Messages in this thread | | | Date | Tue, 10 Nov 2009 20:23:27 +0100 | From | Oleg Nesterov <> | Subject | Re: utime/stime decreasing on thread exit |
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On 11/10, Stanislaw Gruszka wrote: > > On Tue, Nov 10, 2009 at 06:40:08PM +0100, Oleg Nesterov wrote: > > > > > > Or stay with task_cputime_expired() but only if cputimer is currently running. > > > > Oh. I forgot this code completely, can't comment. > > > > Can't we ensure that fastpath_timer_check() never do while_each_thread() ? > > Removing possibility to call while_each_tread() from fastpath_timer_check() > was exactly my intension here, perhaps I was not clear.
Yes, yes, I understand.
I meant, perhaps we can ensure this shouldn't happen "by design", instead of checking ->running in fastpath_timer_check().
> > IOW, if sig->cputime_expires != 0 then ->running must be true. > > At least, shouldn't stop_process_timers() clear sig->cputime_expires ? > > I'm going to think about that. However as far seems, checking ->running > explicitly and goto slow patch when is not true is safer solution.
Yes, agreed.
Still. check_process_timers() updates sig->cputime_expires at the end, but it never clears it. For example,
if (sched_expires != 0 && (sig->cputime_expires.sched_exp == 0 || sig->cputime_expires.sched_exp > sched_expires)) sig->cputime_expires.sched_exp = sched_expires;
Why?
Now suppose that (say) sig->cputime_expires.sched_exp != 0, there are no cpu timers, ->running == F.
In this case fastpath_timer_check() always returns T and triggers the slow path which does nothing, not good.
But yes, I agree, probably we should start with the simple/safe change as you suggested.
Oleg.
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