Messages in this thread Patch in this message | | | From | "Paul E. McKenney" <> | Subject | [PATCH rcu 08/14] percpu-refcount: Use call_rcu_flush() for atomic switch | Date | Wed, 19 Oct 2022 15:51:38 -0700 |
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From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
call_rcu() changes to save power will slow down the percpu refcounter's "per-CPU to atomic switch" path. The primitive uses RCU when switching to atomic mode. The enqueued async callback wakes up waiters waiting in the percpu_ref_switch_waitq. Due to this, per-CPU refcount users will slow down, such as blk_pre_runtime_suspend().
Use the call_rcu_flush() API instead which reverts to the old behavior.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> --- lib/percpu-refcount.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c index e5c5315da2741..65c58a029297d 100644 --- a/lib/percpu-refcount.c +++ b/lib/percpu-refcount.c @@ -230,7 +230,8 @@ static void __percpu_ref_switch_to_atomic(struct percpu_ref *ref, percpu_ref_noop_confirm_switch; percpu_ref_get(ref); /* put after confirmation */ - call_rcu(&ref->data->rcu, percpu_ref_switch_to_atomic_rcu); + call_rcu_flush(&ref->data->rcu, + percpu_ref_switch_to_atomic_rcu); } static void __percpu_ref_switch_to_percpu(struct percpu_ref *ref) -- 2.31.1.189.g2e36527f23
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