From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751856Ab0ATMil (ORCPT ); Wed, 20 Jan 2010 07:38:41 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752332Ab0ATMiE (ORCPT ); Wed, 20 Jan 2010 07:38:04 -0500 Received: from mx1.redhat.com ([209.132.183.28]:61914 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932099Ab0ATMh7 (ORCPT ); Wed, 20 Jan 2010 07:37:59 -0500 From: Stanislaw Gruszka To: Thomas Gleixner , Andrew Morton Cc: Ingo Molnar , Oleg Nesterov , Peter Zijlstra , Hidetoshi Seto , Balbir Singh , linux-kernel@vger.kernel.org, Stanislaw Gruszka Subject: [PATCH 5/6 -mm] cpu-timers: assure to not iterate over all threads in fastpath_timer_check() Date: Wed, 20 Jan 2010 13:34:27 +0100 Message-Id: <1263990868-8119-6-git-send-email-sgruszka@redhat.com> In-Reply-To: <1263990868-8119-5-git-send-email-sgruszka@redhat.com> References: <1263990868-8119-1-git-send-email-sgruszka@redhat.com> <1263990868-8119-2-git-send-email-sgruszka@redhat.com> <1263990868-8119-3-git-send-email-sgruszka@redhat.com> <1263990868-8119-4-git-send-email-sgruszka@redhat.com> <1263990868-8119-5-git-send-email-sgruszka@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Spread p->sighand->siglock locking scope to assure fastpath_timer_check() never iterate over each threads. Without locking there is small possibility that signal->cputimer will stop running while we write values to signal->cputime_expires. Calling thread_group_cputime() from fastpath_timer_check() is not only bad because it is slow, also it is racy with __exit_signal() which can lead to invalid signal->{s,u}time values. Signed-off-by: Stanislaw Gruszka --- kernel/posix-cpu-timers.c | 14 +++++++------- 1 files changed, 7 insertions(+), 7 deletions(-) diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c index faa0b42..67c877e 100644 --- a/kernel/posix-cpu-timers.c +++ b/kernel/posix-cpu-timers.c @@ -549,7 +549,7 @@ static inline int expires_gt(cputime_t expires, cputime_t new_exp) /* * Insert the timer on the appropriate list before any timers that * expire later. This must be called with the tasklist_lock held - * for reading, and interrupts disabled. + * for reading, interrupts disabled and p->sighand->siglock taken. */ static void arm_timer(struct k_itimer *timer) { @@ -568,9 +568,6 @@ static void arm_timer(struct k_itimer *timer) } head += CPUCLOCK_WHICH(timer->it_clock); - BUG_ON(!irqs_disabled()); - spin_lock(&p->sighand->siglock); - listpos = head; list_for_each_entry(next, head, entry) { if (cpu_time_before(timer->it_clock, nt->expires, next->expires)) @@ -605,8 +602,6 @@ static void arm_timer(struct k_itimer *timer) break; } } - - spin_unlock(&p->sighand->siglock); } /* @@ -719,7 +714,6 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags, ret = TIMER_RETRY; } else list_del_init(&timer->it.cpu.entry); - spin_unlock(&p->sighand->siglock); /* * We need to sample the current value to convert the new @@ -773,6 +767,7 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags, * disable this firing since we are already reporting * it as an overrun (thanks to bump_cpu_timer above). */ + spin_unlock(&p->sighand->siglock); read_unlock(&tasklist_lock); goto out; } @@ -792,6 +787,7 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags, arm_timer(timer); } + spin_unlock(&p->sighand->siglock); read_unlock(&tasklist_lock); /* @@ -1205,6 +1201,7 @@ void posix_cpu_timer_schedule(struct k_itimer *timer) goto out; } read_lock(&tasklist_lock); /* arm_timer needs it. */ + spin_lock(&p->sighand->siglock); } else { read_lock(&tasklist_lock); if (unlikely(p->signal == NULL)) { @@ -1225,6 +1222,7 @@ void posix_cpu_timer_schedule(struct k_itimer *timer) clear_dead_task(timer, now); goto out_unlock; } + spin_lock(&p->sighand->siglock); cpu_timer_sample_group(timer->it_clock, p, &now); bump_cpu_timer(timer, now); /* Leave the tasklist_lock locked for the call below. */ @@ -1233,7 +1231,9 @@ void posix_cpu_timer_schedule(struct k_itimer *timer) /* * Now re-arm for the new expiry time. */ + BUG_ON(!irqs_disabled()); arm_timer(timer); + spin_unlock(&p->sighand->siglock); out_unlock: read_unlock(&tasklist_lock); -- 1.6.2.5