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Subject: Re: [PATCH 03/29] mm: allow PF_MEMALLOC from softirq context
From: Arjan van de Ven <arjan@infradead.org>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org,
       Trond Myklebust <trond.myklebust@fys.uio.no>,
       Thomas Graf <tgraf@suug.ch>, David Miller <davem@davemloft.net>
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	 <20070221144841.823705000@taijtu.programming.kicks-ass.net>
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Organization: Intel International BV
Date: Wed, 21 Feb 2007 16:53:37 +0100
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> Index: linux-2.6-git/kernel/softirq.c
> ===================================================================
> --- linux-2.6-git.orig/kernel/softirq.c	2006-12-14 10:02:18.000000000 +0100
> +++ linux-2.6-git/kernel/softirq.c	2006-12-14 10:02:52.000000000 +0100
> @@ -209,6 +209,8 @@ asmlinkage void __do_softirq(void)
>  	__u32 pending;
>  	int max_restart = MAX_SOFTIRQ_RESTART;
>  	int cpu;
> +	unsigned long pflags = current->flags;
> +	current->flags &= ~PF_MEMALLOC;
>  
>  	pending = local_softirq_pending();
>  	account_system_vtime(current);
> @@ -247,6 +249,7 @@ restart:
>  
>  	account_system_vtime(current);
>  	_local_bh_enable();
> +	current->flags = pflags;

this wipes out all the flags in one go.... evil.
What if something just selected this process for OOM killing? you nuke
that flag here again. Would be nicer if only the PF_MEMALLOC bit got
inherited in the restore path..