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From: Sasha Levin <sasha.levin@oracle.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Davidlohr Bueso <davidlohr@hp.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
	Michel Lespinasse <walken@google.com>,
	Rik van Riel <riel@redhat.com>, Vlastimil Babka <vbabka@suse.cz>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: mm: mmap_sem lock assertion failure in __mlock_vma_pages_range
Date: Tue, 11 Mar 2014 16:35:55 -0400	[thread overview]
Message-ID: <531F73AB.5060402@oracle.com> (raw)
In-Reply-To: <20140311133051.bf5ca716ef189746ebcff431@linux-foundation.org>

On 03/11/2014 04:30 PM, Andrew Morton wrote:
> I worry about what happens if __get_user_pages decides to do
>
> 				if (ret & VM_FAULT_RETRY) {
> 					if (nonblocking)
> 						*nonblocking = 0;
> 					return i;
> 				}
>
> uh-oh, that just cleared __mm_populate()'s `locked' variable and we'll
> forget to undo mmap_sem.  That won't explain this result, but it's a
> potential problem.

That's actually seems right because if 'ret & VM_FAULT_RETRY' is true it means that
lock_page_or_retry() was supposed to release mmap_sem for us.


Thanks,
Sasha

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WARNING: multiple messages have this Message-ID (diff)
From: Sasha Levin <sasha.levin@oracle.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Davidlohr Bueso <davidlohr@hp.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
	Michel Lespinasse <walken@google.com>,
	Rik van Riel <riel@redhat.com>, Vlastimil Babka <vbabka@suse.cz>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: mm: mmap_sem lock assertion failure in __mlock_vma_pages_range
Date: Tue, 11 Mar 2014 16:35:55 -0400	[thread overview]
Message-ID: <531F73AB.5060402@oracle.com> (raw)
In-Reply-To: <20140311133051.bf5ca716ef189746ebcff431@linux-foundation.org>

On 03/11/2014 04:30 PM, Andrew Morton wrote:
> I worry about what happens if __get_user_pages decides to do
>
> 				if (ret & VM_FAULT_RETRY) {
> 					if (nonblocking)
> 						*nonblocking = 0;
> 					return i;
> 				}
>
> uh-oh, that just cleared __mm_populate()'s `locked' variable and we'll
> forget to undo mmap_sem.  That won't explain this result, but it's a
> potential problem.

That's actually seems right because if 'ret & VM_FAULT_RETRY' is true it means that
lock_page_or_retry() was supposed to release mmap_sem for us.


Thanks,
Sasha

  reply	other threads:[~2014-03-11 20:36 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-03-11 19:39 mm: mmap_sem lock assertion failure in __mlock_vma_pages_range Sasha Levin
2014-03-11 19:39 ` Sasha Levin
2014-03-11 20:07 ` Davidlohr Bueso
2014-03-11 20:07   ` Davidlohr Bueso
2014-03-11 20:12   ` Sasha Levin
2014-03-11 20:12     ` Sasha Levin
2014-03-11 20:21     ` Davidlohr Bueso
2014-03-11 20:21       ` Davidlohr Bueso
2014-03-11 20:30   ` Andrew Morton
2014-03-11 20:30     ` Andrew Morton
2014-03-11 20:35     ` Sasha Levin [this message]
2014-03-11 20:35       ` Sasha Levin
2014-03-11 20:42     ` Davidlohr Bueso
2014-03-11 20:42       ` Davidlohr Bueso
2014-03-11 20:45     ` Sasha Levin
2014-03-11 20:45       ` Sasha Levin
2014-03-11 20:47       ` Davidlohr Bueso
2014-03-11 20:47         ` Davidlohr Bueso
2014-03-11 20:57         ` Dave Jones
2014-03-11 20:57           ` Dave Jones
2014-03-11 21:02         ` Sasha Levin
2014-03-11 21:02           ` Sasha Levin
2014-03-11 21:45           ` Davidlohr Bueso
2014-03-11 21:45             ` Davidlohr Bueso
2014-03-11 22:20             ` Sasha Levin
2014-03-11 22:20               ` Sasha Levin
2014-03-13 19:00               ` Davidlohr Bueso
2014-03-13 19:00                 ` Davidlohr Bueso
2014-03-13 20:57                 ` Hugh Dickins
2014-03-13 20:57                   ` Hugh Dickins
2014-03-14 16:14                   ` Sasha Levin
2014-03-14 16:14                     ` Sasha Levin
2014-03-11 21:59   ` Michel Lespinasse
2014-03-11 21:59     ` Michel Lespinasse

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