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Commit 6251f997 authored by Tejun Heo's avatar Tejun Heo
Browse files

percpu_ref: minor code and comment updates 



* Some comments became stale.  Updated.
* percpu_ref_tryget() unnecessarily initializes @ret.  Removed.
* A blank line removed from percpu_ref_kill_rcu().
* Explicit function name in a WARN format string replaced with __func__.
* WARN_ON() in percpu_ref_reinit() converted to WARN_ON_ONCE().

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarKent Overstreet <kmo@daterainc.com>
parent a2237370

include/linux/percpu-refcount.h

+16 −9
Original line number Diff line number Diff line
@@ -115,7 +115,9 @@ static inline bool __pcpu_ref_alive(struct percpu_ref *ref, 
 * percpu_ref_get - increment a percpu refcount

 * @ref: percpu_ref to get

 *

 * Analagous to atomic_inc().

 * Analagous to atomic_long_inc().

 *

 * This function is safe to call as long as @ref is between init and exit.

 */

static inline void percpu_ref_get(struct percpu_ref *ref)

{
@@ -138,12 +140,12 @@ static inline void percpu_ref_get(struct percpu_ref *ref) 
 * Increment a percpu refcount unless its count already reached zero.

 * Returns %true on success; %false on failure.

 *

 * The caller is responsible for ensuring that @ref stays accessible.

 * This function is safe to call as long as @ref is between init and exit.

 */

static inline bool percpu_ref_tryget(struct percpu_ref *ref)

{

	unsigned long __percpu *pcpu_count;

	int ret = false;

	int ret;



	rcu_read_lock_sched();
@@ -166,12 +168,13 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref) 
 * Increment a percpu refcount unless it has already been killed.  Returns

 * %true on success; %false on failure.

 *

 * Completion of percpu_ref_kill() in itself doesn't guarantee that tryget

 * will fail.  For such guarantee, percpu_ref_kill_and_confirm() should be

 * used.  After the confirm_kill callback is invoked, it's guaranteed that

 * no new reference will be given out by percpu_ref_tryget().

 * Completion of percpu_ref_kill() in itself doesn't guarantee that this

 * function will fail.  For such guarantee, percpu_ref_kill_and_confirm()

 * should be used.  After the confirm_kill callback is invoked, it's

 * guaranteed that no new reference will be given out by

 * percpu_ref_tryget_live().

 *

 * The caller is responsible for ensuring that @ref stays accessible.

 * This function is safe to call as long as @ref is between init and exit.

 */

static inline bool percpu_ref_tryget_live(struct percpu_ref *ref)

{
@@ -196,6 +199,8 @@ static inline bool percpu_ref_tryget_live(struct percpu_ref *ref) 
 *

 * Decrement the refcount, and if 0, call the release function (which was passed

 * to percpu_ref_init())

 *

 * This function is safe to call as long as @ref is between init and exit.

 */

static inline void percpu_ref_put(struct percpu_ref *ref)

{
@@ -216,6 +221,8 @@ static inline void percpu_ref_put(struct percpu_ref *ref) 
 * @ref: percpu_ref to test

 *

 * Returns %true if @ref reached zero.

 *

 * This function is safe to call as long as @ref is between init and exit.

 */

static inline bool percpu_ref_is_zero(struct percpu_ref *ref)

{

lib/percpu-refcount.c

+6 −8
Original line number Diff line number Diff line
@@ -108,7 +108,6 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu) 
	 * reaching 0 before we add the percpu counts. But doing it at the same

	 * time is equivalent and saves us atomic operations:

	 */



	atomic_long_add((long)count - PCPU_COUNT_BIAS, &ref->count);



	WARN_ONCE(atomic_long_read(&ref->count) <= 0,
@@ -120,8 +119,8 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu) 
		ref->confirm_kill(ref);



	/*

	 * Now we're in single atomic_t mode with a consistent refcount, so it's

	 * safe to drop our initial ref:

	 * Now we're in single atomic_long_t mode with a consistent

	 * refcount, so it's safe to drop our initial ref:

	 */

	percpu_ref_put(ref);

}
@@ -134,8 +133,8 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu) 
 * Equivalent to percpu_ref_kill() but also schedules kill confirmation if

 * @confirm_kill is not NULL.  @confirm_kill, which may not block, will be

 * called after @ref is seen as dead from all CPUs - all further

 * invocations of percpu_ref_tryget() will fail.  See percpu_ref_tryget()

 * for more details.

 * invocations of percpu_ref_tryget_live() will fail.  See

 * percpu_ref_tryget_live() for more details.

 *

 * Due to the way percpu_ref is implemented, @confirm_kill will be called

 * after at least one full RCU grace period has passed but this is an
@@ -145,8 +144,7 @@ void percpu_ref_kill_and_confirm(struct percpu_ref *ref, 
				 percpu_ref_func_t *confirm_kill)

{

	WARN_ONCE(ref->pcpu_count_ptr & PCPU_REF_DEAD,

		  "percpu_ref_kill() called more than once on %pf!",

		  ref->release);

		  "%s called more than once on %pf!", __func__, ref->release);



	ref->pcpu_count_ptr |= PCPU_REF_DEAD;

	ref->confirm_kill = confirm_kill;
@@ -172,7 +170,7 @@ void percpu_ref_reinit(struct percpu_ref *ref) 
	int cpu;



	BUG_ON(!pcpu_count);

	WARN_ON(!percpu_ref_is_zero(ref));

	WARN_ON_ONCE(!percpu_ref_is_zero(ref));



	atomic_long_set(&ref->count, 1 + PCPU_COUNT_BIAS);