From: Thomas Gleixner <tglx@linutronix.de>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Oleg Nesterov <oleg@redhat.com>, Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
John Stultz <john.stultz@linaro.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Anna-Maria Behnsen <anna-maria@linutronix.de>
Subject: Re: [patch 04/44] posix-cpu-timers: Fixup stale comment
Date: Tue, 20 Aug 2019 19:57:37 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.21.1908201946320.2223@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20190820142658.GG2093@lenoir>
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
next prev parent reply other threads:[~2019-08-20 17:57 UTC|newest]
Thread overview: 83+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-19 14:31 [patch 00/44] posix-cpu-timers: Cleanup and consolidation Thomas Gleixner
2019-08-19 14:31 ` [patch 01/44] posix-timers: Cleanup forward declarations and includes Thomas Gleixner
2019-08-20 12:20 ` Frederic Weisbecker
2019-08-20 13:03 ` Thomas Gleixner
2019-08-20 13:48 ` Frederic Weisbecker
2019-08-23 2:12 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-19 14:31 ` [patch 02/44] alarmtimers: Avoid rtc.h include Thomas Gleixner
2019-08-20 13:49 ` Frederic Weisbecker
2019-08-23 2:12 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-19 14:31 ` [patch 03/44] posix-timer: Use a callback for cancel synchronization Thomas Gleixner
2019-08-20 2:21 ` Christoph Hellwig
2019-08-20 13:08 ` Thomas Gleixner
2019-08-20 13:59 ` Frederic Weisbecker
2019-08-23 2:12 ` [tip: timers/core] posix-timers: Use a callback for cancel synchronization on PREEMPT_RT tip-bot2 for Thomas Gleixner
2019-08-19 14:31 ` [patch 04/44] posix-cpu-timers: Fixup stale comment Thomas Gleixner
2019-08-20 14:26 ` Frederic Weisbecker
2019-08-20 17:57 ` Thomas Gleixner [this message]
2019-08-20 20:48 ` Frederic Weisbecker
2019-08-20 21:43 ` Thomas Gleixner
2019-08-20 22:56 ` Frederic Weisbecker
2019-08-21 13:31 ` Thomas Gleixner
2019-08-21 15:51 ` Frederic Weisbecker
2019-08-23 2:12 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-19 14:31 ` [patch 05/44] posix-cpu-timers: Sanitize bogus WARNONS Thomas Gleixner
2019-08-21 11:34 ` Frederic Weisbecker
2019-08-23 2:12 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-19 14:31 ` [patch 06/44] posix-cpu-timers: Remove tsk argument from run_posix_cpu_timers() Thomas Gleixner
2019-08-21 11:36 ` Frederic Weisbecker
2019-08-23 2:12 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-19 14:31 ` [patch 07/44] posix-cpu-timers: Simplify sighand locking in run_posix_cpu_timers() Thomas Gleixner
2019-08-21 12:09 ` Frederic Weisbecker
2019-08-21 13:25 ` Thomas Gleixner
2019-08-21 15:42 ` Frederic Weisbecker
2019-08-21 17:13 ` Thomas Gleixner
2019-08-19 14:31 ` [patch 08/44] posix-cpu-timers: Provide task validation functions Thomas Gleixner
2019-08-19 14:31 ` [patch 09/44] posix-cpu-timers: Use common permission check in posix_cpu_clock_get() Thomas Gleixner
2019-08-19 14:31 ` [patch 10/44] posix-cpu-timers: Use common permission check in posix_cpu_timer_create() Thomas Gleixner
2019-08-19 14:31 ` [patch 11/44] posix-cpu-timers: Provide quick sample function for itimer Thomas Gleixner
2019-08-19 14:31 ` [patch 12/44] itimers: Use quick sample function Thomas Gleixner
2019-08-19 14:31 ` [patch 13/44] posix-cpu-timers: Sample directly in timer check Thomas Gleixner
2019-08-19 14:31 ` [patch 14/44] posix-cpu-timers: Rename thread_group_cputimer() and make it static Thomas Gleixner
2019-08-19 14:31 ` [patch 15/44] posix-cpu-timer: Comsolidate thread group sample code Thomas Gleixner
2019-08-19 19:07 ` Ingo Molnar
2019-08-19 14:31 ` [patch 16/44] posix-cpu-timers: Use clock ID in posix_cpu_timer_set() Thomas Gleixner
2019-08-19 14:31 ` [patch 17/44] posix-cpu-timers: Use clock ID in posix_cpu_timer_get() Thomas Gleixner
2019-08-19 14:31 ` [patch 18/44] posix-cpu-timers: Use clock ID in posix_cpu_timer_rearm() Thomas Gleixner
2019-08-19 14:32 ` [patch 19/44] posix-cpu-timer: Remove pointless return value check Thomas Gleixner
2019-08-19 14:32 ` [patch 20/44] posix-cpu-timers: Simplify sample functions Thomas Gleixner
2019-08-19 14:32 ` [patch 21/44] posix-cpu-timers: Get rid of pointer indirection Thomas Gleixner
2019-08-19 14:32 ` [patch 22/44] posix-cpu-timers: Sample task times once in expiry check Thomas Gleixner
2019-08-19 14:32 ` [patch 23/44] posix-cpu-timers: Move prof/virt_ticks into caller Thomas Gleixner
2019-08-19 14:32 ` [patch 24/44] posix-cpu-timers: Create a container struct Thomas Gleixner
2019-08-19 14:32 ` [patch 25/44] sched: Move struct task_cputime to types.h Thomas Gleixner
2019-08-19 14:32 ` [patch 26/44] posix-cpu-timers: Move expiry cache into struct posix_cputimers Thomas Gleixner
2019-08-19 14:32 ` [patch 27/44] posix-cpu-timers: Provide array based access to expiry cache Thomas Gleixner
2019-08-19 19:32 ` Ingo Molnar
2019-08-20 20:22 ` Thomas Gleixner
2019-08-19 14:32 ` [patch 28/44] posix-cpu-timers: Simplify timer queueing Thomas Gleixner
2019-08-19 14:32 ` [patch 29/44] posix-cpu-timers: Simplify set_process_cpu_timer() Thomas Gleixner
2019-08-19 14:32 ` [patch 30/44] posix-cpu-timers: Switch check_*_timers() to array cache Thomas Gleixner
2019-08-19 14:32 ` [patch 31/44] posix-cpu-timers: Remove the odd field rename defines Thomas Gleixner
2019-08-19 14:32 ` [patch 32/44] posix-cpu-timers: Provide array based sample functions Thomas Gleixner
2019-08-19 14:32 ` [patch 33/44] posix-cpu-timers: Make expiry checks array based Thomas Gleixner
2019-08-19 14:32 ` [patch 34/44] posix-cpu-timers: Remove cputime_expires Thomas Gleixner
2019-08-19 14:32 ` [patch 35/44] posix-cpu-timers: Switch thread group sampling to array Thomas Gleixner
2019-08-19 14:32 ` [patch 36/44] posix-cpu-timers: Get rid of zero checks Thomas Gleixner
2019-08-19 14:32 ` [patch 37/44] posix-cpu-timers: Consolidate timer expiry further Thomas Gleixner
2019-08-19 14:32 ` [patch 38/44] posix-cpu-timers: Respect INFINITY for hard RTTIME limit Thomas Gleixner
2019-08-19 20:06 ` Ingo Molnar
2019-08-19 20:29 ` Thomas Gleixner
2019-08-19 14:32 ` [patch 39/44] posix-cpu-timers: Get rid of 64bit divisions Thomas Gleixner
2019-08-19 14:32 ` [patch 40/44] posix-cpu-timers: Remove pointless comparisions Thomas Gleixner
2019-08-19 20:10 ` Ingo Molnar
2019-08-19 14:32 ` [patch 41/44] posix-cpu-timers: Deduplicate rlimit handling Thomas Gleixner
2019-08-19 14:32 ` [patch 42/44] posix-cpu-timers: Move state tracking to struct posix_cputimers Thomas Gleixner
2019-08-19 19:13 ` Ingo Molnar
2019-08-19 20:29 ` Thomas Gleixner
2019-08-19 14:32 ` [patch 43/44] posix-cpu-timers: Utilize timerqueue for storage Thomas Gleixner
2019-08-19 14:32 ` [patch 44/44] posix-cpu-timers: Expire timers directly Thomas Gleixner
2019-08-19 19:09 ` Ingo Molnar
2019-08-20 13:07 ` Thomas Gleixner
2019-08-20 2:18 ` [patch 00/44] posix-cpu-timers: Cleanup and consolidation Christoph Hellwig
2019-08-20 13:09 ` Thomas Gleixner
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