On Tue, Sep 23, 2014 at 01:55:11AM -0400, Tejun Heo wrote: > * 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 <[email protected]> > Cc: Kent Overstreet <[email protected]>
Reviewed-by: Kent Overstreet <[email protected]> > --- > include/linux/percpu-refcount.h | 25 ++++++++++++++++--------- > lib/percpu-refcount.c | 14 ++++++-------- > 2 files changed, 22 insertions(+), 17 deletions(-) > > diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h > index f015f13..d44b027 100644 > --- a/include/linux/percpu-refcount.h > +++ b/include/linux/percpu-refcount.h > @@ -115,8 +115,10 @@ 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) > { > unsigned long __percpu *pcpu_count; > @@ -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) > { > diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c > index 070dab5..8ef3f5c 100644 > --- a/lib/percpu-refcount.c > +++ b/lib/percpu-refcount.c > @@ -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); > > -- > 1.9.3 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
