diff options
| -rw-r--r-- | include/linux/percpu-refcount.h | 35 | ||||
| -rw-r--r-- | lib/percpu-refcount.c | 17 |
2 files changed, 30 insertions, 22 deletions
diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h index bfdeb0d4..b62a4ee 100644 --- a/include/linux/percpu-refcount.h +++ b/include/linux/percpu-refcount.h @@ -88,10 +88,25 @@ static inline void percpu_ref_kill(struct percpu_ref *ref) return percpu_ref_kill_and_confirm(ref, NULL); } -#define PCPU_REF_PTR 0 #define PCPU_REF_DEAD 1 -#define REF_STATUS(count) (((unsigned long) count) & PCPU_REF_DEAD) +/* + * Internal helper. Don't use outside percpu-refcount proper. The + * function doesn't return the pointer and let the caller test it for NULL + * because doing so forces the compiler to generate two conditional + * branches as it can't assume that @ref->pcpu_count is not NULL. + */ +static inline bool __pcpu_ref_alive(struct percpu_ref *ref, + unsigned __percpu **pcpu_countp) +{ + unsigned long pcpu_ptr = (unsigned long)ACCESS_ONCE(ref->pcpu_count); + + if (unlikely(pcpu_ptr & PCPU_REF_DEAD)) + return false; + + *pcpu_countp = (unsigned __percpu *)pcpu_ptr; + return true; +} /** * percpu_ref_get - increment a percpu refcount @@ -105,9 +120,7 @@ static inline void percpu_ref_get(struct percpu_ref *ref) rcu_read_lock_sched(); - pcpu_count = ACCESS_ONCE(ref->pcpu_count); - - if (likely(REF_STATUS(pcpu_count) == PCPU_REF_PTR)) + if (__pcpu_ref_alive(ref, &pcpu_count)) this_cpu_inc(*pcpu_count); else atomic_inc(&ref->count); @@ -131,9 +144,7 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref) rcu_read_lock_sched(); - pcpu_count = ACCESS_ONCE(ref->pcpu_count); - - if (likely(REF_STATUS(pcpu_count) == PCPU_REF_PTR)) { + if (__pcpu_ref_alive(ref, &pcpu_count)) { this_cpu_inc(*pcpu_count); ret = true; } else { @@ -166,9 +177,7 @@ static inline bool percpu_ref_tryget_live(struct percpu_ref *ref) rcu_read_lock_sched(); - pcpu_count = ACCESS_ONCE(ref->pcpu_count); - - if (likely(REF_STATUS(pcpu_count) == PCPU_REF_PTR)) { + if (__pcpu_ref_alive(ref, &pcpu_count)) { this_cpu_inc(*pcpu_count); ret = true; } @@ -191,9 +200,7 @@ static inline void percpu_ref_put(struct percpu_ref *ref) rcu_read_lock_sched(); - pcpu_count = ACCESS_ONCE(ref->pcpu_count); - - if (likely(REF_STATUS(pcpu_count) == PCPU_REF_PTR)) + if (__pcpu_ref_alive(ref, &pcpu_count)) this_cpu_dec(*pcpu_count); else if (unlikely(atomic_dec_and_test(&ref->count))) ref->release(ref); diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c index 17bce2b..087f1a0 100644 --- a/lib/percpu-refcount.c +++ b/lib/percpu-refcount.c @@ -31,6 +31,11 @@ #define PCPU_COUNT_BIAS (1U << 31) +static unsigned __percpu *pcpu_count_ptr(struct percpu_ref *ref) +{ + return (unsigned __percpu *)((unsigned long)ref->pcpu_count & ~PCPU_REF_DEAD); +} + /** * percpu_ref_init - initialize a percpu refcount * @ref: percpu_ref to initialize @@ -74,7 +79,7 @@ EXPORT_SYMBOL_GPL(percpu_ref_init); */ void percpu_ref_cancel_init(struct percpu_ref *ref) { - unsigned __percpu *pcpu_count = ref->pcpu_count; + unsigned __percpu *pcpu_count = pcpu_count_ptr(ref); int cpu; WARN_ON_ONCE(atomic_read(&ref->count) != 1 + PCPU_COUNT_BIAS); @@ -82,7 +87,7 @@ void percpu_ref_cancel_init(struct percpu_ref *ref) if (pcpu_count) { for_each_possible_cpu(cpu) WARN_ON_ONCE(*per_cpu_ptr(pcpu_count, cpu)); - free_percpu(ref->pcpu_count); + free_percpu(pcpu_count); } } EXPORT_SYMBOL_GPL(percpu_ref_cancel_init); @@ -90,14 +95,10 @@ EXPORT_SYMBOL_GPL(percpu_ref_cancel_init); static void percpu_ref_kill_rcu(struct rcu_head *rcu) { struct percpu_ref *ref = container_of(rcu, struct percpu_ref, rcu); - unsigned __percpu *pcpu_count = ref->pcpu_count; + unsigned __percpu *pcpu_count = pcpu_count_ptr(ref); unsigned count = 0; int cpu; - /* Mask out PCPU_REF_DEAD */ - pcpu_count = (unsigned __percpu *) - (((unsigned long) pcpu_count) & ~PCPU_REF_DEAD); - for_each_possible_cpu(cpu) count += *per_cpu_ptr(pcpu_count, cpu); @@ -152,7 +153,7 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu) void percpu_ref_kill_and_confirm(struct percpu_ref *ref, percpu_ref_func_t *confirm_kill) { - WARN_ONCE(REF_STATUS(ref->pcpu_count) == PCPU_REF_DEAD, + WARN_ONCE((unsigned long)ref->pcpu_count & PCPU_REF_DEAD, "percpu_ref_kill() called more than once!\n"); ref->pcpu_count = (unsigned __percpu *) |
