Return-Path: From: Andrea Parri To: Marcel Holtmann , Johan Hedberg , "David S . Miller" Cc: linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Jeffy Chen , Brian Norris , AL Yu-Chen Cho , Andrea Parri Subject: [PATCH] bluetooth/{bnep,cmtp,hidp}: Remove unnecessary smp_mb__{before,after}_atomic Date: Tue, 14 Aug 2018 20:41:06 +0200 Message-Id: <1534272066-9366-1-git-send-email-andrea.parri@amarulasolutions.com> List-ID: The barriers are unneeded; wait_woken() and woken_wake_function() already provide us with the required synchronization: remove them and document that we're relying on the (implicit) synchronization provided by wait_woken() and woken_wake_function(). Signed-off-by: Andrea Parri --- net/bluetooth/bnep/core.c | 7 ++++--- net/bluetooth/cmtp/core.c | 14 ++++++++------ net/bluetooth/hidp/core.c | 13 ++++++++----- 3 files changed, 20 insertions(+), 14 deletions(-) diff --git a/net/bluetooth/bnep/core.c b/net/bluetooth/bnep/core.c index 7b3965861013c..43c284158f63e 100644 --- a/net/bluetooth/bnep/core.c +++ b/net/bluetooth/bnep/core.c @@ -489,9 +489,6 @@ static int bnep_session(void *arg) add_wait_queue(sk_sleep(sk), &wait); while (1) { - /* Ensure session->terminate is updated */ - smp_mb__before_atomic(); - if (atomic_read(&s->terminate)) break; /* RX */ @@ -512,6 +509,10 @@ static int bnep_session(void *arg) break; netif_wake_queue(dev); + /* + * wait_woken() performs the necessary memory barriers + * for us; see the header comment for this primitive. + */ wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT); } remove_wait_queue(sk_sleep(sk), &wait); diff --git a/net/bluetooth/cmtp/core.c b/net/bluetooth/cmtp/core.c index 7f26a5a19ff6d..07cfa3249f83a 100644 --- a/net/bluetooth/cmtp/core.c +++ b/net/bluetooth/cmtp/core.c @@ -288,9 +288,6 @@ static int cmtp_session(void *arg) add_wait_queue(sk_sleep(sk), &wait); while (1) { - /* Ensure session->terminate is updated */ - smp_mb__before_atomic(); - if (atomic_read(&session->terminate)) break; if (sk->sk_state != BT_CONNECTED) @@ -306,6 +303,10 @@ static int cmtp_session(void *arg) cmtp_process_transmit(session); + /* + * wait_woken() performs the necessary memory barriers + * for us; see the header comment for this primitive. + */ wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT); } remove_wait_queue(sk_sleep(sk), &wait); @@ -431,9 +432,10 @@ int cmtp_del_connection(struct cmtp_conndel_req *req) /* Stop session thread */ atomic_inc(&session->terminate); - /* Ensure session->terminate is updated */ - smp_mb__after_atomic(); - + /* + * See the comment preceding the call to wait_woken() + * in cmtp_session(). + */ wake_up_interruptible(sk_sleep(session->sock->sk)); } else err = -ENOENT; diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c index 1036e4fa1ea28..e621551712f59 100644 --- a/net/bluetooth/hidp/core.c +++ b/net/bluetooth/hidp/core.c @@ -1074,6 +1074,10 @@ static int hidp_session_start_sync(struct hidp_session *session) static void hidp_session_terminate(struct hidp_session *session) { atomic_inc(&session->terminate); + /* + * See the comment preceding the call to wait_woken() + * in hidp_session_run(). + */ wake_up_interruptible(&hidp_session_wq); } @@ -1193,8 +1197,6 @@ static void hidp_session_run(struct hidp_session *session) * thread is woken up by ->sk_state_changed(). */ - /* Ensure session->terminate is updated */ - smp_mb__before_atomic(); if (atomic_read(&session->terminate)) break; @@ -1228,14 +1230,15 @@ static void hidp_session_run(struct hidp_session *session) hidp_process_transmit(session, &session->ctrl_transmit, session->ctrl_sock); + /* + * wait_woken() performs the necessary memory barriers + * for us; see the header comment for this primitive. + */ wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT); } remove_wait_queue(&hidp_session_wq, &wait); atomic_inc(&session->terminate); - - /* Ensure session->terminate is updated */ - smp_mb__after_atomic(); } static int hidp_session_wake_function(wait_queue_entry_t *wait, -- 2.7.4