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From: Sasha Levin <sasha.levin@oracle.com>
To: Peter Zijlstra <peterz@infradead.org>, Hugh Dickins <hughd@google.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	akpm@linux-foundation.org, davej@redhat.com, koct9i@gmail.com,
	lczerner@redhat.com, stable@vger.kernel.org,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: + shmem-fix-faulting-into-a-hole-while-its-punched-take-2.patch added to -mm tree
Date: Sun, 13 Jul 2014 17:43:13 -0400	[thread overview]
Message-ID: <53C2FD71.7090102@oracle.com> (raw)
In-Reply-To: <20140711155958.GR20603@laptop.programming.kicks-ass.net>

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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WARNING: multiple messages have this Message-ID (diff)
From: Sasha Levin <sasha.levin@oracle.com>
To: Peter Zijlstra <peterz@infradead.org>, Hugh Dickins <hughd@google.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	akpm@linux-foundation.org, davej@redhat.com, koct9i@gmail.com,
	lczerner@redhat.com, stable@vger.kernel.org,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: + shmem-fix-faulting-into-a-hole-while-its-punched-take-2.patch added to -mm tree
Date: Sun, 13 Jul 2014 17:43:13 -0400	[thread overview]
Message-ID: <53C2FD71.7090102@oracle.com> (raw)
In-Reply-To: <20140711155958.GR20603@laptop.programming.kicks-ass.net>

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

  reply	other threads:[~2014-07-13 22:05 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-07-02 19:25 + shmem-fix-faulting-into-a-hole-while-its-punched-take-2.patch added to -mm tree akpm
2014-07-09  4:03 ` Sasha Levin
2014-07-09  4:03   ` Sasha Levin
2014-07-09  6:35   ` Hugh Dickins
2014-07-09  6:35     ` Hugh Dickins
2014-07-09  9:50     ` Vlastimil Babka
2014-07-09  9:50       ` Vlastimil Babka
2014-07-09 12:47       ` Sasha Levin
2014-07-09 12:47         ` Sasha Levin
2014-07-09 16:03         ` Sasha Levin
2014-07-09 16:35           ` Vlastimil Babka
2014-07-09 16:35             ` Vlastimil Babka
2014-07-09 17:05             ` Hugh Dickins
2014-07-09 17:05               ` Hugh Dickins
2014-07-10  1:04               ` Hugh Dickins
2014-07-10  1:04                 ` Hugh Dickins
2014-07-10  7:37           ` Hugh Dickins
2014-07-10  7:37             ` Hugh Dickins
2014-07-10 12:46             ` Sasha Levin
2014-07-10 12:46               ` Sasha Levin
2014-07-10 17:21               ` Sasha Levin
2014-07-10 17:21                 ` Sasha Levin
2014-07-10 17:55                 ` Hugh Dickins
2014-07-10 17:55                   ` Hugh Dickins
2014-07-10 18:14                   ` Sasha Levin
2014-07-10 18:52                     ` Hugh Dickins
2014-07-10 18:52                       ` Hugh Dickins
2014-07-10 19:02                       ` Sasha Levin
2014-07-10 19:02                         ` Sasha Levin
2014-07-10 19:06                         ` Hugh Dickins
2014-07-10 19:06                           ` Hugh Dickins
2014-07-10 19:09                           ` Sasha Levin
2014-07-10 19:09                             ` Sasha Levin
2014-07-10 19:56                             ` Hugh Dickins
2014-07-10 19:56                               ` Hugh Dickins
2014-07-11  8:25                         ` Peter Zijlstra
2014-07-11  8:25                           ` Peter Zijlstra
2014-07-11  8:33                           ` Vlastimil Babka
2014-07-11  8:33                             ` Vlastimil Babka
2014-07-11  8:38                             ` Peter Zijlstra
2014-07-11  8:38                               ` Peter Zijlstra
2014-07-11  8:51                               ` Vlastimil Babka
2014-07-11  8:51                                 ` Vlastimil Babka
2014-07-11 12:22                           ` Sasha Levin
2014-07-11 12:22                             ` Sasha Levin
2014-07-11 14:55                             ` Hugh Dickins
2014-07-11 14:55                               ` Hugh Dickins
2014-07-11 15:59                               ` Peter Zijlstra
2014-07-11 15:59                                 ` Peter Zijlstra
2014-07-13 21:43                                 ` Sasha Levin [this message]
2014-07-13 21:43                                   ` Sasha Levin
2014-07-14 10:10                                   ` Peter Zijlstra
2014-07-10 20:06                       ` Hugh Dickins
2014-07-10 20:06                         ` Hugh Dickins
2014-07-11  6:59                       ` Hugh Dickins
2014-07-11  6:59                         ` Hugh Dickins

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