diff options
| -rw-r--r-- | include/linux/percpu-refcount.h | 3 | ||||
| -rw-r--r-- | lib/percpu-refcount.c | 73 |
2 files changed, 56 insertions, 20 deletions
diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h index d1252e1..cd7e20f 100644 --- a/include/linux/percpu-refcount.h +++ b/include/linux/percpu-refcount.h @@ -80,9 +80,10 @@ int __must_check percpu_ref_init(struct percpu_ref *ref, void percpu_ref_exit(struct percpu_ref *ref); void percpu_ref_switch_to_atomic(struct percpu_ref *ref, percpu_ref_func_t *confirm_switch); -void percpu_ref_reinit(struct percpu_ref *ref); +void percpu_ref_switch_to_percpu(struct percpu_ref *ref); void percpu_ref_kill_and_confirm(struct percpu_ref *ref, percpu_ref_func_t *confirm_kill); +void percpu_ref_reinit(struct percpu_ref *ref); /** * percpu_ref_kill - drop the initial ref diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c index 6e0d143..5a6d43b 100644 --- a/lib/percpu-refcount.c +++ b/lib/percpu-refcount.c @@ -206,40 +206,54 @@ void percpu_ref_switch_to_atomic(struct percpu_ref *ref, __percpu_ref_switch_to_atomic(ref, confirm_switch); } -/** - * 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) +static void __percpu_ref_switch_to_percpu(struct percpu_ref *ref) { unsigned long __percpu *percpu_count = percpu_count_ptr(ref); int cpu; BUG_ON(!percpu_count); - WARN_ON_ONCE(!percpu_ref_is_zero(ref)); - atomic_long_set(&ref->count, 1 + PERCPU_COUNT_BIAS); + if (!(ref->percpu_count_ptr & __PERCPU_REF_ATOMIC)) + return; + + wait_event(percpu_ref_switch_waitq, !ref->confirm_switch); + + atomic_long_add(PERCPU_COUNT_BIAS, &ref->count); /* * Restore per-cpu operation. smp_store_release() is paired with * smp_read_barrier_depends() in __ref_is_percpu() and guarantees * that the zeroing is visible to all percpu accesses which can see - * the following __PERCPU_REF_ATOMIC_DEAD clearing. + * the following __PERCPU_REF_ATOMIC clearing. */ for_each_possible_cpu(cpu) *per_cpu_ptr(percpu_count, cpu) = 0; smp_store_release(&ref->percpu_count_ptr, - ref->percpu_count_ptr & ~__PERCPU_REF_ATOMIC_DEAD); + ref->percpu_count_ptr & ~__PERCPU_REF_ATOMIC); +} + +/** + * percpu_ref_switch_to_percpu - switch a percpu_ref to percpu mode + * @ref: percpu_ref to switch to percpu mode + * + * There's no reason to use this function for the usual reference counting. + * To re-use an expired ref, use percpu_ref_reinit(). + * + * Switch @ref to percpu mode. This function may be invoked concurrently + * with all the get/put operations and can safely be mixed with kill and + * reinit operations. + * + * This function normally doesn't block and can be called from any context + * but it may block if @ref is in the process of switching to atomic mode + * by percpu_ref_switch_atomic(). + */ +void percpu_ref_switch_to_percpu(struct percpu_ref *ref) +{ + /* a dying or dead ref can't be switched to percpu mode w/o reinit */ + if (!(ref->percpu_count_ptr & __PERCPU_REF_DEAD)) + __percpu_ref_switch_to_percpu(ref); } -EXPORT_SYMBOL_GPL(percpu_ref_reinit); /** * percpu_ref_kill_and_confirm - drop the initial ref and schedule confirmation @@ -253,8 +267,8 @@ EXPORT_SYMBOL_GPL(percpu_ref_reinit); * percpu_ref_tryget_live() for details. * * This function normally doesn't block and can be called from any context - * but it may block if @confirm_kill is specified and @ref is already in - * the process of switching to atomic mode by percpu_ref_switch_atomic(). + * but it may block if @confirm_kill is specified and @ref is in the + * process of switching to atomic mode by percpu_ref_switch_atomic(). * * Due to the way percpu_ref is implemented, @confirm_switch will be called * after at least one full sched RCU grace period has passed but this is an @@ -271,3 +285,24 @@ void percpu_ref_kill_and_confirm(struct percpu_ref *ref, percpu_ref_put(ref); } EXPORT_SYMBOL_GPL(percpu_ref_kill_and_confirm); + +/** + * 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 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) +{ + WARN_ON_ONCE(!percpu_ref_is_zero(ref)); + + ref->percpu_count_ptr &= ~__PERCPU_REF_DEAD; + percpu_ref_get(ref); + __percpu_ref_switch_to_percpu(ref); +} +EXPORT_SYMBOL_GPL(percpu_ref_reinit); |