diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/percpu-refcount.c | 86 |
1 files changed, 54 insertions, 32 deletions
diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c index 963b7034a51b..fe5a3342e960 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 *)(ref->pcpu_count_ptr & ~PCPU_REF_DEAD); +} + /** * percpu_ref_init - initialize a percpu refcount * @ref: percpu_ref to initialize @@ -46,8 +51,8 @@ int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release) { atomic_set(&ref->count, 1 + PCPU_COUNT_BIAS); - ref->pcpu_count = alloc_percpu(unsigned); - if (!ref->pcpu_count) + ref->pcpu_count_ptr = (unsigned long)alloc_percpu(unsigned); + if (!ref->pcpu_count_ptr) return -ENOMEM; ref->release = release; @@ -56,53 +61,71 @@ int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release) EXPORT_SYMBOL_GPL(percpu_ref_init); /** - * percpu_ref_cancel_init - cancel percpu_ref_init() - * @ref: percpu_ref to cancel init for + * percpu_ref_reinit - re-initialize a percpu refcount + * @ref: perpcu_ref to re-initialize * - * Once a percpu_ref is initialized, its destruction is initiated by - * percpu_ref_kill() and completes asynchronously, which can be painful to - * do when destroying a half-constructed object in init failure path. + * 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. * - * This function destroys @ref without invoking @ref->release and the - * memory area containing it can be freed immediately on return. To - * prevent accidental misuse, it's required that @ref has finished - * percpu_ref_init(), whether successful or not, but never used. - * - * The weird name and usage restriction are to prevent people from using - * this function by mistake for normal shutdown instead of - * percpu_ref_kill(). + * Note that percpu_ref_tryget[_live]() are safe to perform on @ref while + * this function is in progress. */ -void percpu_ref_cancel_init(struct percpu_ref *ref) +void percpu_ref_reinit(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); + 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 + * + * This function exits @ref. The caller is responsible for ensuring that + * @ref is no longer in active use. The usual places to invoke this + * function from are the @ref->release() callback or in init failure path + * where percpu_ref_init() succeeded but other parts of the initialization + * of the embedding object failed. + */ +void percpu_ref_exit(struct percpu_ref *ref) +{ + unsigned __percpu *pcpu_count = pcpu_count_ptr(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); + ref->pcpu_count_ptr = PCPU_REF_DEAD; } } -EXPORT_SYMBOL_GPL(percpu_ref_cancel_init); +EXPORT_SYMBOL_GPL(percpu_ref_exit); 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_STATUS_MASK); - for_each_possible_cpu(cpu) count += *per_cpu_ptr(pcpu_count, cpu); - free_percpu(pcpu_count); - pr_debug("global %i pcpu %i", atomic_read(&ref->count), (int) count); /* @@ -152,11 +175,10 @@ 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(ref->pcpu_count_ptr & PCPU_REF_DEAD, "percpu_ref_kill() called more than once!\n"); - ref->pcpu_count = (unsigned __percpu *) - (((unsigned long) ref->pcpu_count)|PCPU_REF_DEAD); + ref->pcpu_count_ptr |= PCPU_REF_DEAD; ref->confirm_kill = confirm_kill; call_rcu_sched(&ref->rcu, percpu_ref_kill_rcu); |