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Date: Tue, 15 Mar 2011 12:15:30 -0400
From: Stephen Wilson <wilsons@start.ca>
Subject: Re: [PATCH v2 2.6.38-rc8-tip 7/20]  7: uprobes: store/restore
	original instruction.
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To: Steven Rostedt <rostedt@goodmis.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>, Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@elte.hu>, 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, Mar 15, 2011 at 09:47:59AM -0400, Steven Rostedt wrote:
> > 	rcu_read_lock()
> > 	if (mm->owner) {
> > 		get_task_struct(mm->owner)
> > 		tsk = mm->owner;
> > 	}
> > 	rcu_read_unlock()
> > 	if (!tsk)
> > 		return ret;
> > 
> > Agree?
> 
> Or:
> 
> 	rcu_read_lock();
> 	tsk = mm->owner;
> 	if (tsk)
> 		get_task_struct(tsk);
> 	rcu_read_unlock();
> 	if (!tsk)
> 		return ret;
> 
> Probably looks cleaner.

Yes, plus we should do "tsk = rcu_dereference(mm->owner);" and wrap the
whole thing in a static uprobes_get_mm_owner() or similar.


-- 
steve

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