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SubjectRe: utime/stime decreasing on thread exit
On 11/10, Stanislaw Gruszka wrote:
>
> 10 129 mm/oom_kill.c <<badness>>
> thread_group_cputime(p, &task_time);
>
> Not sure about 10 - oom killer.

Not sure too, but I don't think we should worry about badness().

> One other exception is:
> fastpath_timer_check() -> thread_group_cputimer() -> thread_group_cputime()
>
> We can solve this like that:
>
> --- a/kernel/posix-cpu-timers.c
> +++ b/kernel/posix-cpu-timers.c
> @@ -1375,13 +1375,8 @@ static inline int fastpath_timer_check(struct task_struct *tsk)
> }
>
> sig = tsk->signal;
> - if (!task_cputime_zero(&sig->cputime_expires)) {
> - struct task_cputime group_sample;
> -
> - thread_group_cputimer(tsk, &group_sample);
> - if (task_cputime_expired(&group_sample, &sig->cputime_expires))
> - return 1;
> - }
> + if (!task_cputime_zero(&sig->cputime_expires))
> + return 1;
>
> return sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY;
> }
>
> 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() ?
IOW, if sig->cputime_expires != 0 then ->running must be true.

At least, shouldn't stop_process_timers() clear sig->cputime_expires ?

Oleg.



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