From: Frederic Weisbecker <frederic@kernel.org>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Boqun Feng <boqun.feng@gmail.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Neeraj Upadhyay <neeraju@codeaurora.org>,
Josh Triplett <josh@joshtriplett.org>,
Stable <stable@vger.kernel.org>,
Joel Fernandes <joel@joelfernandes.org>
Subject: Re: [PATCH 10/13] rcu/nocb: Delete bypass_timer upon nocb_gp wakeup
Date: Wed, 10 Mar 2021 23:17:02 +0100 [thread overview]
Message-ID: <20210310221702.GC2949@lothringen> (raw)
In-Reply-To: <20210303012456.GC20917@paulmck-ThinkPad-P72>
On Tue, Mar 02, 2021 at 05:24:56PM -0800, Paul E. McKenney wrote:
> On Tue, Feb 23, 2021 at 01:10:08AM +0100, Frederic Weisbecker wrote:
> > A NOCB-gp wake up can safely delete the nocb_bypass_timer. nocb_gp_wait()
> > is going to check again the bypass state and rearm the bypass timer if
> > necessary.
> >
> > Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
> > Cc: Josh Triplett <josh@joshtriplett.org>
> > Cc: Lai Jiangshan <jiangshanlai@gmail.com>
> > Cc: Joel Fernandes <joel@joelfernandes.org>
> > Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
> > Cc: Boqun Feng <boqun.feng@gmail.com>
>
> Give that you delete this code a couple of patches later in this series,
> why not just leave it out entirely? ;-)
It's not exactly deleted later, it's rather merged within the
"del_timer(&rdp_gp->nocb_timer)".
The purpose of that patch is to make it clear that we explicitly cancel
the nocb_bypass_timer here before we do it implicitly later with the
merge of nocb_bypass_timer into nocb_timer.
We could drop that patch, the resulting code in the end of the patchset
will be the same of course but the behaviour detail described here might
slip out of the reviewers attention :-)
>
> Thanx, Paul
>
> > ---
> > kernel/rcu/tree_plugin.h | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> > index b62ad79bbda5..9da67b0d3997 100644
> > --- a/kernel/rcu/tree_plugin.h
> > +++ b/kernel/rcu/tree_plugin.h
> > @@ -1711,6 +1711,8 @@ static bool __wake_nocb_gp(struct rcu_data *rdp_gp,
> > del_timer(&rdp_gp->nocb_timer);
> > }
> >
> > + del_timer(&rdp_gp->nocb_bypass_timer);
> > +
> > if (force || READ_ONCE(rdp_gp->nocb_gp_sleep)) {
> > WRITE_ONCE(rdp_gp->nocb_gp_sleep, false);
> > needwake = true;
Thanks.
next prev parent reply other threads:[~2021-03-10 22:17 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-23 0:09 [PATCH 00/13] rcu/nocb updates v2 Frederic Weisbecker
2021-02-23 0:09 ` [PATCH 01/13] rcu/nocb: Fix potential missed nocb_timer rearm Frederic Weisbecker
2021-02-24 18:37 ` Paul E. McKenney
2021-02-24 22:06 ` Frederic Weisbecker
2021-02-25 0:14 ` Paul E. McKenney
2021-02-25 0:48 ` Frederic Weisbecker
2021-02-25 1:07 ` Paul E. McKenney
2021-03-02 1:48 ` Paul E. McKenney
2021-03-02 12:34 ` Frederic Weisbecker
2021-03-02 18:17 ` Paul E. McKenney
2021-03-03 1:35 ` Frederic Weisbecker
2021-03-03 2:06 ` Paul E. McKenney
2021-03-03 2:17 ` Frederic Weisbecker
2021-03-03 11:15 ` Neeraj Upadhyay
2021-02-23 0:10 ` [PATCH 02/13] rcu/nocb: Disable bypass when CPU isn't completely offloaded Frederic Weisbecker
2021-02-23 0:10 ` [PATCH 03/13] rcu/nocb: Remove stale comment above rcu_segcblist_offload() Frederic Weisbecker
2021-02-23 0:10 ` [PATCH 04/13] rcu/nocb: Move trace_rcu_nocb_wake() calls outside nocb_lock when possible Frederic Weisbecker
2021-02-23 0:10 ` [PATCH 05/13] rcu/nocb: Merge nocb_timer to the rdp leader Frederic Weisbecker
2021-03-03 1:15 ` [PATCH 05/13] rcu/nocb: Use the rcuog CPU's ->nocb_timer Paul E. McKenney
2021-03-10 22:05 ` Frederic Weisbecker
2021-03-16 0:02 ` Paul E. McKenney
2021-02-23 0:10 ` [PATCH 06/13] timer: Revert "timer: Add timer_curr_running()" Frederic Weisbecker
2021-02-23 0:10 ` [PATCH 07/13] rcu/nocb: Directly call __wake_nocb_gp() from bypass timer Frederic Weisbecker
2021-02-23 0:10 ` [PATCH 08/13] rcu/nocb: Allow de-offloading rdp leader Frederic Weisbecker
2021-02-23 0:10 ` [PATCH 09/13] rcu/nocb: Cancel nocb_timer upon nocb_gp wakeup Frederic Weisbecker
2021-02-23 0:10 ` [PATCH 10/13] rcu/nocb: Delete bypass_timer " Frederic Weisbecker
2021-03-03 1:24 ` Paul E. McKenney
2021-03-10 22:17 ` Frederic Weisbecker [this message]
2021-03-15 14:53 ` Boqun Feng
2021-03-15 22:56 ` Frederic Weisbecker
2021-03-16 0:02 ` Paul E. McKenney
2021-02-23 0:10 ` [PATCH 11/13] rcu/nocb: Only cancel nocb timer if not polling Frederic Weisbecker
2021-03-03 1:22 ` Paul E. McKenney
2021-03-10 22:08 ` Frederic Weisbecker
2021-02-23 0:10 ` [PATCH 12/13] rcu/nocb: Prepare for finegrained deferred wakeup Frederic Weisbecker
2021-03-16 3:02 ` Paul E. McKenney
2021-03-16 11:45 ` Frederic Weisbecker
2021-03-16 14:02 ` Paul E. McKenney
2021-02-23 0:10 ` [PATCH 13/13] rcu/nocb: Unify timers Frederic Weisbecker
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