diff options
| -rw-r--r-- | include/linux/percpu-refcount.h | 19 | ||||
| -rw-r--r-- | lib/percpu-refcount.c | 35 |
2 files changed, 54 insertions, 0 deletions
diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h index 0ddd2839ca84..3dfbf237cd8f 100644 --- a/include/linux/percpu-refcount.h +++ b/include/linux/percpu-refcount.h @@ -67,6 +67,7 @@ struct percpu_ref { int __must_check percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release); +void percpu_ref_reinit(struct percpu_ref *ref); void percpu_ref_exit(struct percpu_ref *ref); void percpu_ref_kill_and_confirm(struct percpu_ref *ref, percpu_ref_func_t *confirm_kill); @@ -99,6 +100,9 @@ static inline bool __pcpu_ref_alive(struct percpu_ref *ref, { unsigned long pcpu_ptr = ACCESS_ONCE(ref->pcpu_count_ptr); + /* paired with smp_store_release() in percpu_ref_reinit() */ + smp_read_barrier_depends(); + if (unlikely(pcpu_ptr & PCPU_REF_DEAD)) return false; @@ -206,4 +210,19 @@ static inline void percpu_ref_put(struct percpu_ref *ref) rcu_read_unlock_sched(); } +/** + * percpu_ref_is_zero - test whether a percpu refcount reached zero + * @ref: percpu_ref to test + * + * Returns %true if @ref reached zero. + */ +static inline bool percpu_ref_is_zero(struct percpu_ref *ref) +{ + unsigned __percpu *pcpu_count; + + if (__pcpu_ref_alive(ref, &pcpu_count)) + return false; + return !atomic_read(&ref->count); +} + #endif diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c index ac4299120087..fe5a3342e960 100644 --- a/lib/percpu-refcount.c +++ b/lib/percpu-refcount.c @@ -61,6 +61,41 @@ int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release) EXPORT_SYMBOL_GPL(percpu_ref_init); /** + * percpu_ref_reinit - re-initialize a percpu refcount + * @ref: perpcu_ref to re-initialize + * + * Re-initialize @ref so that it's in the same state as when it finished + * percpu_ref_init(). @ref must have been initialized successfully, killed + * and reached 0 but not exited. + * + * Note that percpu_ref_tryget[_live]() are safe to perform on @ref while + * this function is in progress. + */ +void percpu_ref_reinit(struct percpu_ref *ref) +{ + unsigned __percpu *pcpu_count = pcpu_count_ptr(ref); + int cpu; + + BUG_ON(!pcpu_count); + WARN_ON(!percpu_ref_is_zero(ref)); + + atomic_set(&ref->count, 1 + PCPU_COUNT_BIAS); + + /* + * Restore per-cpu operation. smp_store_release() is paired with + * smp_read_barrier_depends() in __pcpu_ref_alive() and guarantees + * that the zeroing is visible to all percpu accesses which can see + * the following PCPU_REF_DEAD clearing. + */ + for_each_possible_cpu(cpu) + *per_cpu_ptr(pcpu_count, cpu) = 0; + + smp_store_release(&ref->pcpu_count_ptr, + ref->pcpu_count_ptr & ~PCPU_REF_DEAD); +} +EXPORT_SYMBOL_GPL(percpu_ref_reinit); + +/** * percpu_ref_exit - undo percpu_ref_init() * @ref: percpu_ref to exit * |