linux-kernel - Re: [PATCH 1/2] break out page allocation warning code

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Message-ID: <alpine.DEB.2.00.1104191422080.510@chino.kir.corp.google.com>
Date:	Tue, 19 Apr 2011 14:23:35 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Nazarewicz <mina86@...a86.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/2] break out page allocation warning code

On Mon, 18 Apr 2011, Dave Hansen wrote:

> > It shouldn't be a follow-on patch since you're introducing a new feature 
> > here (vmalloc allocation failure warnings) and what I'm identifying is a 
> > race in the access to current->comm.  A bug fix for a race should always 
> > preceed a feature that touches the same code.
> 
> Dude.  Seriously.  Glass house!  a63d83f4
> 

Not sure what you're implying here.  The commit you've identified is the 
oom killer rewrite and the oom killer is very specific about making sure 
to always hold task_lock() whenever dereferencing ->comm, even for 
current, to guard against /proc/pid/comm or prctl().  The oom killer is 
different from your usecase, however, because we can always take 
task_lock(current) in the oom killer because it's in a blockable context, 
whereas page allocation warnings can occur in a superset.
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