From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757927Ab0CaAkD (ORCPT ); Tue, 30 Mar 2010 20:40:03 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:48306 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755585Ab0CaAj4 (ORCPT ); Tue, 30 Mar 2010 20:39:56 -0400 Date: Tue, 30 Mar 2010 17:37:21 -0400 From: Andrew Morton To: KAMEZAWA Hiroyuki Cc: "Michael S. Tsirkin" , cl@linux-foundation.org, lee.schermerhorn@hp.com, rientjes@google.com, Hugh Dickins , Rik van Riel , Minchan Kim , Andrea Arcangeli , "David S. Miller" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Troels Liebe Bentsen , linux-bluetooth@vger.kernel.org Subject: Re: [PATCH] exit: fix oops in sync_mm_rss Message-Id: <20100330173721.cbd442cb.akpm@linux-foundation.org> In-Reply-To: <20100331092815.c8b9d89c.kamezawa.hiroyu@jp.fujitsu.com> References: <20100316170808.GA29400@redhat.com> <20100330135634.09e6b045.akpm@linux-foundation.org> <20100331092815.c8b9d89c.kamezawa.hiroyu@jp.fujitsu.com> X-Mailer: Sylpheed 2.7.1 (GTK+ 2.18.7; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 31 Mar 2010 09:28:15 +0900 KAMEZAWA Hiroyuki wrote: > On Tue, 30 Mar 2010 13:56:34 -0700 > Andrew Morton wrote: > > > That new BUG_ON() is triggering in Troels's machine when a bluetooth > > keyboard is enabled or disabled. See > > (https://bugzilla.kernel.org/show_bug.cgi?id=15648. > > > > I guess the question is: how did a kernel thread get a non-zero > > task->rss_stat.count[i]? If that's expected and OK then we will need > > to take some kernel-thread-avoidance action there. > > > It seems my fault that it's not initialized to be 0 at do_fork(), copy_process. > > About do_exit, do_exit() does this check. So, tsk->mm can be NULL. > > 949 if (group_dead) { > 950 hrtimer_cancel(&tsk->signal->real_timer); > 951 exit_itimers(tsk->signal); > 952 if (tsk->mm) > 953 setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm); > 954 } > > > Could whoever fixes this please also make __sync_task_rss_stat() > > static. > > > Ah, yes. I should do so. > > > I'll toss this over to Rafael/Maciej for tracking as a post-2.6.33 > > regression. > > > > Thanks. > > > > > == > > task->rss_stat wasn't initialized to 0 at copy_process(). > at exit, tsk->mm may be NULL. > And __sync_task_rss_stat() should be static. > > Signed-off-by: KAMEZAWA Hiroyuki > --- > kernel/exit.c | 3 ++- > kernel/fork.c | 3 +++ > mm/memory.c | 2 +- > 3 files changed, 6 insertions(+), 2 deletions(-) > > Index: mmotm-2.6.34-Mar24/kernel/exit.c > =================================================================== > --- mmotm-2.6.34-Mar24.orig/kernel/exit.c > +++ mmotm-2.6.34-Mar24/kernel/exit.c > @@ -950,7 +950,8 @@ NORET_TYPE void do_exit(long code) > > acct_update_integrals(tsk); > /* sync mm's RSS info before statistics gathering */ > - sync_mm_rss(tsk, tsk->mm); > + if (tsk->mm) > + sync_mm_rss(tsk, tsk->mm); > group_dead = atomic_dec_and_test(&tsk->signal->live); > if (group_dead) { > hrtimer_cancel(&tsk->signal->real_timer); > Index: mmotm-2.6.34-Mar24/mm/memory.c > =================================================================== > --- mmotm-2.6.34-Mar24.orig/mm/memory.c > +++ mmotm-2.6.34-Mar24/mm/memory.c > @@ -124,7 +124,7 @@ core_initcall(init_zero_pfn); > > #if defined(SPLIT_RSS_COUNTING) > > -void __sync_task_rss_stat(struct task_struct *task, struct mm_struct *mm) > +static void __sync_task_rss_stat(struct task_struct *task, struct mm_struct *mm) > { > int i; > > Index: mmotm-2.6.34-Mar24/kernel/fork.c > =================================================================== > --- mmotm-2.6.34-Mar24.orig/kernel/fork.c > +++ mmotm-2.6.34-Mar24/kernel/fork.c > @@ -1060,6 +1060,9 @@ static struct task_struct *copy_process( > p->prev_utime = cputime_zero; > p->prev_stime = cputime_zero; > #endif > +#if defined(SPLIT_RSS_COUNTING) > + memset(&p->rss_stat, 0, sizeof(p->rss_stat)); > +#endif > > p->default_timer_slack_ns = current->timer_slack_ns; OK, so the kenrel thread inherited a non-zero rss_stat from a userspace parent? With this fixed, the test for non-zero tsk->mm is't really needed in do_exit(), is it? I guess it makes sense though - sync_mm_rss() only really works for kernel threads by luck..