netdev - Re: [PATCH] Fix soft lockups/OOM issues w/ unix garbage collector

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Date:	Mon, 01 Dec 2008 13:16:46 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	dannf@...com
Cc:	netdev@...r.kernel.org, eteo@...hat.com
Subject: Re: [PATCH] Fix soft lockups/OOM issues w/ unix garbage collector

From: dann frazier <dannf@...com>
Date: Mon, 1 Dec 2008 13:17:04 -0700

> On Wed, Nov 26, 2008 at 03:32:43PM -0800, David Miller wrote:
> > From: dann frazier <dannf@...nf.org>
> > Date: Wed, 26 Nov 2008 10:04:02 -0700
> > 
> > > This is an implementation of David Miller's suggested fix in:
> > >   https://bugzilla.redhat.com/show_bug.cgi?id=470201
> > > 
> > > It has been updated to use wait_event() instead of
> > > wait_event_interruptible().
> > > 
> > > Paraphrasing the description from the above report, it makes sendmsg()
> > > block while UNIX garbage collection is in progress. This avoids a
> > > situation where child processes continue to queue new FDs over a
> > > AF_UNIX socket to a parent which is in the exit path and running
> > > garbage collection on these FDs. This contention can result in soft
> > > lockups and oom-killing of unrelated processes.
> > > 
> > > Signed-off-by: dann frazier <dannf@...com>
> > 
> > Applied, thanks a lot Dann.
> 
> I was asked if this patch may introduce blocking during operations on
> non-blocking sockets. Should we update wait_for_unix_gc (and its
> callers) to something like this?

No, it's just like waiting for a GFP_KERNEL memory allocation.
Non-blocking doesn't mean "never will sleep".
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