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: <alpine.LSU.2.11.1407110745430.2054@eggly.anvils>
Date:	Fri, 11 Jul 2014 07:55:50 -0700 (PDT)
From:	Hugh Dickins <hughd@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Sasha Levin <sasha.levin@...cle.com>,
	Hugh Dickins <hughd@...gle.com>,
	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 Fri, 11 Jul 2014, Sasha Levin wrote:
> 
> There's no easy way to see whether a given task is actually holding a lock or
> is just blocking on it without going through all those tasks one by one and
> looking at their trace.
> 
> 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.

(Though I didn't find "The call trace is very clear on it that its not",
I thought it too was telling me that the lock was already held somehow.)

Hugh
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