() invoked with preemption enabled!!!"); <------>if (!__this_cpu_read(rcu_data.cpu_no_qs.s)) <------><------>return; <------>trace_rcu_grace_period(TPS("rcu_sched"), <------><------><------> __this_cpu_read(rcu_data.gp_seq), TPS("cpuqs")); <------>__this_cpu_write(rcu_data.cpu_no_qs.b.norm, false); <------>if (!__this_cpu_read(rcu_data.cpu_no_qs.b.exp)) <------><------>return; <------>__this_cpu_write(rcu_data.cpu_no_qs.b.exp, false); <------>rcu_report_exp_rdp(this_cpu_ptr(&rcu_data)); } /* * Register an urgently needed quiescent state. If there is an * emergency, invoke rcu_momentary_dyntick_idle() to do a heavy-weight * dyntick-idle quiescent state visible to other CPUs, which will in * some cases serve for expedited as well as normal grace periods. * Either way, register a lightweight quiescent state. */ void rcu_all_qs(void) { <------>unsigned long flags; <------>if (!raw_cpu_read(rcu_data.rcu_urgent_qs)) <------><------>return; <------>preempt_disable(); <------>/* Load rcu_urgent_qs before other flags. */ <------>if (!smp_load_acquire(this_cpu_ptr(&rcu_data.rcu_urgent_qs))) { <------><------>preempt_enable(); <------><------>return; <------>} <------>this_cpu_write(rcu_data.rcu_urgent_qs, false); <------>if (unlikely(raw_cpu_read(rcu_data.rcu_need_heavy_qs))) { <------><------>local_irq_save(flags); <------><------>rcu_momentary_dyntick_idle(); <------><------>local_irq_restore(flags); <------>} <------>rcu_qs(); <------>preempt_enable(); } EXPORT_SYMBOL_GPL(rcu_all_qs); /* * Note a PREEMPTION=n context switch. The caller must have disabled interrupts. */ void rcu_note_context_switch(bool preempt) { <------>trace_rcu_utilization(TPS("Start context switch")); <------>rcu_qs(); <------>/* Load rcu_urgent_qs before other flags. */ <------>if (!smp_load_acquire(this_cpu_ptr(&rcu_data.rcu_urgent_qs))) <------><------>goto out; <------>this_cpu_write(rcu_data.rcu_urgent_qs, false); <------>if (unlikely(raw_cpu_read(rcu_data.rcu_need_heavy_qs))) <------><------>rcu_momentary_dyntick_idle(); <------>rcu_tasks_qs(current, preempt); out: <------>trace_rcu_utilization(TPS("End context switch")); } EXPORT_SYMBOL_GPL(rcu_note_context_switch); /* * Because preemptible RCU does not exist, there are never any preempted * RCU readers. */ static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) { <------>return 0; } /* * Because there is no preemptible RCU, there can be no readers blocked. */ static bool rcu_preempt_has_tasks(struct rcu_node *rnp) { <------>return false; } /* * Because there is no preemptible RCU, there can be no deferred quiescent * states. */ static bool rcu_preempt_need_deferred_qs(struct task_struct *t) { <------>return false; } static void rcu_preempt_deferred_qs(struct task_struct *t) { } /* * Because there is no preemptible RCU, there can be no readers blocked, * so there is no need to check for blocked tasks. So check only for * bogus qsmask values. */ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) { <------>WARN_ON_ONCE(rnp->qsmask); } /* * Check to see if this CPU is in a non-context-switch quiescent state, * namely user mode and idle loop. */ static void rcu_flavor_sched_clock_irq(int user) { <------>if (user || rcu_is_cpu_rrupt_from_idle()) { <------><------>/* <------><------> * Get here if this CPU took its interrupt from user <------><------> * mode or from the idle loop, and if this is not a <------><------> * nested interrupt. In this case, the CPU is in <------><------> * a quiescent state, so note it. <------><------> * <------><------> * No memory barrier is required here because rcu_qs() <------><------> * references only CPU-local variables that other CPUs <------><------> * neither access nor modify, at least not while the <------><------> * corresponding CPU is online. <------><------> */ <------><------>rcu_qs(); <------>} } /* * Because preemptible RCU does not exist, tasks cannot possibly exit * while in preemptible RCU read-side critical sections. */ void exit_rcu(void) { } /* * Dump the guaranteed-empty blocked-tasks state. Trust but verify. */ static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck) { <------>WARN_ON_ONCE(!list_empty(&rnp->blkd_tasks)); } #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ /* * If boosting, set rcuc kthreads to realtime priority. */ static void rcu_cpu_kthread_setup(unsigned int cpu) { #ifdef CONFIG_RCU_BOOST <------>struct sched_param sp; <------>sp.sched_priority = kthread_prio; <------>sched_setscheduler_nocheck(current, SCHED_FIFO, &sp); #endif /* #ifdef CONFIG_RCU_BOOST */ } #ifdef CONFIG_RCU_BOOST /* * Carry out RCU priority boosting on the task indicated by ->exp_tasks * or ->boost_tasks, advancing the pointer to the next task in the * ->blkd_tasks list. * * Note that irqs must be enabled: boosting the task can block. * Returns 1 if there are more tasks needing to be boosted. */ static int rcu_boost(struct rcu_node *rnp) { <------>unsigned long flags; <------>struct task_struct *t; <------>struct list_head *tb; <------>if (READ_ONCE(rnp->exp_tasks) == NULL && <------> READ_ONCE(rnp->boost_tasks) == NULL) <------><------>return 0; /* Nothing left to boost. */ <------>raw_spin_lock_irqsave_rcu_node(rnp, flags); <------>/* <------> * Recheck under the lock: all tasks in need of boosting <------> * might exit their RCU read-side critical sections on their own. <------> */ <------>if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) { <------><------>raw_spin_unlock_irqrestore_rcu_node(rnp, flags); <------><------>return 0; <------>} <------>/* <------> * Preferentially boost tasks blocking expedited grace periods. <------> * This cannot starve the normal grace periods because a second <------> * expedited grace period must boost all blocked tasks, including <------> * those blocking the pre-existing normal grace period. <------> */ <------>if (rnp->exp_tasks != NULL) <------><------>tb = rnp->exp_tasks; <------>else <------><------>tb = rnp->boost_tasks; <------>/* <------> * We boost task t by manufacturing an rt_mutex that appears to <------> * be held by task t. We leave a pointer to that rt_mutex where <------> * task t can find it, and task t will release the mutex when it <------> * exits its outermost RCU read-side critical section. Then <------> * simply acquiring this artificial rt_mutex will boost task <------> * t's priority. (Thanks to tglx for suggesting this approach!) <------> * <------> * Note that task t must acquire rnp->lock to remove itself from <------> * the ->blkd_tasks list, which it will do from exit() if from <------> * nowhere else. We therefore are guaranteed that task t will <------> * stay around at least until we drop rnp->lock. Note that <------> * rnp->lock also resolves races between our priority boosting <------> * and task t's exiting its outermost RCU read-side critical <------> * section. <------> */ <------>t = container_of(tb, struct task_struct, rcu_node_entry); <------>rt_mutex_init_proxy_locked(&rnp->boost_mtx, t); <------>raw_spin_unlock_irqrestore_rcu_node(rnp, flags); <------>/* Lock only for side effect: boosts task t's priority. */ <------>rt_mutex_lock(&rnp->boost_mtx); <------>rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */ <------>return READ_ONCE(rnp->exp_tasks) != NULL || <------> READ_ONCE(rnp->boost_tasks) != NULL; } /* * Priority-boosting kthread, one per leaf rcu_node. */ static int rcu_boost_kthread(void *arg) { <------>struct rcu_node *rnp = (struct rcu_node *)arg; <------>int spincnt = 0; <------>int more2boost; <------>trace_rcu_utilization(TPS("Start boost kthread@init")); <------>for (;;) { <------><------>WRITE_ONCE(rnp->boost_kthread_status, RCU_KTHREAD_WAITING); <------><------>trace_rcu_utilization(TPS("End boost kthread@rcu_wait")); <------><------>rcu_wait(READ_ONCE(rnp->boost_tasks) || <------><------><------> READ_ONCE(rnp->exp_tasks)); <------><------>trace_rcu_utilization(TPS("Start boost kthread@rcu_wait")); <------><------>WRITE_ONCE(rnp->boost_kthread_status, RCU_KTHREAD_RUNNING); <------><------>more2boost = rcu_boost(rnp); <------><------>if (more2boost) <------><------><------>spincnt++; <------><------>else <------><------><------>spincnt = 0; <------><------>if (spincnt > 10) { <------><------><------>WRITE_ONCE(rnp->boost_kthread_status, RCU_KTHREAD_YIELDING); <------><------><------>trace_rcu_utilization(TPS("End boost kthread@rcu_yield")); <------><------><------>schedule_timeout_idle(2); <------><------><------>trace_rcu_utilization(TPS("Start boost kthread@rcu_yield")); <------><------><------>spincnt = 0; <------><------>} <------>} <------>/* NOTREACHED */ <------>trace_rcu_utilization(TPS("End boost kthread@notreached")); <------>return 0; } /* * Check to see if it is time to start boosting RCU readers that are * blocking the current grace period, and, if so, tell the per-rcu_node * kthread to start boosting them. If there is an expedited grace * period in progress, it is always time to boost. * * The caller must hold rnp->lock, which this function releases. * The ->boost_kthread_task is immortal, so we don't need to worry * about it going away. */ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) <------>__releases(rnp->lock) { <------>raw_lockdep_assert_held_rcu_node(rnp); <------>if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) { <------><------>raw_spin_unlock_irqrestore_rcu_node(rnp, flags); <------><------>return; <------>} <------>if (rnp->exp_tasks != NULL || <------> (rnp->gp_tasks != NULL && <------> rnp->boost_tasks == NULL && <------> rnp->qsmask == 0 && <------> (!time_after(rnp->boost_time, jiffies) || rcu_state.cbovld))) { <------><------>if (rnp->exp_tasks == NULL) <------><------><------>WRITE_ONCE(rnp->boost_tasks, rnp->gp_tasks); <------><------>raw_spin_unlock_irqrestore_rcu_node(rnp, flags); <------><------>rcu_wake_cond(rnp->boost_kthread_task, <------><------><------> READ_ONCE(rnp->boost_kthread_status)); <------>} else { <------><------>raw_spin_unlock_irqrestore_rcu_node(rnp, flags); <------>} } /* * Is the current CPU running the RCU-callbacks kthread? * Caller must have preemption disabled. */ static bool rcu_is_callbacks_kthread(void) { <------>return __this_cpu_read(rcu_data.rcu_cpu_kthread_task) == current; } #define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000) /* * Do priority-boost accounting for the start of a new grace period. */ static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) { <------>rnp->boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES; } /* * Create an RCU-boost kthread for the specified node if one does not * already exist. We only create this kthread for preemptible RCU. * Returns zero if all is well, a negated errno otherwise. */ static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp) { <------>int rnp_index = rnp - rcu_get_root(); <------>unsigned long flags; <------>struct sched_param sp; <------>struct task_struct *t; <------>if (!IS_ENABLED(CONFIG_PREEMPT_RCU)) <------><------>return; <------>if (!rcu_scheduler_fully_active || rcu_rnp_online_cpus(rnp) == 0) <------><------>return; <------>rcu_state.boost = 1; <------>if (rnp->boost_kthread_task != NULL) <------><------>return; <------>t = kthread_create(rcu_boost_kthread, (void *)rnp, <------><------><------> "rcub/%d", rnp_index); <------>if (WARN_ON_ONCE(IS_ERR(t))) <------><------>return; <------>raw_spin_lock_irqsave_rcu_node(rnp, flags); <------>rnp->boost_kthread_task = t; <------>raw_spin_unlock_irqrestore_rcu_node(rnp, flags); <------>sp.sched_priority = kthread_prio; <------>sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); <------>wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */ } /* * Set the per-rcu_node kthread's affinity to cover all CPUs that are * served by the rcu_node in question. The CPU hotplug lock is still * held, so the value of rnp->qsmaskinit will be stable. * * We don't include outgoingcpu in the affinity set, use -1 if there is * no outgoing CPU. If there are no CPUs left in the affinity set, * this function allows the kthread to execute on any CPU. */ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) { <------>struct task_struct *t = rnp->boost_kthread_task; <------>unsigned long mask = rcu_rnp_online_cpus(rnp); <------>cpumask_var_t cm; <------>int cpu; <------>if (!t) <------><------>return; <------>if (!zalloc_cpumask_var(&cm, GFP_KERNEL)) <------><------>return; <------>for_each_leaf_node_possible_cpu(rnp, cpu) <------><------>if ((mask & leaf_node_cpu_bit(rnp, cpu)) && <------><------> cpu != outgoingcpu) <------><------><------>cpumask_set_cpu(cpu, cm); <------>if (cpumask_weight(cm) == 0) <------><------>cpumask_setall(cm); <------>set_cpus_allowed_ptr(t, cm); <------>free_cpumask_var(cm); } /* * Spawn boost kthreads -- called as soon as the scheduler is running. */ static void __init rcu_spawn_boost_kthreads(void) { <------>struct rcu_node *rnp; <------>rcu_for_each_leaf_node(rnp) <------><------>rcu_spawn_one_boost_kthread(rnp); } static void rcu_prepare_kthreads(int cpu) { <------>struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); <------>struct rcu_node *rnp = rdp->mynode; <------>/* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */ <------>if (rcu_scheduler_fully_active) <------><------>rcu_spawn_one_boost_kthread(rnp); } #else /* #ifdef CONFIG_RCU_BOOST */ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) <------>__releases(rnp->lock) { <------>raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } static bool rcu_is_callbacks_kthread(void) { <------>return false; } static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) { } static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) { } static void __init rcu_spawn_boost_kthreads(void) { } static void rcu_prepare_kthreads(int cpu) { } #endif /* #else #ifdef CONFIG_RCU_BOOST */ #if !defined(CONFIG_RCU_FAST_NO_HZ) /* * Check to see if any future non-offloaded RCU-related work will need * to be done by the current CPU, even if none need be done immediately, * returning 1 if so. This function is part of the RCU implementation; * it is -not- an exported member of the RCU API. * * Because we not have RCU_FAST_NO_HZ, just check whether or not this * CPU has RCU callbacks queued. */ int rcu_needs_cpu(u64 basemono, u64 *nextevt) { <------>*nextevt = KTIME_MAX; <------>return !rcu_segcblist_empty(&this_cpu_ptr(&rcu_data)->cblist) && <------> !rcu_segcblist_is_offloaded(&this_cpu_ptr(&rcu_data)->cblist); } /* * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up * after it. */ static void rcu_cleanup_after_idle(void) { } /* * Do the idle-entry grace-period work, which, because CONFIG_RCU_FAST_NO_HZ=n, * is nothing. */ static void rcu_prepare_for_idle(void) { } #else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */ /* * This code is invoked when a CPU goes idle, at which point we want * to have the CPU do everything required for RCU so that it can enter * the energy-efficient dyntick-idle mode. * * The following preprocessor symbol controls this: * * RCU_IDLE_GP_DELAY gives the number of jiffies that a CPU is permitted * to sleep in dyntick-idle mode with RCU callbacks pending. This * is sized to be roughly one RCU grace period. Those energy-efficiency * benchmarkers who might otherwise be tempted to set this to a large * number, be warned: Setting RCU_IDLE_GP_DELAY too high can hang your * system. And if you are -that- concerned about energy efficiency, * just power the system down and be done with it! * * The value below works well in practice. If future workloads require * adjustment, they can be converted into kernel config parameters, though * making the state machine smarter might be a better option. */ #define RCU_IDLE_GP_DELAY 4 /* Roughly one grace period. */ static int rcu_idle_gp_delay = RCU_IDLE_GP_DELAY; module_param(rcu_idle_gp_delay, int, 0644); /* * Try to advance callbacks on the current CPU, but only if it has been * awhile since the last time we did so. Afterwards, if there are any * callbacks ready for immediate invocation, return true. */ static bool __maybe_unused rcu_try_advance_all_cbs(void) { <------>bool cbs_ready = false; <------>struct rcu_data *rdp = this_cpu_ptr(&rcu_data); <------>struct rcu_node *rnp; <------>/* Exit early if we advanced recently. */ <------>if (jiffies == rdp->last_advance_all) <------><------>return false; <------>rdp->last_advance_all = jiffies; <------>rnp = rdp->mynode; <------>/* <------> * Don't bother checking unless a grace period has <------> * completed since we last checked and there are <------> * callbacks not yet ready to invoke. <------> */ <------>if ((rcu_seq_completed_gp(rdp->gp_seq, <------><------><------><------> rcu_seq_current(&rnp->gp_seq)) || <------> unlikely(READ_ONCE(rdp->gpwrap))) && <------> rcu_segcblist_pend_cbs(&rdp->cblist)) <------><------>note_gp_changes(rdp); <------>if (rcu_segcblist_ready_cbs(&rdp->cblist)) <------><------>cbs_ready = true; <------>return cbs_ready; } /* * Allow the CPU to enter dyntick-idle mode unless it has callbacks ready * to invoke. If the CPU has callbacks, try to advance them. Tell the * caller about what to set the timeout. * * The caller must have disabled interrupts. */ int rcu_needs_cpu(u64 basemono, u64 *nextevt) { <------>struct rcu_data *rdp = this_cpu_ptr(&rcu_data); <------>unsigned long dj; <------>lockdep_assert_irqs_disabled(); <------>/* If no non-offloaded callbacks, RCU doesn't need the CPU. */ <------>if (rcu_segcblist_empty(&rdp->cblist) || <------> rcu_segcblist_is_offloaded(&this_cpu_ptr(&rcu_data)->cblist)) { <------><------>*nextevt = KTIME_MAX; <------><------>return 0; <------>} <------>/* Attempt to advance callbacks. */ <------>if (rcu_try_advance_all_cbs()) { <------><------>/* Some ready to invoke, so initiate later invocation. */ <------><------>invoke_rcu_core(); <------><------>return 1; <------>} <------>rdp->last_accelerate = jiffies; <------>/* Request timer and round. */ <------>dj = round_up(rcu_idle_gp_delay + jiffies, rcu_idle_gp_delay) - jiffies; <------>*nextevt = basemono + dj * TICK_NSEC; <------>return 0; } /* * Prepare a CPU for idle from an RCU perspective. The first major task is to * sense whether nohz mode has been enabled or disabled via sysfs. The second * major task is to accelerate (that is, assign grace-period numbers to) any * recently arrived callbacks. * * The caller must have disabled interrupts. */ static void rcu_prepare_for_idle(void) { <------>bool needwake; <------>struct rcu_data *rdp = this_cpu_ptr(&rcu_data); <------>struct rcu_node *rnp; <------>int tne; <------>lockdep_assert_irqs_disabled(); <------>if (rcu_segcblist_is_offloaded(&rdp->cblist)) <------><------>return; <------>/* Handle nohz enablement switches conservatively. */ <------>tne = READ_ONCE(tick_nohz_active); <------>if (tne != rdp->tick_nohz_enabled_snap) { <------><------>if (!rcu_segcblist_empty(&rdp->cblist)) <------><------><------>invoke_rcu_core(); /* force nohz to see update. */ <------><------>rdp->tick_nohz_enabled_snap = tne; <------><------>return; <------>} <------>if (!tne) <------><------>return; <------>/* <------> * If we have not yet accelerated this jiffy, accelerate all <------> * callbacks on this CPU. <------> */ <------>if (rdp->last_accelerate == jiffies) <------><------>return; <------>rdp->last_accelerate = jiffies; <------>if (rcu_segcblist_pend_cbs(&rdp->cblist)) { <------><------>rnp = rdp->mynode; <------><------>raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ <------><------>needwake = rcu_accelerate_cbs(rnp, rdp); <------><------>raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ <------><------>if (needwake) <------><------><------>rcu_gp_kthread_wake(); <------>} } /* * Clean up for exit from idle. Attempt to advance callbacks based on * any grace periods that elapsed while the CPU was idle, and if any * callbacks are now ready to invoke, initiate invocation. */ static void rcu_cleanup_after_idle(void) { <------>struct rcu_data *rdp = this_cpu_ptr(&rcu_data); <------>lockdep_assert_irqs_disabled(); <------>if (rcu_segcblist_is_offloaded(&rdp->cblist)) <------><------>return; <------>if (rcu_try_advance_all_cbs()) <------><------>invoke_rcu_core(); } #endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */ #ifdef CONFIG_RCU_NOCB_CPU /* * Offload callback processing from the boot-time-specified set of CPUs * specified by rcu_nocb_mask. For the CPUs in the set, there are kthreads * created that pull the callbacks from the corresponding CPU, wait for * a grace period to elapse, and invoke the callbacks. These kthreads * are organized into GP kthreads, which manage incoming callbacks, wait for * grace periods, and awaken CB kthreads, and the CB kthreads, which only * invoke callbacks. Each GP kthread invokes its own CBs. The no-CBs CPUs * do a wake_up() on their GP kthread when they insert a callback into any * empty list, unless the rcu_nocb_poll boot parameter has been specified, * in which case each kthread actively polls its CPU. (Which isn't so great * for energy efficiency, but which does reduce RCU's overhead on that CPU.) * * This is intended to be used in conjunction with Frederic Weisbecker's * adaptive-idle work, which would seriously reduce OS jitter on CPUs * running CPU-bound user-mode computations. * * Offloading of callbacks can also be used as an energy-efficiency * measure because CPUs with no RCU callbacks queued are more aggressive * about entering dyntick-idle mode. */ /* * Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters. * The string after the "rcu_nocbs=" is either "all" for all CPUs, or a * comma-separated list of CPUs and/or CPU ranges. If an invalid list is * given, a warning is emitted and all CPUs are offloaded. */ static int __init rcu_nocb_setup(char *str) { <------>alloc_bootmem_cpumask_var(&rcu_nocb_mask); <------>if (!strcasecmp(str, "all")) <------><------>cpumask_setall(rcu_nocb_mask); <------>else <------><------>if (cpulist_parse(str, rcu_nocb_mask)) { <------><------><------>pr_warn("rcu_nocbs= bad CPU range, all CPUs set\n"); <------><------><------>cpumask_setall(rcu_nocb_mask); <------><------>} <------>return 1; } __setup("rcu_nocbs=", rcu_nocb_setup); static int __init parse_rcu_nocb_poll(char *arg) { <------>rcu_nocb_poll = true; <------>return 0; } early_param("rcu_nocb_poll", parse_rcu_nocb_poll); /* * Don't bother bypassing ->cblist if the call_rcu() rate is low. * After all, the main point of bypassing is to avoid lock contention * on ->nocb_lock, which only can happen at high call_rcu() rates. */ int nocb_nobypass_lim_per_jiffy = 16 * 1000 / HZ; module_param(nocb_nobypass_lim_per_jiffy, int, 0); /* * Acquire the specified rcu_data structure's ->nocb_bypass_lock. If the * lock isn't immediately available, increment ->nocb_lock_contended to * flag the contention. */ static void rcu_nocb_bypass_lock(struct rcu_data *rdp) <------>__acquires(&rdp->nocb_bypass_lock) { <------>lockdep_assert_irqs_disabled(); <------>if (raw_spin_trylock(&rdp->nocb_bypass_lock)) <------><------>return; <------>atomic_inc(&rdp->nocb_lock_contended); <------>WARN_ON_ONCE(smp_processor_id() != rdp->cpu); <------>smp_mb__after_atomic(); /* atomic_inc() before lock. */ <------>raw_spin_lock(&rdp->nocb_bypass_lock); <------>smp_mb__before_atomic(); /* atomic_dec() after lock. */ <------>atomic_dec(&rdp->nocb_lock_contended); } /* * Spinwait until the specified rcu_data structure's ->nocb_lock is * not contended. Please note that this is extremely special-purpose, * relying on the fact that at most two kthreads and one CPU contend for * this lock, and also that the two kthreads are guaranteed to have frequent * grace-period-duration time intervals between successive acquisitions * of the lock. This allows us to use an extremely simple throttling * mechanism, and further to apply it only to the CPU doing floods of * call_rcu() invocations. Don't try this at home! */ static void rcu_nocb_wait_contended(struct rcu_data *rdp) { <------>WARN_ON_ONCE(smp_processor_id() != rdp->cpu); <------>while (WARN_ON_ONCE(atomic_read(&rdp->nocb_lock_contended))) <------><------>cpu_relax(); } /* * Conditionally acquire the specified rcu_data structure's * ->nocb_bypass_lock. */ static bool rcu_nocb_bypass_trylock(struct rcu_data *rdp) { <------>lockdep_assert_irqs_disabled(); <------>return raw_spin_trylock(&rdp->nocb_bypass_lock); } /* * Release the specified rcu_data structure's ->nocb_bypass_lock. */ static void rcu_nocb_bypass_unlock(struct rcu_data *rdp) <------>__releases(&rdp->nocb_bypass_lock) { <------>lockdep_assert_irqs_disabled(); <------>raw_spin_unlock(&rdp->nocb_bypass_lock); } /* * Acquire the specified rcu_data structure's ->nocb_lock, but only * if it corresponds to a no-CBs CPU. */ static void rcu_nocb_lock(struct rcu_data *rdp) { <------>lockdep_assert_irqs_disabled(); <------>if (!rcu_segcblist_is_offloaded(&rdp->cblist)) <------><------>return; <------>raw_spin_lock(&rdp->nocb_lock); } /* * Release the specified rcu_data structure's ->nocb_lock, but only * if it corresponds to a no-CBs CPU. */ static void rcu_nocb_unlock(struct rcu_data *rdp) { <------>if (rcu_segcblist_is_offloaded(&rdp->cblist)) { <------><------>lockdep_assert_irqs_disabled(); <------><------>raw_spin_unlock(&rdp->nocb_lock); <------>} } /* * Release the specified rcu_data structure's ->nocb_lock and restore * interrupts, but only if it corresponds to a no-CBs CPU. */ static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp, <------><------><------><------> unsigned long flags) { <------>if (rcu_segcblist_is_offloaded(&rdp->cblist)) { <------><------>lockdep_assert_irqs_disabled(); <------><------>raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); <------>} else { <------><------>local_irq_restore(flags); <------>} } /* Lockdep check that ->cblist may be safely accessed. */ static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp) { <------>lockdep_assert_irqs_disabled(); <------>if (rcu_segcblist_is_offloaded(&rdp->cblist)) <------><------>lockdep_assert_held(&rdp->nocb_lock); } /* * Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended * grace period. */ static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq) { <------>swake_up_all(sq); } static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp) { <------>return &rnp->nocb_gp_wq[rcu_seq_ctr(rnp->gp_seq) & 0x1]; } static void rcu_init_one_nocb(struct rcu_node *rnp) { <------>init_swait_queue_head(&rnp->nocb_gp_wq[0]); <------>init_swait_queue_head(&rnp->nocb_gp_wq[1]); } /* Is the specified CPU a no-CBs CPU? */ bool rcu_is_nocb_cpu(int cpu) { <------>if (cpumask_available(rcu_nocb_mask)) <------><------>return cpumask_test_cpu(cpu, rcu_nocb_mask); <------>return false; } /* * Kick the GP kthread for this NOCB group. Caller holds ->nocb_lock * and this function releases it. */ static void wake_nocb_gp(struct rcu_data *rdp, bool force, <------><------><------> unsigned long flags) <------>__releases(rdp->nocb_lock) { <------>bool needwake = false; <------>struct rcu_data *rdp_gp = rdp->nocb_gp_rdp; <------>lockdep_assert_held(&rdp->nocb_lock); <------>if (!READ_ONCE(rdp_gp->nocb_gp_kthread)) { <------><------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, <------><------><------><------> TPS("AlreadyAwake")); <------><------>rcu_nocb_unlock_irqrestore(rdp, flags); <------><------>return; <------>} <------>if (READ_ONCE(rdp->nocb_defer_wakeup) > RCU_NOCB_WAKE_NOT) { <------><------>WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT); <------><------>del_timer(&rdp->nocb_timer); <------>} <------>rcu_nocb_unlock_irqrestore(rdp, flags); <------>raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags); <------>if (force || READ_ONCE(rdp_gp->nocb_gp_sleep)) { <------><------>WRITE_ONCE(rdp_gp->nocb_gp_sleep, false); <------><------>needwake = true; <------><------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("DoWake")); <------>} <------>raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags); <------>if (needwake) <------><------>wake_up_process(rdp_gp->nocb_gp_kthread); } /* * Arrange to wake the GP kthread for this NOCB group at some future * time when it is safe to do so. */ static void wake_nocb_gp_defer(struct rcu_data *rdp, int waketype, <------><------><------> const char *reason) { <------>if (rdp->nocb_defer_wakeup == RCU_NOCB_WAKE_NOT) <------><------>mod_timer(&rdp->nocb_timer, jiffies + 1); <------>if (rdp->nocb_defer_wakeup < waketype) <------><------>WRITE_ONCE(rdp->nocb_defer_wakeup, waketype); <------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, reason); } /* * Flush the ->nocb_bypass queue into ->cblist, enqueuing rhp if non-NULL. * However, if there is a callback to be enqueued and if ->nocb_bypass * proves to be initially empty, just return false because the no-CB GP * kthread may need to be awakened in this case. * * Note that this function always returns true if rhp is NULL. */ static bool rcu_nocb_do_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp, <------><------><------><------> unsigned long j) { <------>struct rcu_cblist rcl; <------>WARN_ON_ONCE(!rcu_segcblist_is_offloaded(&rdp->cblist)); <------>rcu_lockdep_assert_cblist_protected(rdp); <------>lockdep_assert_held(&rdp->nocb_bypass_lock); <------>if (rhp && !rcu_cblist_n_cbs(&rdp->nocb_bypass)) { <------><------>raw_spin_unlock(&rdp->nocb_bypass_lock); <------><------>return false; <------>} <------>/* Note: ->cblist.len already accounts for ->nocb_bypass contents. */ <------>if (rhp) <------><------>rcu_segcblist_inc_len(&rdp->cblist); /* Must precede enqueue. */ <------>rcu_cblist_flush_enqueue(&rcl, &rdp->nocb_bypass, rhp); <------>rcu_segcblist_insert_pend_cbs(&rdp->cblist, &rcl); <------>WRITE_ONCE(rdp->nocb_bypass_first, j); <------>rcu_nocb_bypass_unlock(rdp); <------>return true; } /* * Flush the ->nocb_bypass queue into ->cblist, enqueuing rhp if non-NULL. * However, if there is a callback to be enqueued and if ->nocb_bypass * proves to be initially empty, just return false because the no-CB GP * kthread may need to be awakened in this case. * * Note that this function always returns true if rhp is NULL. */ static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp, <------><------><------><------> unsigned long j) { <------>if (!rcu_segcblist_is_offloaded(&rdp->cblist)) <------><------>return true; <------>rcu_lockdep_assert_cblist_protected(rdp); <------>rcu_nocb_bypass_lock(rdp); <------>return rcu_nocb_do_flush_bypass(rdp, rhp, j); } /* * If the ->nocb_bypass_lock is immediately available, flush the * ->nocb_bypass queue into ->cblist. */ static void rcu_nocb_try_flush_bypass(struct rcu_data *rdp, unsigned long j) { <------>rcu_lockdep_assert_cblist_protected(rdp); <------>if (!rcu_segcblist_is_offloaded(&rdp->cblist) || <------> !rcu_nocb_bypass_trylock(rdp)) <------><------>return; <------>WARN_ON_ONCE(!rcu_nocb_do_flush_bypass(rdp, NULL, j)); } /* * See whether it is appropriate to use the ->nocb_bypass list in order * to control contention on ->nocb_lock. A limited number of direct * enqueues are permitted into ->cblist per jiffy. If ->nocb_bypass * is non-empty, further callbacks must be placed into ->nocb_bypass, * otherwise rcu_barrier() breaks. Use rcu_nocb_flush_bypass() to switch * back to direct use of ->cblist. However, ->nocb_bypass should not be * used if ->cblist is empty, because otherwise callbacks can be stranded * on ->nocb_bypass because we cannot count on the current CPU ever again * invoking call_rcu(). The general rule is that if ->nocb_bypass is * non-empty, the corresponding no-CBs grace-period kthread must not be * in an indefinite sleep state. * * Finally, it is not permitted to use the bypass during early boot, * as doing so would confuse the auto-initialization code. Besides * which, there is no point in worrying about lock contention while * there is only one CPU in operation. */ static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp, <------><------><------><------>bool *was_alldone, unsigned long flags) { <------>unsigned long c; <------>unsigned long cur_gp_seq; <------>unsigned long j = jiffies; <------>long ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass); <------>if (!rcu_segcblist_is_offloaded(&rdp->cblist)) { <------><------>*was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist); <------><------>return false; /* Not offloaded, no bypassing. */ <------>} <------>lockdep_assert_irqs_disabled(); <------>// Don't use ->nocb_bypass during early boot. <------>if (rcu_scheduler_active != RCU_SCHEDULER_RUNNING) { <------><------>rcu_nocb_lock(rdp); <------><------>WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass)); <------><------>*was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist); <------><------>return false; <------>} <------>// If we have advanced to a new jiffy, reset counts to allow <------>// moving back from ->nocb_bypass to ->cblist. <------>if (j == rdp->nocb_nobypass_last) { <------><------>c = rdp->nocb_nobypass_count + 1; <------>} else { <------><------>WRITE_ONCE(rdp->nocb_nobypass_last, j); <------><------>c = rdp->nocb_nobypass_count - nocb_nobypass_lim_per_jiffy; <------><------>if (ULONG_CMP_LT(rdp->nocb_nobypass_count, <------><------><------><------> nocb_nobypass_lim_per_jiffy)) <------><------><------>c = 0; <------><------>else if (c > nocb_nobypass_lim_per_jiffy) <------><------><------>c = nocb_nobypass_lim_per_jiffy; <------>} <------>WRITE_ONCE(rdp->nocb_nobypass_count, c); <------>// If there hasn't yet been all that many ->cblist enqueues <------>// this jiffy, tell the caller to enqueue onto ->cblist. But flush <------>// ->nocb_bypass first. <------>if (rdp->nocb_nobypass_count < nocb_nobypass_lim_per_jiffy) { <------><------>rcu_nocb_lock(rdp); <------><------>*was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist); <------><------>if (*was_alldone) <------><------><------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, <------><------><------><------><------> TPS("FirstQ")); <------><------>WARN_ON_ONCE(!rcu_nocb_flush_bypass(rdp, NULL, j)); <------><------>WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass)); <------><------>return false; // Caller must enqueue the callback. <------>} <------>// If ->nocb_bypass has been used too long or is too full, <------>// flush ->nocb_bypass to ->cblist. <------>if ((ncbs && j != READ_ONCE(rdp->nocb_bypass_first)) || <------> ncbs >= qhimark) { <------><------>rcu_nocb_lock(rdp); <------><------>if (!rcu_nocb_flush_bypass(rdp, rhp, j)) { <------><------><------>*was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist); <------><------><------>if (*was_alldone) <------><------><------><------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, <------><------><------><------><------><------> TPS("FirstQ")); <------><------><------>WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass)); <------><------><------>return false; // Caller must enqueue the callback. <------><------>} <------><------>if (j != rdp->nocb_gp_adv_time && <------><------> rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq) && <------><------> rcu_seq_done(&rdp->mynode->gp_seq, cur_gp_seq)) { <------><------><------>rcu_advance_cbs_nowake(rdp->mynode, rdp); <------><------><------>rdp->nocb_gp_adv_time = j; <------><------>} <------><------>rcu_nocb_unlock_irqrestore(rdp, flags); <------><------>return true; // Callback already enqueued. <------>} <------>// We need to use the bypass. <------>rcu_nocb_wait_contended(rdp); <------>rcu_nocb_bypass_lock(rdp); <------>ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass); <------>rcu_segcblist_inc_len(&rdp->cblist); /* Must precede enqueue. */ <------>rcu_cblist_enqueue(&rdp->nocb_bypass, rhp); <------>if (!ncbs) { <------><------>WRITE_ONCE(rdp->nocb_bypass_first, j); <------><------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("FirstBQ")); <------>} <------>rcu_nocb_bypass_unlock(rdp); <------>smp_mb(); /* Order enqueue before wake. */ <------>if (ncbs) { <------><------>local_irq_restore(flags); <------>} else { <------><------>// No-CBs GP kthread might be indefinitely asleep, if so, wake. <------><------>rcu_nocb_lock(rdp); // Rare during call_rcu() flood. <------><------>if (!rcu_segcblist_pend_cbs(&rdp->cblist)) { <------><------><------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, <------><------><------><------><------> TPS("FirstBQwake")); <------><------><------>__call_rcu_nocb_wake(rdp, true, flags); <------><------>} else { <------><------><------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, <------><------><------><------><------> TPS("FirstBQnoWake")); <------><------><------>rcu_nocb_unlock_irqrestore(rdp, flags); <------><------>} <------>} <------>return true; // Callback already enqueued. } /* * Awaken the no-CBs grace-period kthead if needed, either due to it * legitimately being asleep or due to overload conditions. * * If warranted, also wake up the kthread servicing this CPUs queues. */ static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_alldone, <------><------><------><------> unsigned long flags) <------><------><------><------> __releases(rdp->nocb_lock) { <------>unsigned long cur_gp_seq; <------>unsigned long j; <------>long len; <------>struct task_struct *t; <------>// If we are being polled or there is no kthread, just leave. <------>t = READ_ONCE(rdp->nocb_gp_kthread); <------>if (rcu_nocb_poll || !t) { <------><------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, <------><------><------><------> TPS("WakeNotPoll")); <------><------>rcu_nocb_unlock_irqrestore(rdp, flags); <------><------>return; <------>} <------>// Need to actually to a wakeup. <------>len = rcu_segcblist_n_cbs(&rdp->cblist); <------>if (was_alldone) { <------><------>rdp->qlen_last_fqs_check = len; <------><------>if (!irqs_disabled_flags(flags)) { <------><------><------>/* ... if queue was empty ... */ <------><------><------>wake_nocb_gp(rdp, false, flags); <------><------><------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, <------><------><------><------><------> TPS("WakeEmpty")); <------><------>} else { <------><------><------>wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE, <------><------><------><------><------> TPS("WakeEmptyIsDeferred")); <------><------><------>rcu_nocb_unlock_irqrestore(rdp, flags); <------><------>} <------>} else if (len > rdp->qlen_last_fqs_check + qhimark) { <------><------>/* ... or if many callbacks queued. */ <------><------>rdp->qlen_last_fqs_check = len; <------><------>j = jiffies; <------><------>if (j != rdp->nocb_gp_adv_time && <------><------> rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq) && <------><------> rcu_seq_done(&rdp->mynode->gp_seq, cur_gp_seq)) { <------><------><------>rcu_advance_cbs_nowake(rdp->mynode, rdp); <------><------><------>rdp->nocb_gp_adv_time = j; <------><------>} <------><------>smp_mb(); /* Enqueue before timer_pending(). */ <------><------>if ((rdp->nocb_cb_sleep || <------><------> !rcu_segcblist_ready_cbs(&rdp->cblist)) && <------><------> !timer_pending(&rdp->nocb_bypass_timer)) <------><------><------>wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE_FORCE, <------><------><------><------><------> TPS("WakeOvfIsDeferred")); <------><------>rcu_nocb_unlock_irqrestore(rdp, flags); <------>} else { <------><------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WakeNot")); <------><------>rcu_nocb_unlock_irqrestore(rdp, flags); <------>} <------>return; } /* Wake up the no-CBs GP kthread to flush ->nocb_bypass. */ static void do_nocb_bypass_wakeup_timer(struct timer_list *t) { <------>unsigned long flags; <------>struct rcu_data *rdp = from_timer(rdp, t, nocb_bypass_timer); <------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("Timer")); <------>rcu_nocb_lock_irqsave(rdp, flags); <------>smp_mb__after_spinlock(); /* Timer expire before wakeup. */ <------>__call_rcu_nocb_wake(rdp, true, flags); } /* * No-CBs GP kthreads come here to wait for additional callbacks to show up * or for grace periods to end. */ static void nocb_gp_wait(struct rcu_data *my_rdp) { <------>bool bypass = false; <------>long bypass_ncbs; <------>int __maybe_unused cpu = my_rdp->cpu; <------>unsigned long cur_gp_seq; <------>unsigned long flags; <------>bool gotcbs = false; <------>unsigned long j = jiffies; <------>bool needwait_gp = false; // This prevents actual uninitialized use. <------>bool needwake; <------>bool needwake_gp; <------>struct rcu_data *rdp; <------>struct rcu_node *rnp; <------>unsigned long wait_gp_seq = 0; // Suppress "use uninitialized" warning. <------>bool wasempty = false; <------>/* <------> * Each pass through the following loop checks for CBs and for the <------> * nearest grace period (if any) to wait for next. The CB kthreads <------> * and the global grace-period kthread are awakened if needed. <------> */ <------>WARN_ON_ONCE(my_rdp->nocb_gp_rdp != my_rdp); <------>for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_cb_rdp) { <------><------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("Check")); <------><------>rcu_nocb_lock_irqsave(rdp, flags); <------><------>bypass_ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass); <------><------>if (bypass_ncbs && <------><------> (time_after(j, READ_ONCE(rdp->nocb_bypass_first) + 1) || <------><------> bypass_ncbs > 2 * qhimark)) { <------><------><------>// Bypass full or old, so flush it. <------><------><------>(void)rcu_nocb_try_flush_bypass(rdp, j); <------><------><------>bypass_ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass); <------><------>} else if (!bypass_ncbs && rcu_segcblist_empty(&rdp->cblist)) { <------><------><------>rcu_nocb_unlock_irqrestore(rdp, flags); <------><------><------>continue; /* No callbacks here, try next. */ <------><------>} <------><------>if (bypass_ncbs) { <------><------><------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, <------><------><------><------><------> TPS("Bypass")); <------><------><------>bypass = true; <------><------>} <------><------>rnp = rdp->mynode; <------><------>if (bypass) { // Avoid race with first bypass CB. <------><------><------>WRITE_ONCE(my_rdp->nocb_defer_wakeup, <------><------><------><------> RCU_NOCB_WAKE_NOT); <------><------><------>del_timer(&my_rdp->nocb_timer); <------><------>} <------><------>// Advance callbacks if helpful and low contention. <------><------>needwake_gp = false; <------><------>if (!rcu_segcblist_restempty(&rdp->cblist, <------><------><------><------><------> RCU_NEXT_READY_TAIL) || <------><------> (rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq) && <------><------> rcu_seq_done(&rnp->gp_seq, cur_gp_seq))) { <------><------><------>raw_spin_lock_rcu_node(rnp); /* irqs disabled. */ <------><------><------>needwake_gp = rcu_advance_cbs(rnp, rdp); <------><------><------>wasempty = rcu_segcblist_restempty(&rdp->cblist, <------><------><------><------><------><------><------> RCU_NEXT_READY_TAIL); <------><------><------>raw_spin_unlock_rcu_node(rnp); /* irqs disabled. */ <------><------>} <------><------>// Need to wait on some grace period? <------><------>WARN_ON_ONCE(wasempty && <------><------><------> !rcu_segcblist_restempty(&rdp->cblist, <------><------><------><------><------><------> RCU_NEXT_READY_TAIL)); <------><------>if (rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq)) { <------><------><------>if (!needwait_gp || <------><------><------> ULONG_CMP_LT(cur_gp_seq, wait_gp_seq)) <------><------><------><------>wait_gp_seq = cur_gp_seq; <------><------><------>needwait_gp = true; <------><------><------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, <------><------><------><------><------> TPS("NeedWaitGP")); <------><------>} <------><------>if (rcu_segcblist_ready_cbs(&rdp->cblist)) { <------><------><------>needwake = rdp->nocb_cb_sleep; <------><------><------>WRITE_ONCE(rdp->nocb_cb_sleep, false); <------><------><------>smp_mb(); /* CB invocation -after- GP end. */ <------><------>} else { <------><------><------>needwake = false; <------><------>} <------><------>rcu_nocb_unlock_irqrestore(rdp, flags); <------><------>if (needwake) { <------><------><------>swake_up_one(&rdp->nocb_cb_wq); <------><------><------>gotcbs = true; <------><------>} <------><------>if (needwake_gp) <------><------><------>rcu_gp_kthread_wake(); <------>} <------>my_rdp->nocb_gp_bypass = bypass; <------>my_rdp->nocb_gp_gp = needwait_gp; <------>my_rdp->nocb_gp_seq = needwait_gp ? wait_gp_seq : 0; <------>if (bypass && !rcu_nocb_poll) { <------><------>// At least one child with non-empty ->nocb_bypass, so set <------><------>// timer in order to avoid stranding its callbacks. <------><------>raw_spin_lock_irqsave(&my_rdp->nocb_gp_lock, flags); <------><------>mod_timer(&my_rdp->nocb_bypass_timer, j + 2); <------><------>raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags); <------>} <------>if (rcu_nocb_poll) { <------><------>/* Polling, so trace if first poll in the series. */ <------><------>if (gotcbs) <------><------><------>trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("Poll")); <------><------>schedule_timeout_idle(1); <------>} else if (!needwait_gp) { <------><------>/* Wait for callbacks to appear. */ <------><------>trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("Sleep")); <------><------>swait_event_interruptible_exclusive(my_rdp->nocb_gp_wq, <------><------><------><------>!READ_ONCE(my_rdp->nocb_gp_sleep)); <------><------>trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("EndSleep")); <------>} else { <------><------>rnp = my_rdp->mynode; <------><------>trace_rcu_this_gp(rnp, my_rdp, wait_gp_seq, TPS("StartWait")); <------><------>swait_event_interruptible_exclusive( <------><------><------>rnp->nocb_gp_wq[rcu_seq_ctr(wait_gp_seq) & 0x1], <------><------><------>rcu_seq_done(&rnp->gp_seq, wait_gp_seq) || <------><------><------>!READ_ONCE(my_rdp->nocb_gp_sleep)); <------><------>trace_rcu_this_gp(rnp, my_rdp, wait_gp_seq, TPS("EndWait")); <------>} <------>if (!rcu_nocb_poll) { <------><------>raw_spin_lock_irqsave(&my_rdp->nocb_gp_lock, flags); <------><------>if (bypass) <------><------><------>del_timer(&my_rdp->nocb_bypass_timer); <------><------>WRITE_ONCE(my_rdp->nocb_gp_sleep, true); <------><------>raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags); <------>} <------>my_rdp->nocb_gp_seq = -1; <------>WARN_ON(signal_pending(current)); } /* * No-CBs grace-period-wait kthread. There is one of these per group * of CPUs, but only once at least one CPU in that group has come online * at least once since boot. This kthread checks for newly posted * callbacks from any of the CPUs it is responsible for, waits for a * grace period, then awakens all of the rcu_nocb_cb_kthread() instances * that then have callback-invocation work to do. */ static int rcu_nocb_gp_kthread(void *arg) { <------>struct rcu_data *rdp = arg; <------>for (;;) { <------><------>WRITE_ONCE(rdp->nocb_gp_loops, rdp->nocb_gp_loops + 1); <------><------>nocb_gp_wait(rdp); <------><------>cond_resched_tasks_rcu_qs(); <------>} <------>return 0; } /* * Invoke any ready callbacks from the corresponding no-CBs CPU, * then, if there are no more, wait for more to appear. */ static void nocb_cb_wait(struct rcu_data *rdp) { <------>unsigned long cur_gp_seq; <------>unsigned long flags; <------>bool needwake_gp = false; <------>struct rcu_node *rnp = rdp->mynode; <------>local_irq_save(flags); <------>rcu_momentary_dyntick_idle(); <------>local_irq_restore(flags); <------>local_bh_disable(); <------>rcu_do_batch(rdp); <------>local_bh_enable(); <------>lockdep_assert_irqs_enabled(); <------>rcu_nocb_lock_irqsave(rdp, flags); <------>if (rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq) && <------> rcu_seq_done(&rnp->gp_seq, cur_gp_seq) && <------> raw_spin_trylock_rcu_node(rnp)) { /* irqs already disabled. */ <------><------>needwake_gp = rcu_advance_cbs(rdp->mynode, rdp); <------><------>raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ <------>} <------>if (rcu_segcblist_ready_cbs(&rdp->cblist)) { <------><------>rcu_nocb_unlock_irqrestore(rdp, flags); <------><------>if (needwake_gp) <------><------><------>rcu_gp_kthread_wake(); <------><------>return; <------>} <------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("CBSleep")); <------>WRITE_ONCE(rdp->nocb_cb_sleep, true); <------>rcu_nocb_unlock_irqrestore(rdp, flags); <------>if (needwake_gp) <------><------>rcu_gp_kthread_wake(); <------>swait_event_interruptible_exclusive(rdp->nocb_cb_wq, <------><------><------><------> !READ_ONCE(rdp->nocb_cb_sleep)); <------>if (!smp_load_acquire(&rdp->nocb_cb_sleep)) { /* VVV */ <------><------>/* ^^^ Ensure CB invocation follows _sleep test. */ <------><------>return; <------>} <------>WARN_ON(signal_pending(current)); <------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WokeEmpty")); } /* * Per-rcu_data kthread, but only for no-CBs CPUs. Repeatedly invoke * nocb_cb_wait() to do the dirty work. */ static int rcu_nocb_cb_kthread(void *arg) { <------>struct rcu_data *rdp = arg; <------>// Each pass through this loop does one callback batch, and, <------>// if there are no more ready callbacks, waits for them. <------>for (;;) { <------><------>nocb_cb_wait(rdp); <------><------>cond_resched_tasks_rcu_qs(); <------>} <------>return 0; } /* Is a deferred wakeup of rcu_nocb_kthread() required? */ static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) { <------>return READ_ONCE(rdp->nocb_defer_wakeup); } /* Do a deferred wakeup of rcu_nocb_kthread(). */ static void do_nocb_deferred_wakeup_common(struct rcu_data *rdp) { <------>unsigned long flags; <------>int ndw; <------>rcu_nocb_lock_irqsave(rdp, flags); <------>if (!rcu_nocb_need_deferred_wakeup(rdp)) { <------><------>rcu_nocb_unlock_irqrestore(rdp, flags); <------><------>return; <------>} <------>ndw = READ_ONCE(rdp->nocb_defer_wakeup); <------>wake_nocb_gp(rdp, ndw == RCU_NOCB_WAKE_FORCE, flags); <------>trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("DeferredWake")); } /* Do a deferred wakeup of rcu_nocb_kthread() from a timer handler. */ static void do_nocb_deferred_wakeup_timer(struct timer_list *t) { <------>struct rcu_data *rdp = from_timer(rdp, t, nocb_timer); <------>do_nocb_deferred_wakeup_common(rdp); } /* * Do a deferred wakeup of rcu_nocb_kthread() from fastpath. * This means we do an inexact common-case check. Note that if * we miss, ->nocb_timer will eventually clean things up. */ static void do_nocb_deferred_wakeup(struct rcu_data *rdp) { <------>if (rcu_nocb_need_deferred_wakeup(rdp)) <------><------>do_nocb_deferred_wakeup_common(rdp); } void rcu_nocb_flush_deferred_wakeup(void) { <------>do_nocb_deferred_wakeup(this_cpu_ptr(&rcu_data)); } void __init rcu_init_nohz(void) { <------>int cpu; <------>bool need_rcu_nocb_mask = false; <------>struct rcu_data *rdp; #if defined(CONFIG_NO_HZ_FULL) <------>if (tick_nohz_full_running && cpumask_weight(tick_nohz_full_mask)) <------><------>need_rcu_nocb_mask = true; #endif /* #if defined(CONFIG_NO_HZ_FULL) */ <------>if (!cpumask_available(rcu_nocb_mask) && need_rcu_nocb_mask) { <------><------>if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) { <------><------><------>pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n"); <------><------><------>return; <------><------>} <------>} <------>if (!cpumask_available(rcu_nocb_mask)) <------><------>return; #if defined(CONFIG_NO_HZ_FULL) <------>if (tick_nohz_full_running) <------><------>cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); #endif /* #if defined(CONFIG_NO_HZ_FULL) */ <------>if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { <------><------>pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n"); <------><------>cpumask_and(rcu_nocb_mask, cpu_possible_mask, <------><------><------> rcu_nocb_mask); <------>} <------>if (cpumask_empty(rcu_nocb_mask)) <------><------>pr_info("\tOffload RCU callbacks from CPUs: (none).\n"); <------>else <------><------>pr_info("\tOffload RCU callbacks from CPUs: %*pbl.\n", <------><------><------>cpumask_pr_args(rcu_nocb_mask)); <------>if (rcu_nocb_poll) <------><------>pr_info("\tPoll for callbacks from no-CBs CPUs.\n"); <------>for_each_cpu(cpu, rcu_nocb_mask) { <------><------>rdp = per_cpu_ptr(&rcu_data, cpu); <------><------>if (rcu_segcblist_empty(&rdp->cblist)) <------><------><------>rcu_segcblist_init(&rdp->cblist); <------><------>rcu_segcblist_offload(&rdp->cblist); <------>} <------>rcu_organize_nocb_kthreads(); } /* Initialize per-rcu_data variables for no-CBs CPUs. */ static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) { <------>init_swait_queue_head(&rdp->nocb_cb_wq); <------>init_swait_queue_head(&rdp->nocb_gp_wq); <------>raw_spin_lock_init(&rdp->nocb_lock); <------>raw_spin_lock_init(&rdp->nocb_bypass_lock); <------>raw_spin_lock_init(&rdp->nocb_gp_lock); <------>timer_setup(&rdp->nocb_timer, do_nocb_deferred_wakeup_timer, 0); <------>timer_setup(&rdp->nocb_bypass_timer, do_nocb_bypass_wakeup_timer, 0); <------>rcu_cblist_init(&rdp->nocb_bypass); } /* * If the specified CPU is a no-CBs CPU that does not already have its * rcuo CB kthread, spawn it. Additionally, if the rcuo GP kthread * for this CPU's group has not yet been created, spawn it as well. */ static void rcu_spawn_one_nocb_kthread(int cpu) { <------>struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); <------>struct rcu_data *rdp_gp; <------>struct task_struct *t; <------>/* <------> * If this isn't a no-CBs CPU or if it already has an rcuo kthread, <------> * then nothing to do. <------> */ <------>if (!rcu_is_nocb_cpu(cpu) || rdp->nocb_cb_kthread) <------><------>return; <------>/* If we didn't spawn the GP kthread first, reorganize! */ <------>rdp_gp = rdp->nocb_gp_rdp; <------>if (!rdp_gp->nocb_gp_kthread) { <------><------>t = kthread_run(rcu_nocb_gp_kthread, rdp_gp, <------><------><------><------>"rcuog/%d", rdp_gp->cpu); <------><------>if (WARN_ONCE(IS_ERR(t), "%s: Could not start rcuo GP kthread, OOM is now expected behavior\n", __func__)) <------><------><------>return; <------><------>WRITE_ONCE(rdp_gp->nocb_gp_kthread, t); <------>} <------>/* Spawn the kthread for this CPU. */ <------>t = kthread_run(rcu_nocb_cb_kthread, rdp, <------><------><------>"rcuo%c/%d", rcu_state.abbr, cpu); <------>if (WARN_ONCE(IS_ERR(t), "%s: Could not start rcuo CB kthread, OOM is now expected behavior\n", __func__)) <------><------>return; <------>WRITE_ONCE(rdp->nocb_cb_kthread, t); <------>WRITE_ONCE(rdp->nocb_gp_kthread, rdp_gp->nocb_gp_kthread); } /* * If the specified CPU is a no-CBs CPU that does not already have its * rcuo kthread, spawn it. */ static void rcu_spawn_cpu_nocb_kthread(int cpu) { <------>if (rcu_scheduler_fully_active) <------><------>rcu_spawn_one_nocb_kthread(cpu); } /* * Once the scheduler is running, spawn rcuo kthreads for all online * no-CBs CPUs. This assumes that the early_initcall()s happen before * non-boot CPUs come online -- if this changes, we will need to add * some mutual exclusion. */ static void __init rcu_spawn_nocb_kthreads(void) { <------>int cpu; <------>for_each_online_cpu(cpu) <------><------>rcu_spawn_cpu_nocb_kthread(cpu); } /* How many CB CPU IDs per GP kthread? Default of -1 for sqrt(nr_cpu_ids). */ static int rcu_nocb_gp_stride = -1; module_param(rcu_nocb_gp_stride, int, 0444); /* * Initialize GP-CB relationships for all no-CBs CPU. */ static void __init rcu_organize_nocb_kthreads(void) { <------>int cpu; <------>bool firsttime = true; <------>bool gotnocbs = false; <------>bool gotnocbscbs = true; <------>int ls = rcu_nocb_gp_stride; <------>int nl = 0; /* Next GP kthread. */ <------>struct rcu_data *rdp; <------>struct rcu_data *rdp_gp = NULL; /* Suppress misguided gcc warn. */ <------>struct rcu_data *rdp_prev = NULL; <------>if (!cpumask_available(rcu_nocb_mask)) <------><------>return; <------>if (ls == -1) { <------><------>ls = nr_cpu_ids / int_sqrt(nr_cpu_ids); <------><------>rcu_nocb_gp_stride = ls; <------>} <------>/* <------> * Each pass through this loop sets up one rcu_data structure. <------> * Should the corresponding CPU come online in the future, then <------> * we will spawn the needed set of rcu_nocb_kthread() kthreads. <------> */ <------>for_each_cpu(cpu, rcu_nocb_mask) { <------><------>rdp = per_cpu_ptr(&rcu_data, cpu); <------><------>if (rdp->cpu >= nl) { <------><------><------>/* New GP kthread, set up for CBs & next GP. */ <------><------><------>gotnocbs = true; <------><------><------>nl = DIV_ROUND_UP(rdp->cpu + 1, ls) * ls; <------><------><------>rdp->nocb_gp_rdp = rdp; <------><------><------>rdp_gp = rdp; <------><------><------>if (dump_tree) { <------><------><------><------>if (!firsttime) <------><------><------><------><------>pr_cont("%s\n", gotnocbscbs <------><------><------><------><------><------><------>? "" : " (self only)"); <------><------><------><------>gotnocbscbs = false; <------><------><------><------>firsttime = false; <------><------><------><------>pr_alert("%s: No-CB GP kthread CPU %d:", <------><------><------><------><------> __func__, cpu); <------><------><------>} <------><------>} else { <------><------><------>/* Another CB kthread, link to previous GP kthread. */ <------><------><------>gotnocbscbs = true; <------><------><------>rdp->nocb_gp_rdp = rdp_gp; <------><------><------>rdp_prev->nocb_next_cb_rdp = rdp; <------><------><------>if (dump_tree) <------><------><------><------>pr_cont(" %d", cpu); <------><------>} <------><------>rdp_prev = rdp; <------>} <------>if (gotnocbs && dump_tree) <------><------>pr_cont("%s\n", gotnocbscbs ? "" : " (self only)"); } /* * Bind the current task to the offloaded CPUs. If there are no offloaded * CPUs, leave the task unbound. Splat if the bind attempt fails. */ void rcu_bind_current_to_nocb(void) { <------>if (cpumask_available(rcu_nocb_mask) && cpumask_weight(rcu_nocb_mask)) <------><------>WARN_ON(sched_setaffinity(current->pid, rcu_nocb_mask)); } EXPORT_SYMBOL_GPL(rcu_bind_current_to_nocb); /* * Dump out nocb grace-period kthread state for the specified rcu_data * structure. */ static void show_rcu_nocb_gp_state(struct rcu_data *rdp) { <------>struct rcu_node *rnp = rdp->mynode; <------>pr_info("nocb GP %d %c%c%c%c%c%c %c[%c%c] %c%c:%ld rnp %d:%d %lu\n", <------><------>rdp->cpu, <------><------>"kK"[!!rdp->nocb_gp_kthread], <------><------>"lL"[raw_spin_is_locked(&rdp->nocb_gp_lock)], <------><------>"dD"[!!rdp->nocb_defer_wakeup], <------><------>"tT"[timer_pending(&rdp->nocb_timer)], <------><------>"bB"[timer_pending(&rdp->nocb_bypass_timer)], <------><------>"sS"[!!rdp->nocb_gp_sleep], <------><------>".W"[swait_active(&rdp->nocb_gp_wq)], <------><------>".W"[swait_active(&rnp->nocb_gp_wq[0])], <------><------>".W"[swait_active(&rnp->nocb_gp_wq[1])], <------><------>".B"[!!rdp->nocb_gp_bypass], <------><------>".G"[!!rdp->nocb_gp_gp], <------><------>(long)rdp->nocb_gp_seq, <------><------>rnp->grplo, rnp->grphi, READ_ONCE(rdp->nocb_gp_loops)); } /* Dump out nocb kthread state for the specified rcu_data structure. */ static void show_rcu_nocb_state(struct rcu_data *rdp) { <------>struct rcu_segcblist *rsclp = &rdp->cblist; <------>bool waslocked; <------>bool wastimer; <------>bool wassleep; <------>if (rdp->nocb_gp_rdp == rdp) <------><------>show_rcu_nocb_gp_state(rdp); <------>pr_info(" CB %d->%d %c%c%c%c%c%c F%ld L%ld C%d %c%c%c%c%c q%ld\n", <------><------>rdp->cpu, rdp->nocb_gp_rdp->cpu, <------><------>"kK"[!!rdp->nocb_cb_kthread], <------><------>"bB"[raw_spin_is_locked(&rdp->nocb_bypass_lock)], <------><------>"cC"[!!atomic_read(&rdp->nocb_lock_contended)], <------><------>"lL"[raw_spin_is_locked(&rdp->nocb_lock)], <------><------>"sS"[!!rdp->nocb_cb_sleep], <------><------>".W"[swait_active(&rdp->nocb_cb_wq)], <------><------>jiffies - rdp->nocb_bypass_first, <------><------>jiffies - rdp->nocb_nobypass_last, <------><------>rdp->nocb_nobypass_count, <------><------>".D"[rcu_segcblist_ready_cbs(rsclp)], <------><------>".W"[!rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL)], <------><------>".R"[!rcu_segcblist_restempty(rsclp, RCU_WAIT_TAIL)], <------><------>".N"[!rcu_segcblist_restempty(rsclp, RCU_NEXT_READY_TAIL)], <------><------>".B"[!!rcu_cblist_n_cbs(&rdp->nocb_bypass)], <------><------>rcu_segcblist_n_cbs(&rdp->cblist)); <------>/* It is OK for GP kthreads to have GP state. */ <------>if (rdp->nocb_gp_rdp == rdp) <------><------>return; <------>waslocked = raw_spin_is_locked(&rdp->nocb_gp_lock); <------>wastimer = timer_pending(&rdp->nocb_bypass_timer); <------>wassleep = swait_active(&rdp->nocb_gp_wq); <------>if (!rdp->nocb_gp_sleep && !waslocked && !wastimer && !wassleep) <------><------>return; /* Nothing untowards. */ <------>pr_info(" nocb GP activity on CB-only CPU!!! %c%c%c%c %c\n", <------><------>"lL"[waslocked], <------><------>"dD"[!!rdp->nocb_defer_wakeup], <------><------>"tT"[wastimer], <------><------>"sS"[!!rdp->nocb_gp_sleep], <------><------>".W"[wassleep]); } #else /* #ifdef CONFIG_RCU_NOCB_CPU */ /* No ->nocb_lock to acquire. */ static void rcu_nocb_lock(struct rcu_data *rdp) { } /* No ->nocb_lock to release. */ static void rcu_nocb_unlock(struct rcu_data *rdp) { } /* No ->nocb_lock to release. */ static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp, <------><------><------><------> unsigned long flags) { <------>local_irq_restore(flags); } /* Lockdep check that ->cblist may be safely accessed. */ static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp) { <------>lockdep_assert_irqs_disabled(); } static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq) { } static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp) { <------>return NULL; } static void rcu_init_one_nocb(struct rcu_node *rnp) { } static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp, <------><------><------><------> unsigned long j) { <------>return true; } static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp, <------><------><------><------>bool *was_alldone, unsigned long flags) { <------>return false; } static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty, <------><------><------><------> unsigned long flags) { <------>WARN_ON_ONCE(1); /* Should be dead code! */ } static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) { } static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) { <------>return false; } static void do_nocb_deferred_wakeup(struct rcu_data *rdp) { } static void rcu_spawn_cpu_nocb_kthread(int cpu) { } static void __init rcu_spawn_nocb_kthreads(void) { } static void show_rcu_nocb_state(struct rcu_data *rdp) { } #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ /* * Is this CPU a NO_HZ_FULL CPU that should ignore RCU so that the * grace-period kthread will do force_quiescent_state() processing? * The idea is to avoid waking up RCU core processing on such a * CPU unless the grace period has extended for too long. * * This code relies on the fact that all NO_HZ_FULL CPUs are also * CONFIG_RCU_NOCB_CPU CPUs. */ static bool rcu_nohz_full_cpu(void) { #ifdef CONFIG_NO_HZ_FULL <------>if (tick_nohz_full_cpu(smp_processor_id()) && <------> (!rcu_gp_in_progress() || <------> time_before(jiffies, READ_ONCE(rcu_state.gp_start) + HZ))) <------><------>return true; #endif /* #ifdef CONFIG_NO_HZ_FULL */ <------>return false; } /* * Bind the RCU grace-period kthreads to the housekeeping CPU. */ static void rcu_bind_gp_kthread(void) { <------>if (!tick_nohz_full_enabled()) <------><------>return; <------>housekeeping_affine(current, HK_FLAG_RCU); } /* Record the current task on dyntick-idle entry. */ static __always_inline void rcu_dynticks_task_enter(void) { #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) <------>WRITE_ONCE(current->rcu_tasks_idle_cpu, smp_processor_id()); #endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */ } /* Record no current task on dyntick-idle exit. */ static __always_inline void rcu_dynticks_task_exit(void) { #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) <------>WRITE_ONCE(current->rcu_tasks_idle_cpu, -1); #endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */ } /* Turn on heavyweight RCU tasks trace readers on idle/user entry. */ static __always_inline void rcu_dynticks_task_trace_enter(void) { #ifdef CONFIG_TASKS_TRACE_RCU <------>if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB)) <------><------>current->trc_reader_special.b.need_mb = true; #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */ } /* Turn off heavyweight RCU tasks trace readers on idle/user exit. */ static __always_inline void rcu_dynticks_task_trace_exit(void) { #ifdef CONFIG_TASKS_TRACE_RCU <------>if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB)) <------><------>current->trc_reader_special.b.need_mb = false; #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */ }
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
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