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Message-ID: <20230809192651.GU212435@hirez.programming.kicks-ass.net>
Date: Wed, 9 Aug 2023 21:26:51 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Valentin Schneider <vschneid@...hat.com>
Cc: mingo@...hat.com, juri.lelli@...hat.com,
vincent.guittot@...aro.org, dietmar.eggemann@....com,
rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
bristot@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/9] sched: Simplify ttwu()
On Wed, Aug 09, 2023 at 04:21:36PM +0100, Valentin Schneider wrote:
> On 01/08/23 22:41, Peter Zijlstra wrote:
> > Use guards to reduce gotos and simplify control flow.
> >
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > ---
> > kernel/sched/core.c | 221 +++++++++++++++++++++++++---------------------------
> > 1 file changed, 109 insertions(+), 112 deletions(-)
> >
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -3706,14 +3706,14 @@ ttwu_stat(struct task_struct *p, int cpu
> > struct sched_domain *sd;
> >
> > __schedstat_inc(p->stats.nr_wakeups_remote);
> > - rcu_read_lock();
> > +
> > + guard(rcu)();
>
> This isn't strictly equivalent, right? AFAICT that pushes the
> rcu_read_unlock() further down than it currently is - not a big deal, but
> indentation aside scoped_guard() would preserve that.
The full hunk:
| @@ -3706,14 +3706,14 @@ ttwu_stat(struct task_struct *p, int cpu
| struct sched_domain *sd;
|
| __schedstat_inc(p->stats.nr_wakeups_remote);
| - rcu_read_lock();
| +
| + guard(rcu)();
| for_each_domain(rq->cpu, sd) {
| if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
| __schedstat_inc(sd->ttwu_wake_remote);
| break;
| }
| }
| - rcu_read_unlock();
| }
And you'll see the guard goes out of scope here ^
Which is the exact place rcu_read_unlock() was at, no?
|
| if (wake_flags & WF_MIGRATED)
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