lib/refcount.c

Source file repositories/reference/linux-study-clean/lib/refcount.c

File Facts

System
Linux kernel
Corpus path
lib/refcount.c
Extension
.c
Size
4884 bytes
Lines
187
Domain
Kernel Services
Bucket
lib
Inferred role
Kernel Services: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

Shared kernel service surface used by multiple subsystems, including helpers, cryptography, virtualization support, and async I/O infrastructure.

Dependency Surface

Detected Declarations

Annotated Snippet

if (new > val) {
			WARN_ONCE(new > val, "refcount_t: underflow; use-after-free.\n");
			return true;
		}

	} while (!atomic_try_cmpxchg_release(&r->refs, &val, new));

	return true;
}
EXPORT_SYMBOL(refcount_dec_not_one);

/**
 * refcount_dec_and_mutex_lock - return holding mutex if able to decrement
 *                               refcount to 0
 * @r: the refcount
 * @lock: the mutex to be locked
 *
 * Similar to atomic_dec_and_mutex_lock(), it will WARN on underflow and fail
 * to decrement when saturated at REFCOUNT_SATURATED.
 *
 * Provides release memory ordering, such that prior loads and stores are done
 * before, and provides a control dependency such that free() must come after.
 * See the comment on top.
 *
 * Return: true and hold mutex if able to decrement refcount to 0, false
 *         otherwise
 */
bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock)
{
	if (refcount_dec_not_one(r))
		return false;

	mutex_lock(lock);
	if (!refcount_dec_and_test(r)) {
		mutex_unlock(lock);
		return false;
	}

	return true;
}
EXPORT_SYMBOL(refcount_dec_and_mutex_lock);

/**
 * refcount_dec_and_lock - return holding spinlock if able to decrement
 *                         refcount to 0
 * @r: the refcount
 * @lock: the spinlock to be locked
 *
 * Similar to atomic_dec_and_lock(), it will WARN on underflow and fail to
 * decrement when saturated at REFCOUNT_SATURATED.
 *
 * Provides release memory ordering, such that prior loads and stores are done
 * before, and provides a control dependency such that free() must come after.
 * See the comment on top.
 *
 * Return: true and hold spinlock if able to decrement refcount to 0, false
 *         otherwise
 */
bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock)
{
	if (refcount_dec_not_one(r))
		return false;

	spin_lock(lock);
	if (!refcount_dec_and_test(r)) {
		spin_unlock(lock);
		return false;
	}

	return true;
}
EXPORT_SYMBOL(refcount_dec_and_lock);

/**
 * refcount_dec_and_lock_irqsave - return holding spinlock with disabled
 *                                 interrupts if able to decrement refcount to 0
 * @r: the refcount
 * @lock: the spinlock to be locked
 * @flags: saved IRQ-flags if the is acquired
 *
 * Same as refcount_dec_and_lock() above except that the spinlock is acquired
 * with disabled interrupts.
 *
 * Return: true and hold spinlock if able to decrement refcount to 0, false
 *         otherwise
 */
bool refcount_dec_and_lock_irqsave(refcount_t *r, spinlock_t *lock,
				   unsigned long *flags)
{
	if (refcount_dec_not_one(r))

Annotation

Implementation Notes