linux-kernel - Re: [patch 1/5] oom: cleanup android low memory killer

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Message-ID: <20090504231626.GA27123@kroah.com>
Date:	Mon, 4 May 2009 16:16:26 -0700
From:	Greg KH <greg@...ah.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Arve Hjønnevåg <arve@...roid.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>, San Mehat <san@...roid.com>,
	linux-kernel@...r.kernel.org, Greg KH <gregkh@...e.de>
Subject: Re: [patch 1/5] oom: cleanup android low memory killer

On Mon, May 04, 2009 at 04:12:57PM -0700, David Rientjes wrote:
> On Mon, 4 May 2009, Greg KH wrote:
> 
> > > This patch in the series is really more of a convenience than anything 
> > > else since it doesn't change anything functionally.  I had to modify the 
> > > lowmemorykiller later because there's a potential for a NULL pointer from 
> > > dereferencing p->mm without holding task_lock(p) and also because I moved 
> > > oomkilladj from struct task_struct to struct mm_struct.
> > 
> > Is this still the case on top of Arve's changes?
> > 
> 
> Yeah, the first of two patches Arve just sent is broken:

Ok, care to work with Arve to come up with a series that both of you
agree will work properly?

> > Right now, people are still arguing that the android low memory driver
> > is not needed, but something is, yet no one has proposed a viable
> > solution for all parties :(
> > 
> 
> There was an interest in a low mem userspace notifier that applications 
> can poll() on at configurable low mem levels to react accordingly.  This 
> would probably address the problem that the Android team is trying to fix.

Yes, I think it would.

> Regardless, my patchset includes two fixes for current bugs in the oom 
> killer: a possible NULL pointer when /proc/sys/vm/oom_dump_tasks is 
> enabled and a possible livelock when killing a task that shares memory 
> with an OOM_DISABLE task.  I'm not really interested in seeing who can get 
> their patches into the staging tree first, I'm more concerned about fixing 
> the oom killer.

Agreed, working with Arve on this would be most appreciated.

thanks,

greg k-h
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