^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) // SPDX-License-Identifier: GPL-2.0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) * Out-of-line refcount functions.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6) #include <linux/mutex.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7) #include <linux/refcount.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8) #include <linux/spinlock.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9) #include <linux/bug.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) #define REFCOUNT_WARN(str) WARN_ONCE(1, "refcount_t: " str ".\n")
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) void refcount_warn_saturate(refcount_t *r, enum refcount_saturation_type t)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) refcount_set(r, REFCOUNT_SATURATED);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) switch (t) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) case REFCOUNT_ADD_NOT_ZERO_OVF:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) REFCOUNT_WARN("saturated; leaking memory");
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) case REFCOUNT_ADD_OVF:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) REFCOUNT_WARN("saturated; leaking memory");
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) case REFCOUNT_ADD_UAF:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) REFCOUNT_WARN("addition on 0; use-after-free");
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) case REFCOUNT_SUB_UAF:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) REFCOUNT_WARN("underflow; use-after-free");
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) case REFCOUNT_DEC_LEAK:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) REFCOUNT_WARN("decrement hit 0; leaking memory");
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) default:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) REFCOUNT_WARN("unknown saturation event!?");
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) EXPORT_SYMBOL(refcount_warn_saturate);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) /**
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) * refcount_dec_if_one - decrement a refcount if it is 1
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) * @r: the refcount
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) * No atomic_t counterpart, it attempts a 1 -> 0 transition and returns the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) * success thereof.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46) * Like all decrement operations, it provides release memory order and provides
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) * a control dependency.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) * It can be used like a try-delete operator; this explicit case is provided
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50) * and not cmpxchg in generic, because that would allow implementing unsafe
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) * operations.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) * Return: true if the resulting refcount is 0, false otherwise
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55) bool refcount_dec_if_one(refcount_t *r)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57) int val = 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) return atomic_try_cmpxchg_release(&r->refs, &val, 0);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) EXPORT_SYMBOL(refcount_dec_if_one);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63) /**
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) * refcount_dec_not_one - decrement a refcount if it is not 1
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65) * @r: the refcount
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67) * No atomic_t counterpart, it decrements unless the value is 1, in which case
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68) * it will return false.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) * Was often done like: atomic_add_unless(&var, -1, 1)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72) * Return: true if the decrement operation was successful, false otherwise
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74) bool refcount_dec_not_one(refcount_t *r)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76) unsigned int new, val = atomic_read(&r->refs);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78) do {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79) if (unlikely(val == REFCOUNT_SATURATED))
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80) return true;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82) if (val == 1)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83) return false;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85) new = val - 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86) if (new > val) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87) WARN_ONCE(new > val, "refcount_t: underflow; use-after-free.\n");
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88) return true;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 91) } while (!atomic_try_cmpxchg_release(&r->refs, &val, new));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 92)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 93) return true;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 94) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 95) EXPORT_SYMBOL(refcount_dec_not_one);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 96)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 97) /**
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 98) * refcount_dec_and_mutex_lock - return holding mutex if able to decrement
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 99) * refcount to 0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100) * @r: the refcount
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101) * @lock: the mutex to be locked
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103) * Similar to atomic_dec_and_mutex_lock(), it will WARN on underflow and fail
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104) * to decrement when saturated at REFCOUNT_SATURATED.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106) * Provides release memory ordering, such that prior loads and stores are done
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107) * before, and provides a control dependency such that free() must come after.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108) * See the comment on top.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110) * Return: true and hold mutex if able to decrement refcount to 0, false
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111) * otherwise
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113) bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115) if (refcount_dec_not_one(r))
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116) return false;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118) mutex_lock(lock);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119) if (!refcount_dec_and_test(r)) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120) mutex_unlock(lock);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121) return false;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 122) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 123)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 124) return true;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 125) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 126) EXPORT_SYMBOL(refcount_dec_and_mutex_lock);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 127)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 128) /**
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 129) * refcount_dec_and_lock - return holding spinlock if able to decrement
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 130) * refcount to 0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 131) * @r: the refcount
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 132) * @lock: the spinlock to be locked
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 133) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 134) * Similar to atomic_dec_and_lock(), it will WARN on underflow and fail to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 135) * decrement when saturated at REFCOUNT_SATURATED.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 136) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 137) * Provides release memory ordering, such that prior loads and stores are done
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 138) * before, and provides a control dependency such that free() must come after.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 139) * See the comment on top.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 140) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 141) * Return: true and hold spinlock if able to decrement refcount to 0, false
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 142) * otherwise
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 143) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 144) bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 145) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 146) if (refcount_dec_not_one(r))
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 147) return false;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 148)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 149) spin_lock(lock);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 150) if (!refcount_dec_and_test(r)) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 151) spin_unlock(lock);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 152) return false;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 153) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 154)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 155) return true;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 156) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 157) EXPORT_SYMBOL(refcount_dec_and_lock);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 158)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 159) /**
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 160) * refcount_dec_and_lock_irqsave - return holding spinlock with disabled
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 161) * interrupts if able to decrement refcount to 0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 162) * @r: the refcount
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 163) * @lock: the spinlock to be locked
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 164) * @flags: saved IRQ-flags if the is acquired
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 165) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 166) * Same as refcount_dec_and_lock() above except that the spinlock is acquired
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 167) * with disabled interupts.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 168) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 169) * Return: true and hold spinlock if able to decrement refcount to 0, false
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 170) * otherwise
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 171) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 172) bool refcount_dec_and_lock_irqsave(refcount_t *r, spinlock_t *lock,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 173) unsigned long *flags)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 174) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 175) if (refcount_dec_not_one(r))
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 176) return false;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 177)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 178) spin_lock_irqsave(lock, *flags);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 179) if (!refcount_dec_and_test(r)) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 180) spin_unlock_irqrestore(lock, *flags);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 181) return false;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 182) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 183)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 184) return true;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 185) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 186) EXPORT_SYMBOL(refcount_dec_and_lock_irqsave);
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
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