linux-kernel - Re: [4.4-rc7] spinlock recursion while oom'ing.

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Message-ID: <20160105172136.GA28066@codemonkey.org.uk>
Date:	Tue, 5 Jan 2016 12:21:36 -0500
From:	Dave Jones <davej@...emonkey.org.uk>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
	David Rientjes <rientjes@...gle.com>
Subject: Re: [4.4-rc7] spinlock recursion while oom'ing.

On Tue, Jan 05, 2016 at 05:35:36PM +0100, Michal Hocko wrote:
 > [CCing David]
 > 
 > On Sun 03-01-16 17:27:28, Dave Jones wrote:
 > > This is an odd one..
 > > 
 > > Out of memory: Kill process 5861 (trinity-c10) score 504 or sacrifice child
 > > BUG: spinlock recursion on CPU#1, trinity-c8/8828
 > >  lock: 0xffff8800a3635410, .magic: dead4ead, .owner: trinity-c8/8828, .owner_cpu: 1
 > > CPU: 1 PID: 8828 Comm: trinity-c8 Not tainted 4.4.0-rc7-gelk-debug+ #3 
 > >  00000000000001f8 ffff8800968d7808 ffffffff9a4d4451 ffff8800a3635410
 > >  ffff8800968d7838 ffffffff9a117b36 ffff8800a3635410 ffff8800a3635420
 > >  ffff8800a3635410 ffff8800a3635398 ffff8800968d7870 ffffffff9a117d63
 > > Call Trace:
 > >  [<ffffffff9a4d4451>] dump_stack+0x4e/0x7d
 > >  [<ffffffff9a117b36>] spin_dump+0xc6/0x130
 > >  [<ffffffff9a117d63>] do_raw_spin_lock+0x163/0x1a0
 > >  [<ffffffff9aae15ef>] _raw_spin_lock+0x1f/0x30
 > >  [<ffffffff9a2271cb>] find_lock_task_mm+0x5b/0xd0
 > >  [<ffffffff9a227cc0>] oom_kill_process+0x2a0/0x660
 > >  [<ffffffff9a22855d>] out_of_memory+0x45d/0x4b0
 > 
 > Hmm, this is indeed weird. We are certainly not holding task_lock during
 > the allocation AFAICS (if yes that would be a GFP_KERNEL allocation with
 > a spinlock so I would assume a blow up earlier than when entering OOM).
 > 
 > oom_badness unlocks in all paths AFAICS. oom_kill_process will lock the
 > victim again but it releases the lock as well. dump_tasks the same.

sorry, turned out to be a (broken) leftover debugging patch that I'd had applied
that I thought I'd dropped but hadn't..

	Dave
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