linux-kernel - Re: s/PF_BORROWED_MM/PF_KTHREAD/ (was: kernel warning: tried to kill an mm-less task!)

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Date:	Tue, 15 Apr 2008 13:10:48 -0400
From:	Jeff Dike <jdike@...toit.com>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Li Zefan <lizf@...fujitsu.com>, balbir@...ux.vnet.ibm.com,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Pavel Emelianov <xemul@...nvz.org>,
	Roland McGrath <roland@...hat.com>
Subject: Re: s/PF_BORROWED_MM/PF_KTHREAD/ (was: kernel warning: tried to
	kill an mm-less task!)

On Tue, Apr 15, 2008 at 02:19:05PM +0400, Oleg Nesterov wrote:
> First, include/asm-um/mmu_context.h:activate_mm() doesn't look right to me,
> use_mm() does switch_mm(), not activate_mm(), so I think we can do
> 
> 	--- include/asm-um/mmu_context.h	2008-02-17 23:40:08.000000000 +0300
> 	+++ -	2008-04-15 13:35:34.089295980 +0400
> 	@@ -29,7 +29,7 @@ static inline void activate_mm(struct mm
> 		 * host. Since they're very expensive, we want to avoid that as far as
> 		 * possible.
> 		 */
> 	-	if (old != new && (current->flags & PF_BORROWED_MM))
> 	+	if (old != new)
> 			__switch_mm(&new->context.id);
> 	 
> 		arch_dup_mmap(old, new);

I'm thinking I can just change this to call switch_mm, getting rid of
the old != new test too.

Plus, you can get rid of the comment in use_mm about UML needing
PF_BORROWED_MM.

I'll test this to make sure.

			Jeff

-- 
Work email - jdike at linux dot intel dot com
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