Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756376Ab2BGEUx (ORCPT ); Mon, 6 Feb 2012 23:20:53 -0500 Received: from mail-bk0-f46.google.com ([209.85.214.46]:39583 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756305Ab2BGEUb (ORCPT ); Mon, 6 Feb 2012 23:20:31 -0500 Date: Tue, 7 Feb 2012 08:20:26 +0400 From: Anton Vorontsov To: KOSAKI Motohiro Cc: Oleg Nesterov , Greg KH , Arve =?utf-8?B?SGrDuG5uZXbDpWc=?= , San Mehat , Colin Cross , "Eric W. Biederman" , "Paul E. McKenney" , linux-kernel@vger.kernel.org, kernel-team@android.com, linaro-kernel@lists.linaro.org Subject: [PATCH v2 2/6] oom: Get rid of sparse warnings Message-ID: <20120207042026.GA25524@oksana.dev.rtsoft.ru> References: <20120203163056.GA4190@redhat.com> <20120206162935.GB5117@oksana.dev.rtsoft.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4016 Lines: 114 Sparse flood makes it hard to catch newly-introduced warnings. So let's fix the the sparse warnings in the oom killer: CHECK mm/oom_kill.c mm/oom_kill.c:139:20: warning: context imbalance in '__find_lock_task_mm' - wrong count at exit mm/oom_kill.c:771:9: warning: context imbalance in 'out_of_memory' - different lock contexts for basic block The first one is fixed by assuring sparse that we know that we exit with the lock held. The second one is caused by the fact that sparse isn't smart enough to handle noreturn attribute. Signed-off-by: Anton Vorontsov --- On Mon, Feb 06, 2012 at 04:33:26PM -0500, KOSAKI Motohiro wrote: > 2012/2/6 Anton Vorontsov : > > Sparse flood makes it hard to catch newly-introduced warnings. So let's > > fix the the sparse warnings in the oom killer: > > > >  CHECK   mm/oom_kill.c > >  mm/oom_kill.c:139:20: warning: context imbalance in > >          '__find_lock_task_mm' - wrong count at exit > >  mm/oom_kill.c:771:9: warning: context imbalance in 'out_of_memory' - > >          different lock contexts for basic block > > > > The first one is fixed by assuring sparse that we know that we exit > > with the lock held. > > > > The second one is caused by the fact that sparse isn't smart enough > > to handle noreturn attribute. > > > > Signed-off-by: Anton Vorontsov > > --- > >  mm/oom_kill.c |    9 ++++++++- > >  1 files changed, 8 insertions(+), 1 deletions(-) > > > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > > index 0ebb383..49569b6 100644 > > --- a/mm/oom_kill.c > > +++ b/mm/oom_kill.c > > @@ -142,8 +142,14 @@ struct task_struct *__find_lock_task_mm(struct task_struct *p) > > > >        do { > >                task_lock(t); > > -               if (likely(t->mm)) > > +               if (likely(t->mm)) { > > +                       /* > > +                        * Shut up sparse: we do know that we exit w/ the > > +                        * task locked. > > +                        */ > > +                       __release(&t->alloc_loc); > > task struct only have allock_lock, not alloc_loc. Funnily, but sparse does not care. :-) __release(foo) will work as well. Seems like sparse counts locking balance globally. This is now fixed in the patch down below, thanks for catching. > Moreover we don't release > the lock in this code path. Seems odd. Indeed. That's exactly what sparse seeing is as well. We exit without releasing the lock, which is bad (in sparse' eyes). So we lie to sparse, telling it that we do release, so it shut ups. Usually, we annotate functions with __releases() and __acquires() when when functions releases/acquires one of its arguments, but in this case the function returns a locked value, and it seems that there's no way to properly annotate this case. mm/oom_kill.c | 9 ++++++++- 1 files changed, 8 insertions(+), 1 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 0ebb383..1914367 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -142,8 +142,14 @@ struct task_struct *__find_lock_task_mm(struct task_struct *p) do { task_lock(t); - if (likely(t->mm)) + if (likely(t->mm)) { + /* + * Shut up sparse: we do know that we exit w/ the + * task locked. + */ + __release(&t->alloc_lock); return t; + } task_unlock(t); } while_each_thread(p, t); @@ -766,6 +772,7 @@ retry: dump_header(NULL, gfp_mask, order, NULL, mpol_mask); read_unlock(&tasklist_lock); panic("Out of memory and no killable processes...\n"); + return; } if (oom_kill_process(p, gfp_mask, order, points, totalpages, NULL, -- 1.7.7.6 -- 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/