linux-kernel - Re: frequent lockups in 3.18rc4

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Message-ID: <20141213023252.GA2881@redhat.com>
Date:	Fri, 12 Dec 2014 21:32:52 -0500
From:	Dave Jones <davej@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Sasha Levin <sasha.levin@...cle.com>, Chris Mason <clm@...com>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Dâniel Fraga <fragabr@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: frequent lockups in 3.18rc4

On Fri, Dec 12, 2014 at 04:23:16PM -0800, Linus Torvalds wrote:
 > On Fri, Dec 12, 2014 at 3:54 PM, Sasha Levin <sasha.levin@...cle.com> wrote:
 > >
 > > I ran bisection on trinity, rather than the kernel, and got the following
 > > result:
 > 
 > Heh. That commit is pretty small, but I guess the effect of having a
 > number of regular files open and being used on the trinity loads can
 > be almost arbitrarily large.
 > 
 > Where do those files get opened? What filesystem?

in the cwd where trinity is run from. In my case, ext4

 > > I've been running trinity f2be2d5ff^ on -next for two hours now, and there's
 > > no sign of a lockup. Previously it took ~10 minutes trigger.
 > 
 > DaveJ?  Is there anything limiting the size of those files?

Nope. We could for eg, do a random truncate() with a huge size, and it would
try and create something enormous.  write()'s are limited to page size,
there might be some other syscalls I haven't added safety guards to.

	Dave

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