Subject: Re: [PATCH v2 2.6.38-rc8-tip 7/20]  7: uprobes: store/restore
 original instruction.
From: Peter Zijlstra <peterz@infradead.org>
To: balbir@linux.vnet.ibm.com
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
        Stephen Wilson <wilsons@start.ca>, 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>
In-Reply-To: <20110315185841.GH3410@balbir.in.ibm.com>
References: <20110314133403.27435.7901.sendpatchset@localhost6.localdomain6>
	 <20110314133522.27435.45121.sendpatchset@localhost6.localdomain6>
	 <20110314180914.GA18855@fibrous.localdomain>
	 <20110315092247.GW24254@linux.vnet.ibm.com>
	 <1300211862.2203.302.camel@twins> <20110315185841.GH3410@balbir.in.ibm.com>
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Date: Tue, 15 Mar 2011 20:30:32 +0100
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On Wed, 2011-03-16 at 00:28 +0530, Balbir Singh wrote:
> 
> mm->owner should be under rcu_read_lock, unless the task is exiting
> and mm_count is 1. mm->owner is updated under task_lock().
> 
> > Also, the assignments in kernel/fork.c and kernel/exit.c don't use
> > rcu_assign_pointer() and therefore lack the needed write barrier.
> >
> 
> Those are paths when the only context using the mm->owner is single
>  
> > Git blames Balbir for this.
> 
> I accept the blame and am willing to fix anything incorrect found in
> the code. 

:-), ok sounds right, just wasn't entirely obvious when having a quick
look.

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