2020-01-29 18:21:41

by Davidlohr Bueso

Subject: [PATCH] bluetooth: optimize barrier usage for Rmw atomics

Use smp_mb__before_atomic() instead of smp_mb() and avoid the
unnecessary barrier for non LL/SC architectures, such as x86.

Signed-off-by: Davidlohr Bueso <[email protected]>
---
net/bluetooth/hidp/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
index bef84b95e2c4..3b4fa27a44e6 100644
--- a/net/bluetooth/hidp/core.c
+++ b/net/bluetooth/hidp/core.c
@@ -1279,7 +1279,7 @@ static int hidp_session_thread(void *arg)
add_wait_queue(sk_sleep(session->intr_sock->sk), &intr_wait);
/* This memory barrier is paired with wq_has_sleeper(). See
* sock_poll_wait() for more information why this is needed. */
- smp_mb();
+ smp_mb__before_atomic();

/* notify synchronous startup that we're ready */
atomic_inc(&session->state);
--
2.16.4

2020-01-29 19:03:53

by Marcel Holtmann

Subject: Re: [PATCH] bluetooth: optimize barrier usage for Rmw atomics

Hi Davidlohr,

> Use smp_mb__before_atomic() instead of smp_mb() and avoid the
> unnecessary barrier for non LL/SC architectures, such as x86.
>
> Signed-off-by: Davidlohr Bueso <[email protected]>
> ---
> net/bluetooth/hidp/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)

patch has been applied to bluetooth-next tree.

Regards

Marcel