Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757531Ab1DZTux (ORCPT ); Tue, 26 Apr 2011 15:50:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:26779 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756385Ab1DZTuu (ORCPT ); Tue, 26 Apr 2011 15:50:50 -0400 Date: Tue, 26 Apr 2011 21:49:25 +0200 From: Oleg Nesterov To: Linus Torvalds , Andrew Morton Cc: Tejun Heo , "Nikita V. Youshchenko" , Matt Fleming , linux-kernel@vger.kernel.org Subject: [PATCH v2 3/6] signal: do_sigtimedwait() needs retarget_shared_pending() Message-ID: <20110426194925.GD8520@redhat.com> References: <20110418134421.GA15951@redhat.com> <20110418173224.GA27918@redhat.com> <20110423175901.GA484@redhat.com> <20110426194822.GA8520@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110426194822.GA8520@redhat.com> 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 Content-Length: 2884 Lines: 80 do_sigtimedwait() changes current->blocked and thus it needs set_current_blocked()->retarget_shared_pending(). We could use set_current_blocked() directly. It is fine to change ->real_blocked from all-zeroes to ->blocked and vice versa lockless, but this is not immediately clear, looks racy, and needs a huge comment to explain why this is correct. To keep the things simple this patch adds the new static helper, __set_task_blocked() which should be called with ->siglock held. This way we can change both ->real_blocked and ->blocked atomically under ->siglock as the current code does. This is more understandable. Signed-off-by: Oleg Nesterov Acked-by: Tejun Heo Reviewed-by: Matt Fleming --- kernel/signal.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) --- sigprocmask/kernel/signal.c~3_sigtimedwait_retarget 2011-04-26 19:53:42.000000000 +0200 +++ sigprocmask/kernel/signal.c 2011-04-26 19:53:55.000000000 +0200 @@ -2115,11 +2115,8 @@ long do_no_restart_syscall(struct restar return -EINTR; } -void set_current_blocked(const sigset_t *newset) +static void __set_task_blocked(struct task_struct *tsk, const sigset_t *newset) { - struct task_struct *tsk = current; - - spin_lock_irq(&tsk->sighand->siglock); if (signal_pending(tsk) && !thread_group_empty(tsk)) { sigset_t newblocked; signandsets(&newblocked, newset, ¤t->blocked); @@ -2127,6 +2124,14 @@ void set_current_blocked(const sigset_t } tsk->blocked = *newset; recalc_sigpending(); +} + +void set_current_blocked(const sigset_t *newset) +{ + struct task_struct *tsk = current; + + spin_lock_irq(&tsk->sighand->siglock); + __set_task_blocked(tsk, newset); spin_unlock_irq(&tsk->sighand->siglock); } @@ -2343,7 +2348,8 @@ int do_sigtimedwait(const sigset_t *whic /* * None ready, temporarily unblock those we're interested * while we are sleeping in so that we'll be awakened when - * they arrive. + * they arrive. Unblocking is always fine, we can avoid + * set_current_blocked(). */ tsk->real_blocked = tsk->blocked; sigandsets(&tsk->blocked, &tsk->blocked, &mask); @@ -2353,10 +2359,9 @@ int do_sigtimedwait(const sigset_t *whic timeout = schedule_timeout_interruptible(timeout); spin_lock_irq(&tsk->sighand->siglock); - sig = dequeue_signal(tsk, &mask, info); - tsk->blocked = tsk->real_blocked; + __set_task_blocked(tsk, &tsk->real_blocked); siginitset(&tsk->real_blocked, 0); - recalc_sigpending(); + sig = dequeue_signal(tsk, &mask, info); } spin_unlock_irq(&tsk->sighand->siglock); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/