linux-kernel - Re: [resend][PATCH 2/4] Revert "oom: deprecate oom

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Message-ID: <alpine.DEB.2.00.1011150152490.2986@chino.kir.corp.google.com>
Date:	Mon, 15 Nov 2010 01:59:12 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [resend][PATCH 2/4] Revert "oom: deprecate oom_adj tunable"

On Mon, 15 Nov 2010, KOSAKI Motohiro wrote:

> At v2.6.36-rc1, oom-killer doesn't work at all because YOU BROKE.
> And I was working on fixing it.
> 
> 2010-08-19
> http://marc.info/?t=128223176900001&r=1&w=2

This existed before my oom killer rewrite, it was only noticed because the 
rewrite enabled oom_dump_tasks by default.

> http://marc.info/?t=128221532700003&r=1&w=2

Yes, tasklist_lock was dropped in a mismerge of my patches when posting 
them.  Thanks for finding it and posting a patch, I appreciate it.

> http://marc.info/?t=128221532500008&r=1&w=2
> 

Yes, if a task was racing between oom_kill_process() and oom_kill_task() 
and all threads had dropped its mm between calls then there was a NULL 
pointer dereference, thanks for fixing that as well.

> However, You submitted new crap before the fixing. 
> 
> 2010-08-15
> http://marc.info/?t=128184669600001&r=1&w=2
> 

This isn't "crap", this is a necessary bit to ensure that tasks that share 
an ->mm with a task immune from kill aren't killed themselves since we 
can't free the memory.  We came to the consensus that it would be better 
to count the tasks that are OOM_DISABLE in the mm_struct to avoid the 
O(2*n) tasklist scan.

> If you tested mainline a bit, you could find the problem quickly.
> You should have fixed mainline kernel at first.
> 

Thanks for finding a couple fixes during the 2.6.36-rc1 when the rewrite 
was first merged, it's much appreciated!
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