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From: Willy Tarreau <w@1wt.eu>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Byungchul Park <byungchul.park@lge.com>,
	stable@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [STABLE] kernel oops which can be fixed by peterz's patches
Date: Tue, 12 Jan 2016 11:21:06 +0100	[thread overview]
Message-ID: <20160112102106.GA20507@1wt.eu> (raw)
In-Reply-To: <20160105091444.GZ6357@twins.programming.kicks-ass.net>

Hi Peter,

On Tue, Jan 05, 2016 at 10:14:44AM +0100, Peter Zijlstra wrote:
> On Tue, Jan 05, 2016 at 05:52:11PM +0900, Byungchul Park wrote:
> > 
> > Upstream commits to be applied
> > ==============================
> > 
> > e3fca9e: sched: Replace post_schedule with a balance callback list
> > 4c9a4bc: sched: Allow balance callbacks for check_class_changed()
> > 8046d68: sched,rt: Remove return value from pull_rt_task()
> > fd7a4be: sched, rt: Convert switched_{from, to}_rt() / prio_changed_rt() to balance callbacks
> > 0ea60c2: sched,dl: Remove return value from pull_dl_task()
> > 9916e21: sched, dl: Convert switched_{from, to}_dl() / prio_changed_dl() to balance callbacks
> > 
> > The reason why these should be applied
> > ======================================
> > 
> > Our products developed using 3.16 kernel, faced a kernel oops which can
> > be fixed with above upstreamed patches. The oops is caused by "Unable
> > to handle kernel NULL pointer dereference at virtual address 000000xx"
> > in the call path,
> > 
> > __sched_setscheduler()
> > 	check_class_changed()
> > 		switched_to_fair()
> > 			check_preempt_curr()
> > 				check_preempt_wakeup()
> > 					find_matching_se()
> > 						is_same_group()
> > 
> > by "if (se->cfs_rq == pse->cfs_rq) // se, pse == NULL" condition.
> 
> So the reason I didn't mark them for stable is that they were non
> trivial, however they've been in for a while now and nothing broke, so I
> suppose backporting them isn't a problem.

I didn't check the code, but for older kernels, can't we simply get rid
of the issue by adding an extra test on se/pse before dereferencing it,
even if that implies a suboptimal fix which is always better than an oops ?
I must confess I don't feel at ease with backporting so many sensitive
changes into 2.6.32!

Thanks,
Willy

  parent reply	other threads:[~2016-01-12 10:21 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-05  8:52 [STABLE] kernel oops which can be fixed by peterz's patches Byungchul Park
2016-01-05  9:14 ` Peter Zijlstra
2016-01-12  8:47   ` Byungchul Park
2016-01-12 10:21   ` Willy Tarreau [this message]
2016-01-25  7:25   ` Byungchul Park
2016-02-16  7:08     ` Byungchul Park
2016-02-16  8:44       ` Peter Zijlstra
2016-02-16 17:42         ` Greg KH
2016-02-17  0:11           ` Byungchul Park
2016-02-17  0:41             ` Greg KH
2016-02-17  2:00               ` Byungchul Park
2016-02-17  3:01                 ` Greg KH
2016-02-17  3:02                 ` Mike Galbraith
2016-02-23 21:05                   ` Ben Hutchings
2016-02-23 21:06                   ` Ben Hutchings
2016-01-05  9:16 ` [PATCH for v3.14.58 1/7] sched: Clean up idle task SMP logic Byungchul Park
2016-01-05  9:16   ` [PATCH for v3.14.58 2/7] sched: Replace post_schedule with a balance callback list Byungchul Park
2016-01-05  9:16   ` [PATCH for v3.14.58 3/7] sched: Allow balance callbacks for check_class_changed() Byungchul Park
2016-01-05  9:16   ` [PATCH for v3.14.58 4/7] sched,rt: Remove return value from pull_rt_task() Byungchul Park
2016-01-05  9:16   ` [PATCH for v3.14.58 5/7] sched, rt: Convert switched_{from, to}_rt() / prio_changed_rt() to balance callbacks Byungchul Park
2016-01-05  9:16   ` [PATCH for v3.14.58 6/7] sched,dl: Remove return value from pull_dl_task() Byungchul Park
2016-01-05  9:16   ` [PATCH for v3.14.58 7/7] sched, dl: Convert switched_{from, to}_dl() / prio_changed_dl() to balance callbacks Byungchul Park
2016-01-05  9:24 ` [PATCH for v3.18.25 1/6] sched: Replace post_schedule with a balance callback list Byungchul Park
2016-01-05  9:24   ` [PATCH for v3.18.25 2/6] sched: Allow balance callbacks for check_class_changed() Byungchul Park
2016-01-05  9:24   ` [PATCH for v3.18.25 3/6] sched,rt: Remove return value from pull_rt_task() Byungchul Park
2016-01-05  9:24   ` [PATCH for v3.18.25 4/6] sched, rt: Convert switched_{from, to}_rt() / prio_changed_rt() to balance callbacks Byungchul Park
2016-01-05  9:24   ` [PATCH for v3.18.25 5/6] sched,dl: Remove return value from pull_dl_task() Byungchul Park
2016-01-05  9:24   ` [PATCH for v3.18.25 6/6] sched, dl: Convert switched_{from, to}_dl() / prio_changed_dl() to balance callbacks Byungchul Park
2016-03-01  8:15 ` [STABLE] kernel oops which can be fixed by peterz's patches Greg KH
2016-07-18  6:31   ` Byungchul Park
2016-07-18 12:09     ` Greg KH
2016-07-18 23:59       ` Byungchul Park
2016-06-13 18:31 ` Ben Hutchings

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