From: Frederic Weisbecker <frederic@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
x86@kernel.org, Oleg Nesterov <oleg@redhat.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
John Stultz <john.stultz@linaro.org>,
Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [patch V2 3/5] posix-cpu-timers: Provide mechanisms to defer timer handling to task_work
Date: Thu, 23 Jul 2020 03:03:15 +0200 [thread overview]
Message-ID: <20200723010314.GA28401@lenoir> (raw)
In-Reply-To: <20200716225034.GK5523@worktop.programming.kicks-ass.net>
On Fri, Jul 17, 2020 at 12:50:34AM +0200, Peter Zijlstra wrote:
> On Thu, Jul 16, 2020 at 10:19:26PM +0200, Thomas Gleixner wrote:
> > +static void __run_posix_cpu_timers(struct task_struct *tsk)
> > +{
> > + struct posix_cputimers *pct = &tsk->posix_cputimers;
> > +
> > + if (!test_and_set_bit(CPUTIMERS_WORK_SCHEDULED, &pct->flags))
> > + task_work_add(tsk, &pct->task_work, true);
> > +}
> > +
> > +static inline void posix_cpu_timers_enable_work(struct task_struct *tsk)
> > +{
> > + clear_bit(CPUTIMERS_WORK_SCHEDULED, &tsk->posix_cputimers.flags);
> /*
> * Ensure we observe everything before a failing test_and_set()
> * in __run_posix_cpu_timers().
> */
> smp_mb__after_atomic();
> > +}
>
> Such that when another timer interrupt happens while we run this, we're
> guaranteed to either see it, or get re-queued and thus re-run the
> function.
But each thread in the process enqueues its own task work and flips its
own flags. So if task A runs the task work and task B runs __run_posix_cpu_timers(),
they wouldn't be ordering against the same flags.
next prev parent reply other threads:[~2020-07-23 1:03 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-16 20:19 [patch V2 0/5] posix-cpu-timers: Move expiry into task work context Thomas Gleixner
2020-07-16 20:19 ` [patch V2 1/5] posix-cpu-timers: Split run_posix_cpu_timers() Thomas Gleixner
2020-07-16 20:19 ` [patch V2 2/5] posix-cpu-timers: Convert the flags to a bitmap Thomas Gleixner
2020-07-21 12:34 ` Frederic Weisbecker
2020-07-21 16:10 ` Thomas Gleixner
2020-07-21 16:23 ` David Laight
2020-07-21 18:30 ` Thomas Gleixner
2020-07-16 20:19 ` [patch V2 3/5] posix-cpu-timers: Provide mechanisms to defer timer handling to task_work Thomas Gleixner
2020-07-16 22:50 ` Peter Zijlstra
2020-07-17 18:37 ` Thomas Gleixner
2020-07-23 1:03 ` Frederic Weisbecker [this message]
2020-07-23 8:32 ` Thomas Gleixner
2020-07-23 12:15 ` Frederic Weisbecker
2020-07-16 22:54 ` Peter Zijlstra
2020-07-17 18:38 ` Thomas Gleixner
2020-07-19 19:33 ` Thomas Gleixner
2020-07-21 18:50 ` Thomas Gleixner
2020-07-17 17:26 ` Oleg Nesterov
2020-07-17 18:35 ` Thomas Gleixner
2020-07-16 20:19 ` [patch V2 4/5] posix-cpu-timers: Expiry timers directly when in task work context Thomas Gleixner
2020-07-16 20:19 ` [patch V2 5/5] x86: Select POSIX_CPU_TIMERS_TASK_WORK Thomas Gleixner
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