On Sat, 2014-08-16 at 19:50 +0200, Oleg Nesterov wrote:
> On 08/16, Rik van Riel wrote:
> >
> > + do {
> > + seq = nextseq;
> > + read_seqbegin_or_lock(&sig->stats_lock, &seq);
> > + times->utime = sig->utime;
> > + times->stime = sig->stime;
> > + times->sum_exec_runtime = sig->sum_sched_runtime;
> > +
> > + for_each_thread(tsk, t) {
> > + task_cputime(t, &utime, &stime);
> > + times->utime += utime;
> > + times->stime += stime;
> > + times->sum_exec_runtime += task_sched_runtime(t);
> > + }
> > + /* If lockless access failed, take the lock. */
> > + nextseq = 1;
>
> Yes, thanks, this answers my concerns.
>
> Cough... can't resist, and I still think that we should take rcu_read_lock()
> only around for_each_thread() and the patch expands the critical section for
> no reason. But this is minor, I won't insist.
Hm. Should traversal not also disable preemption to preserve the error
bound Peter mentioned?
-Mike
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