Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [patch V2 3/5] posix-cpu-timers: Provide mechanisms to defer timer handling to task_work | Date | Fri, 17 Jul 2020 20:37:51 +0200 |
| |
Peter Zijlstra <peterz@infradead.org> writes: > On Thu, Jul 16, 2020 at 10:19:26PM +0200, Thomas Gleixner wrote: > >> @@ -1096,6 +1099,12 @@ static void __run_posix_cpu_timers(struc >> check_process_timers(tsk, &firing); >> >> /* >> + * Allow new work to be scheduled. The expiry cache >> + * is up to date. >> + */ >> + posix_cpu_timers_enable_work(tsk); >> + >> + /* >> * We must release these locks before taking any timer's lock. >> * There is a potential race with timer deletion here, as the >> * siglock now protects our private firing list. We have set > > I think I would feel more comfortable if this was done at the very > beginning of that function, possibly even with: > >> +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.
Makes sense.
Thanks,
tglx
| |