Messages in this thread | | | Date | Tue, 20 Aug 2019 19:57:37 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [patch 04/44] posix-cpu-timers: Fixup stale comment |
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On Tue, 20 Aug 2019, Frederic Weisbecker wrote: > On Mon, Aug 19, 2019 at 04:31:45PM +0200, Thomas Gleixner wrote: > > /* > > - * Clean out CPU timers still ticking when a thread exited. The task > > - * pointer is cleared, and the expiry time is replaced with the residual > > - * time for later timer_gettime calls to return. > > + * Clean out CPU timers which are still armed when a thread exits. The > > + * timers are only removed from the list. No other updates are done. The > > + * corresponding posix timers are still accessible, but cannot be rearmed. > > + * > > * This must be called with the siglock held. > > */ > > static void cleanup_timers(struct list_head *head) > > Indeed and I believe we could avoid that step. We remove the sighand at the same > time so those can't be accessed anymore anyway. > > exit_itimers() takes care of the last call release and could force remove from > the list (although it might be taken care of in your series, haven't checked yet):
No. The posix timer is not necessarily owned by the exiting task or process. It can be owned by a different entity which has permissions, e.g. parent.
So those are not in the posix timer list of the exiting task, which gets cleaned up in exit_itimers(). Those are in the list of the task which armed the timer. The timer is merily queued in the 'active timers' list of the exiting task and posix_cpu_timers_exit()/posix_cpu_timers_exit_group() remove it before the task/signal structs go away.
Thanks,
tglx
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