From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <owner-linux-mm@kvack.org>
Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19])
	by kanga.kvack.org (Postfix) with ESMTP id A9ADD8D003A
	for <linux-mm@kvack.org>; Tue, 15 Mar 2011 14:04:58 -0400 (EDT)
Date: Tue, 15 Mar 2011 19:03:44 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v2 2.6.38-rc8-tip 3/20] 3: uprobes: Breakground page
 replacement.
In-Reply-To: <20110315175048.GC24254@linux.vnet.ibm.com>
Message-ID: <alpine.LFD.2.00.1103151902020.2787@localhost6.localdomain6>
References: <20110314133403.27435.7901.sendpatchset@localhost6.localdomain6> <20110314133433.27435.49566.sendpatchset@localhost6.localdomain6> <alpine.LFD.2.00.1103151206430.2787@localhost6.localdomain6> <20110315175048.GC24254@linux.vnet.ibm.com>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: owner-linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>, Linux-mm <linux-mm@kvack.org>, Arnaldo Carvalho de Melo <acme@infradead.org>, Linus Torvalds <torvalds@linux-foundation.org>, Ananth N Mavinakayanahalli <ananth@in.ibm.com>, Christoph Hellwig <hch@infradead.org>, Andi Kleen <andi@firstfloor.org>, Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>, Oleg Nesterov <oleg@redhat.com>, LKML <linux-kernel@vger.kernel.org>, Jim Keniston <jkenisto@linux.vnet.ibm.com>, Roland McGrath <roland@hack.frob.com>, SystemTap <systemtap@sources.redhat.com>, Andrew Morton <akpm@linux-foundation.org>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

On Tue, 15 Mar 2011, Srikar Dronamraju wrote:

> * Thomas Gleixner <tglx@linutronix.de> [2011-03-15 14:22:09]:
> 
> > On Mon, 14 Mar 2011, Srikar Dronamraju wrote:
> > > +/*
> > > + * Called with tsk->mm->mmap_sem held (either for read or write and
> > > + * with a reference to tsk->mm
> > 
> > Hmm, why is holding it for read sufficient?
> 
> We are not adding a new vma to the mm; but just replacing a page with
> another after holding the locks for the pages. Existing routines
> doing close to similar things like the
> access_process_vm/get_user_pages seem to be taking the read_lock. Do
> you see a resaon why readlock wouldnt suffice?

No, I just was confused by the comment. Probably should have asked why
you want to call it write locked.
 
Thanks,

	tglx

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>