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

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Message-ID: <1303267562.5076.1004.camel@nimitz>
Date:	Tue, 19 Apr 2011 19:46:02 -0700
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	David Rientjes <rientjes@...gle.com>, 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>,
	John Stultz <johnstul@...ibm.com>
Subject: Re: [PATCH 1/2] break out page allocation warning code

On Wed, 2011-04-20 at 11:19 +0900, KOSAKI Motohiro wrote:
> > +     memcpy(tmp_comm, tsk->comm_buf, TASK_COMM_LEN);
> > +     tsk->comm = tmp;
> >       /*
> > -      * Threads may access current->comm without holding
> > -      * the task lock, so write the string carefully.
> > -      * Readers without a lock may see incomplete new
> > -      * names but are safe from non-terminating string reads.
> > +      * Make sure no one is still looking at tsk->comm_buf
> >        */
> > -     memset(tsk->comm, 0, TASK_COMM_LEN);
> > -     wmb();
> > -     strlcpy(tsk->comm, buf, sizeof(tsk->comm));
> > +     synchronize_rcu();
> 
> The doc says,
> 
> /**
>  * synchronize_rcu - wait until a grace period has elapsed.

Yeah, yeah... see "completely untested". :)

I'll see if dropping the locks or something else equally hackish can
help.  

-- Dave

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