Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756894AbZLMBcl (ORCPT ); Sat, 12 Dec 2009 20:32:41 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756577AbZLMBck (ORCPT ); Sat, 12 Dec 2009 20:32:40 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:40382 "HELO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754316AbZLMBci (ORCPT ); Sat, 12 Dec 2009 20:32:38 -0500 From: "Rafael J. Wysocki" To: Ingo Molnar Subject: [PATCH] sched: Make wakeup side variants of completion API irq safe (was: Re: spinlock in completion_done()) Date: Sun, 13 Dec 2009 00:07:30 +0100 User-Agent: KMail/1.12.3 (Linux/2.6.32-rjw; KDE/4.3.3; x86_64; ; ) Cc: Alan Stern , Linus Torvalds , Zhang Rui , LKML , ACPI Devel Maling List , pm list , Peter Zijlstra , David Chinner , Lachlan McIlroy References: <200912092337.52492.rjw@sisk.pl> <20091210075947.GD25549@elte.hu> In-Reply-To: <20091210075947.GD25549@elte.hu> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200912130007.30541.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3293 Lines: 102 On Thursday 10 December 2009, Ingo Molnar wrote: > > * Rafael J. Wysocki wrote: > > > On Wednesday 09 December 2009, Ingo Molnar wrote: > > > > > > * Rafael J. Wysocki wrote: > > > > > > > On Tuesday 08 December 2009, Alan Stern wrote: > > > > > On Tue, 8 Dec 2009, Rafael J. Wysocki wrote: > > > > > > > > > > > BTW, is there a good reason why completion_done() doesn't use spin_lock_irqsave > > > > > > and spin_unlock_irqrestore? complete() and complete_all() use them, so why not > > > > > > here? > > > > > > > > > > And likewise in try_wait_for_completion(). It looks like a bug. Maybe > > > > > these routines were not intended to be called with interrupts disabled, > > > > > but that requirement doesn't seem to be documented. And it isn't a > > > > > natural requirement anyway. > > > > > > > > OK, let's ask Ingo about that. > > > > > > > > Ingo, is there any particular reason why completion_done() and > > > > try_wait_for_completion() don't use spin_lock_irqsave() and > > > > spin_unlock_irqrestore()? > > > > > > that's a bug that should be fixed - all the wakeup side (and atomic) > > > variants of completetion API should be irq safe. > > > > > > It appears that these new completion APIs were added via the XFS tree > > > about a year ago: > > > > > > 39d2f1a: [XFS] extend completions to provide XFS object flush requirements > > > > > > Please Cc: scheduler folks to all scheduler patches. > > > > If you haven't fixed it locally yet, would you mind me posting a fix? > > I wouldnt mind it at all. Is appended. Thanks, Rafael --- From: Rafael J. Wysocki Subject: sched: Make wakeup side variants of completion API irq safe All the wakeup side variants of the completion API shoild be irq safe, but completion_done() and try_wait_for_completion() aren't. Fix the problem by making them use spin_lock_irqsave() and spin_lock_irqrestore(). Signed-off-by: Rafael J. Wysocki --- kernel/sched.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) Index: linux-2.6/kernel/sched.c =================================================================== --- linux-2.6.orig/kernel/sched.c +++ linux-2.6/kernel/sched.c @@ -5931,14 +5931,15 @@ EXPORT_SYMBOL(wait_for_completion_killab */ bool try_wait_for_completion(struct completion *x) { + unsigned long flags; int ret = 1; - spin_lock_irq(&x->wait.lock); + spin_lock_irqsave(&x->wait.lock, flags); if (!x->done) ret = 0; else x->done--; - spin_unlock_irq(&x->wait.lock); + spin_unlock_irqrestore(&x->wait.lock, flags); return ret; } EXPORT_SYMBOL(try_wait_for_completion); @@ -5953,12 +5954,13 @@ EXPORT_SYMBOL(try_wait_for_completion); */ bool completion_done(struct completion *x) { + unsigned long flags; int ret = 1; - spin_lock_irq(&x->wait.lock); + spin_lock_irqsave(&x->wait.lock, flags); if (!x->done) ret = 0; - spin_unlock_irq(&x->wait.lock); + spin_unlock_irqrestore(&x->wait.lock, flags); return ret; } EXPORT_SYMBOL(completion_done); -- 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/