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percpu-refcount: Introduce percpu_ref_resurrect()

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This function will be used in a later patch to switch the struct
request_queue q_usage_counter from killed back to live. In contrast
to percpu_ref_reinit(), this new function does not require that the
refcount is zero.

Signed-off-by: Bart Van Assche <[email protected]>
Acked-by: Tejun Heo <[email protected]>
Reviewed-by: Ming Lei <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Jianchao Wang <[email protected]>
Cc: Hannes Reinecke <[email protected]>
Cc: Johannes Thumshirn <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
Bart Van Assche 2018-09-26 14:01:07 -07:00 • committed by Jens Axboe
commit 18c9a6bbe0
2 changed files with 27 additions and 2 deletions
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28
lib/percpu-refcount.c
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@ -356,11 +356,35 @@ EXPORT_SYMBOL_GPL(percpu_ref_kill_and_confirm);
*/
void percpu_ref_reinit(struct percpu_ref *ref)
{
WARN_ON_ONCE(!percpu_ref_is_zero(ref));
percpu_ref_resurrect(ref);
}
EXPORT_SYMBOL_GPL(percpu_ref_reinit);
/**
* percpu_ref_resurrect - modify a percpu refcount from dead to live
* @ref: perpcu_ref to resurrect
*
* Modify @ref so that it's in the same state as before percpu_ref_kill() was
* called. @ref must be dead but must not yet have exited.
*
* If @ref->release() frees @ref then the caller is responsible for
* guaranteeing that @ref->release() does not get called while this
* function is in progress.
*
* Note that percpu_ref_tryget[_live]() are safe to perform on @ref while
* this function is in progress.
*/
void percpu_ref_resurrect(struct percpu_ref *ref)
{
unsigned long __percpu *percpu_count;
unsigned long flags;
spin_lock_irqsave(&percpu_ref_switch_lock, flags);
WARN_ON_ONCE(!percpu_ref_is_zero(ref));
WARN_ON_ONCE(!(ref->percpu_count_ptr & __PERCPU_REF_DEAD));
WARN_ON_ONCE(__ref_is_percpu(ref, &percpu_count));
ref->percpu_count_ptr &= ~__PERCPU_REF_DEAD;
percpu_ref_get(ref);
@ -368,4 +392,4 @@ void percpu_ref_reinit(struct percpu_ref *ref)
spin_unlock_irqrestore(&percpu_ref_switch_lock, flags);
}
EXPORT_SYMBOL_GPL(percpu_ref_reinit);
EXPORT_SYMBOL_GPL(percpu_ref_resurrect);