From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935910AbcIFTCN (ORCPT ); Tue, 6 Sep 2016 15:02:13 -0400 Received: from merlin.infradead.org ([205.233.59.134]:40220 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935399AbcIFTBk (ORCPT ); Tue, 6 Sep 2016 15:01:40 -0400 Date: Tue, 6 Sep 2016 21:01:29 +0200 From: Peter Zijlstra To: Stanislaw Gruszka Cc: linux-kernel@vger.kernel.org, Giovanni Gherdovich , Linus Torvalds , Mel Gorman , Mike Galbraith , Paolo Bonzini , Rik van Riel , Thomas Gleixner , Wanpeng Li , Ingo Molnar Subject: Re: [PATCH v3] sched/cputime: Protect some other sum_exec_runtime reads on 32 bit cpus Message-ID: <20160906190129.GO10153@twins.programming.kicks-ass.net> References: <1473166148-8466-1-git-send-email-sgruszka@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1473166148-8466-1-git-send-email-sgruszka@redhat.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 06, 2016 at 02:49:08PM +0200, Stanislaw Gruszka wrote: > diff --git a/kernel/exit.c b/kernel/exit.c > index 2f974ae..a46f96f 100644 > --- a/kernel/exit.c > +++ b/kernel/exit.c > @@ -134,7 +134,7 @@ static void __exit_signal(struct task_struct *tsk) > sig->inblock += task_io_get_inblock(tsk); > sig->oublock += task_io_get_oublock(tsk); > task_io_accounting_add(&sig->ioac, &tsk->ioac); > - sig->sum_sched_runtime += tsk->se.sum_exec_runtime; > + sig->sum_sched_runtime += read_sum_exec_runtime(tsk); > sig->nr_threads--; > __unhash_process(tsk, group_dead); > write_sequnlock(&sig->stats_lock); If I'm not mistaken, at this point @p is dead, sum_exec_runtime will not ever be updated again. > diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c > index b93c72d..4d080f2 100644 > --- a/kernel/sched/cputime.c > +++ b/kernel/sched/cputime.c > @@ -702,7 +682,7 @@ out: > void task_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st) > { > struct task_cputime cputime = { > - .sum_exec_runtime = p->se.sum_exec_runtime, > + .sum_exec_runtime = read_sum_exec_runtime(p), > }; > > task_cputime(p, &cputime.utime, &cputime.stime); Right, even if @p == current, this can race with an interrupt (the tick) updating sum_exec_runtime. > diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c > index 39008d7..a2d753b 100644 > --- a/kernel/time/posix-cpu-timers.c > +++ b/kernel/time/posix-cpu-timers.c > @@ -848,7 +848,7 @@ static void check_thread_timers(struct task_struct *tsk, > tsk_expires->virt_exp = expires_to_cputime(expires); > > tsk_expires->sched_exp = check_timers_list(++timers, firing, > - tsk->se.sum_exec_runtime); > + read_sum_exec_runtime(tsk)); > > /* > * Check for the special case thread timers. @tsk == current and IRQs are disabled, sum_exec_runtime cannot be updated. > @@ -1115,7 +1115,7 @@ static inline int fastpath_timer_check(struct task_struct *tsk) > struct task_cputime task_sample; > > task_cputime(tsk, &task_sample.utime, &task_sample.stime); > - task_sample.sum_exec_runtime = tsk->se.sum_exec_runtime; > + task_sample.sum_exec_runtime = read_sum_exec_runtime(tsk); > if (task_cputime_expired(&task_sample, &tsk->cputime_expires)) > return 1; > } Same.