From 3b13c168186c115501ee7d194460ba2f8c825155 Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Thu, 21 Oct 2021 14:30:51 +0100 Subject: [PATCH] percpu_ref: percpu_ref_tryget_live() version holding RCU Add percpu_ref_tryget_live_rcu(), which is a version of percpu_ref_tryget_live() but the user is responsible for enclosing it in a RCU read lock section. Signed-off-by: Pavel Begunkov Acked-by: Dennis Zhou Link: https://lore.kernel.org/r/3066500d7a6eb3e03f10adf98b87fdb3b1c49db8.1634822969.git.asml.silence@gmail.com Signed-off-by: Jens Axboe --- include/linux/percpu-refcount.h | 33 +++++++++++++++++++++++---------- 1 file changed, 23 insertions(+), 10 deletions(-) diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h index ae16a9856305..b31d3f3312ce 100644 --- a/include/linux/percpu-refcount.h +++ b/include/linux/percpu-refcount.h @@ -266,6 +266,28 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref) return percpu_ref_tryget_many(ref, 1); } +/** + * percpu_ref_tryget_live_rcu - same as percpu_ref_tryget_live() but the + * caller is responsible for taking RCU. + * + * This function is safe to call as long as @ref is between init and exit. + */ +static inline bool percpu_ref_tryget_live_rcu(struct percpu_ref *ref) +{ + unsigned long __percpu *percpu_count; + bool ret = false; + + WARN_ON_ONCE(!rcu_read_lock_held()); + + if (likely(__ref_is_percpu(ref, &percpu_count))) { + this_cpu_inc(*percpu_count); + ret = true; + } else if (!(ref->percpu_count_ptr & __PERCPU_REF_DEAD)) { + ret = atomic_long_inc_not_zero(&ref->data->count); + } + return ret; +} + /** * percpu_ref_tryget_live - try to increment a live percpu refcount * @ref: percpu_ref to try-get @@ -283,20 +305,11 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref) */ static inline bool percpu_ref_tryget_live(struct percpu_ref *ref) { - unsigned long __percpu *percpu_count; bool ret = false; rcu_read_lock(); - - if (__ref_is_percpu(ref, &percpu_count)) { - this_cpu_inc(*percpu_count); - ret = true; - } else if (!(ref->percpu_count_ptr & __PERCPU_REF_DEAD)) { - ret = atomic_long_inc_not_zero(&ref->data->count); - } - + ret = percpu_ref_tryget_live_rcu(ref); rcu_read_unlock(); - return ret; }