From: "Paul E. McKenney" <paulmck@kernel.org>
To: Liu Song <fishland@aliyun.com>
Cc: liu.song11@zte.com.cn, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] rcu: Remove unnecessary updates to ret in rcu_gp_fqs_loop
Date: Tue, 29 Jun 2021 10:44:08 -0700 [thread overview]
Message-ID: <20210629174408.GS4397@paulmck-ThinkPad-P17-Gen-1> (raw)
In-Reply-To: <20210629135551.4080-1-fishland@aliyun.com>
On Tue, Jun 29, 2021 at 09:55:51PM +0800, Liu Song wrote:
> From: Liu Song <liu.song11@zte.com.cn>
>
> The ret value will be updated in the subsequent process,
> so there is no need to update it here.
>
> Signed-off-by: Liu Song <liu.song11@zte.com.cn>
Good eyes, and it is safe to say that rcutorture would never have found
that one. ;-)
As usual, I could not resist the urge to edit the commit log, and I also
added the "(void)" to indicate that the code intends to ignore the return
value, as it now uses elapsed time to make its decisions.
Please let me know if I messed anything up.
Thanx, Paul
------------------------------------------------------------------------
commit 48434fc6700c31bd258713c24b78053fe47d393e
Author: Liu Song <liu.song11@zte.com.cn>
Date: Tue Jun 29 21:55:51 2021 +0800
rcu: Remove useless "ret" update in rcu_gp_fqs_loop()
Within rcu_gp_fqs_loop(), the "ret" local variable is set to the
return value from swait_event_idle_timeout_exclusive(), but "ret" is
unconditionally overwritten later in the code. This commit therefore
removes this useless assignment.
Signed-off-by: Liu Song <liu.song11@zte.com.cn>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 35ed10bb95ef..a627a200a5ae 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1958,8 +1958,8 @@ static noinline_for_stack void rcu_gp_fqs_loop(void)
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
TPS("fqswait"));
WRITE_ONCE(rcu_state.gp_state, RCU_GP_WAIT_FQS);
- ret = swait_event_idle_timeout_exclusive(
- rcu_state.gp_wq, rcu_gp_fqs_check_wake(&gf), j);
+ (void)swait_event_idle_timeout_exclusive(rcu_state.gp_wq,
+ rcu_gp_fqs_check_wake(&gf), j);
rcu_gp_torture_wait();
WRITE_ONCE(rcu_state.gp_state, RCU_GP_DOING_FQS);
/* Locking provides needed memory barriers. */
next parent reply other threads:[~2021-06-29 17:44 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210629135551.4080-1-fishland@aliyun.com>
2021-06-29 17:44 ` Paul E. McKenney [this message]
[not found] ` <202106301122531910761@zte.com.cn>
2021-06-30 4:23 ` [PATCH] rcu: Remove unnecessary updates to ret in rcu_gp_fqs_loop Paul E. McKenney
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