linux-kernel - Re: [patch 4/6] x86: finish user fault error path with fatal signal

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Message-ID: <51F6BBEC.5070203@gmail.com>
Date:	Mon, 29 Jul 2013 15:01:00 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	Johannes Weiner <hannes@...xchg.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>,
	David Rientjes <rientjes@...gle.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	azurIt <azurit@...ox.sk>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, x86@...nel.org,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	kosaki.motohiro@...il.com
Subject: Re: [patch 4/6] x86: finish user fault error path with fatal signal

(7/25/13 6:25 PM), Johannes Weiner wrote:
> The x86 fault handler bails in the middle of error handling when the
> task has a fatal signal pending.  For a subsequent patch this is a
> problem in OOM situations because it relies on
> pagefault_out_of_memory() being called even when the task has been
> killed, to perform proper per-task OOM state unwinding.
> 
> Shortcutting the fault like this is a rather minor optimization that
> saves a few instructions in rare cases.  Just remove it for
> user-triggered faults.
> 
> Use the opportunity to split the fault retry handling from actual
> fault errors and add locking documentation that reads suprisingly
> similar to ARM's.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Acked-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>

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