From: "Paul E. McKenney" <paulmck@kernel.org>
To: Lai Jiangshan <laijs@linux.alibaba.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Josh Triplett <josh@joshtriplett.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
rcu@vger.kernel.org
Subject: Re: [PATCH V2 3/7] rcu: remove useless special.b.deferred_qs
Date: Mon, 17 Feb 2020 15:23:53 -0800 [thread overview]
Message-ID: <20200217232353.GB17570@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20191102124559.1135-4-laijs@linux.alibaba.com>
On Sat, Nov 02, 2019 at 12:45:55PM +0000, Lai Jiangshan wrote:
> ->read_read_unlock_special.b.deferred_qs is set when
> ->read_read_unlock_special is non-zero, and it is cleared when
> ->read_read_unlock_special is cleared.
>
> So it is useless.
>
> Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
I have queued this on -rcu for further review and testing, thank you!
Thanx, Paul
> ---
> include/linux/sched.h | 2 +-
> kernel/rcu/tree_plugin.h | 1 -
> 2 files changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 2c2e56bd8913..3ba392d71de9 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -604,7 +604,7 @@ union rcu_special {
> u8 blocked;
> u8 need_qs;
> u8 exp_hint; /* Hint for performance. */
> - u8 deferred_qs;
> + u8 pad; /* No garbage from compiler! */
> } b; /* Bits. */
> u32 s; /* Set of bits. */
> };
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index 2fab8be2061f..f2fd7d687bdb 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -622,7 +622,6 @@ static void rcu_read_unlock_special(struct task_struct *t)
> irq_work_queue_on(&rdp->defer_qs_iw, rdp->cpu);
> }
> }
> - t->rcu_read_unlock_special.b.deferred_qs = true;
> local_irq_restore(flags);
> return;
> }
> --
> 2.20.1
>
next prev parent reply other threads:[~2020-02-17 23:23 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-02 12:45 [PATCH V2 0/7] rcu: introduce percpu rcu_preempt_depth Lai Jiangshan
2019-11-02 12:45 ` [PATCH V2 1/7] rcu: use preempt_count to test whether scheduler locks is held Lai Jiangshan
2019-11-15 16:53 ` Paul E. McKenney
2020-02-19 3:31 ` Joel Fernandes
2020-02-19 3:59 ` Paul E. McKenney
2019-11-02 12:45 ` [PATCH V2 2/7] rcu: cleanup rcu_preempt_deferred_qs() Lai Jiangshan
2019-11-03 2:01 ` Boqun Feng
2019-11-03 5:01 ` Lai Jiangshan
2019-11-04 14:55 ` Paul E. McKenney
2019-11-05 2:09 ` Lai Jiangshan
2019-11-05 7:19 ` Paul E. McKenney
2019-11-11 14:32 ` Paul E. McKenney
2019-11-12 1:28 ` Lai Jiangshan
2020-02-17 23:23 ` Paul E. McKenney
2020-02-18 14:41 ` Steven Rostedt
2020-02-18 16:43 ` Paul E. McKenney
2019-11-15 16:55 ` Paul E. McKenney
2019-11-02 12:45 ` [PATCH V2 3/7] rcu: remove useless special.b.deferred_qs Lai Jiangshan
2020-02-17 23:23 ` Paul E. McKenney [this message]
2019-11-02 12:45 ` [PATCH V2 4/7] rcu: don't use negative ->rcu_read_lock_nesting Lai Jiangshan
2020-02-17 23:26 ` Paul E. McKenney
2019-11-02 12:45 ` [PATCH V2 5/7] rcu: wrap usages of rcu_read_lock_nesting Lai Jiangshan
2019-11-15 22:25 ` Paul E. McKenney
2019-11-02 12:45 ` [PATCH V2 6/7] rcu: clear the special.b.need_qs in rcu_note_context_switch() Lai Jiangshan
2019-11-16 15:46 ` Paul E. McKenney
2019-11-02 12:45 ` [PATCH V2 7/7] x86,rcu: use percpu rcu_preempt_depth Lai Jiangshan
2019-11-02 16:30 ` Borislav Petkov
2019-11-03 4:33 ` Lai Jiangshan
2019-11-04 9:25 ` Sebastian Andrzej Siewior
2019-11-04 11:41 ` Lai Jiangshan
2019-11-04 12:09 ` Sebastian Andrzej Siewior
2019-11-16 15:48 ` Paul E. McKenney
2019-11-18 2:02 ` Lai Jiangshan
2019-11-18 14:59 ` Paul E. McKenney
2019-11-19 1:59 ` Lai Jiangshan
2019-11-19 21:14 ` Paul E. McKenney
2019-11-20 2:47 ` Lai Jiangshan
2019-11-21 4:02 ` Paul E. McKenney
2019-11-02 15:05 ` [PATCH V2 0/7] rcu: introduce " Paul E. McKenney
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