linux-kernel - Re: + shmem-fix-faulting-into-a-hole-while-its-punched-take-2.patch added to -mm tree

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Message-ID: <53C2FD71.7090102@oracle.com>
Date:	Sun, 13 Jul 2014 17:43:13 -0400
From:	Sasha Levin <sasha.levin@...cle.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Hugh Dickins <hughd@...gle.com>
CC:	Heiko Carstens <heiko.carstens@...ibm.com>,
	Vlastimil Babka <vbabka@...e.cz>, akpm@...ux-foundation.org,
	davej@...hat.com, koct9i@...il.com, lczerner@...hat.com,
	stable@...r.kernel.org, "linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: + shmem-fix-faulting-into-a-hole-while-its-punched-take-2.patch
 added to -mm tree

On 07/11/2014 11:59 AM, Peter Zijlstra wrote:
>>> I agree with you that "The call trace is very clear on it that its not", but
>>> > > when you have 500 call traces you really want something better than going
>>> > > through it one call trace at a time.
>> > 
>> > Points well made, and I strongly agree with Vlastimil and Sasha.
>> > There is a world of difference between a lock wanted and a lock held,
>> > and for the display of locks "held" to conceal that difference is unhelpful.
>> > It just needs one greppable word to distinguish the cases.
> So for the actual locking scenario it doesn't make a difference one way
> or another. These threads all can/could/will acquire the lock
> (eventually), so all their locking chains should be considered.

I think that the difference here is that we're not actually debugging a locking
issue, we're merely using lockdep to help with figuring out a non-locking
related bug and finding it difficult because lockdep's list of "held locks"
is really a lie :)


Thanks,
Sasha
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