From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759939Ab0FJXME (ORCPT ); Thu, 10 Jun 2010 19:12:04 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36374 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759880Ab0FJXL6 (ORCPT ); Thu, 10 Jun 2010 19:11:58 -0400 Date: Fri, 11 Jun 2010 01:10:18 +0200 From: Oleg Nesterov To: Ingo Molnar Cc: Peter Zijlstra , Stanislaw Gruszka , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: [PATCH 5/5] run_posix_cpu_timers: don't check ->exit_state, use lock_task_sighand() Message-ID: <20100610231018.GA25942@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org run_posix_cpu_timers() doesn't work if current has already passed exit_notify(). This was needed to prevent the races with do_wait(). Since ea6d290c ->signal is always valid and can't go away. We can remove the "tsk->exit_state == 0" in fastpath_timer_check() and convert run_posix_cpu_timers() to use lock_task_sighand(). Note: it makes sense to take group_leader's sighand instead, the sub-thread still uses CPU after release_task(). But we need more changes to do this. Signed-off-by: Oleg Nesterov --- kernel/posix-cpu-timers.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) --- 35-rc2/kernel/posix-cpu-timers.c~5_RUN_PCT_DONT_CK_EXIT_STATE 2010-06-11 01:07:48.000000000 +0200 +++ 35-rc2/kernel/posix-cpu-timers.c 2010-06-11 01:08:03.000000000 +0200 @@ -1272,10 +1272,6 @@ static inline int fastpath_timer_check(s { struct signal_struct *sig; - /* tsk == current, ensure it is safe to use ->signal/sighand */ - if (unlikely(tsk->exit_state)) - return 0; - if (!task_cputime_zero(&tsk->cputime_expires)) { struct task_cputime task_sample = { .utime = tsk->utime, @@ -1308,6 +1304,7 @@ void run_posix_cpu_timers(struct task_st { LIST_HEAD(firing); struct k_itimer *timer, *next; + unsigned long flags; BUG_ON(!irqs_disabled()); @@ -1318,7 +1315,8 @@ void run_posix_cpu_timers(struct task_st if (!fastpath_timer_check(tsk)) return; - spin_lock(&tsk->sighand->siglock); + if (!lock_task_sighand(tsk, &flags)) + return; /* * Here we take off tsk->signal->cpu_timers[N] and * tsk->cpu_timers[N] all the timers that are firing, and @@ -1340,7 +1338,7 @@ void run_posix_cpu_timers(struct task_st * that gets the timer lock before we do will give it up and * spin until we've taken care of that timer below. */ - spin_unlock(&tsk->sighand->siglock); + unlock_task_sighand(tsk, &flags); /* * Now that all the timers on our list have the firing flag,