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percpu_ref: minor code and comment updates

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* 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: Tejun Heo <tj@kernel.org>
Reviewed-by: Kent Overstreet <kmo@daterainc.com>
This commit is contained in:
Tejun Heo 2014-09-24 13:31:48 -04:00
parent a223737019
commit 6251f9976a
2 changed files with 22 additions and 17 deletions
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23
include/linux/percpu-refcount.h
View File

@ -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)
{

14
lib/percpu-refcount.c
View File

@ -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);