Messages in this thread | | | Date | Thu, 23 Jul 2020 03:03:15 +0200 | From | Frederic Weisbecker <> | Subject | Re: [patch V2 3/5] posix-cpu-timers: Provide mechanisms to defer timer handling to task_work |
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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.
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