linux-kernel - Re: [PATCH v2 2.6.38-rc8-tip 7/20] 7: uprobes: store/restore original instruction.

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Message-ID: <20110315161530.GA23862@fibrous.localdomain>
Date:	Tue, 15 Mar 2011 12:15:30 -0400
From:	Stephen Wilson <wilsons@...rt.ca>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>, Linux-mm <linux-mm@...ck.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Christoph Hellwig <hch@...radead.org>,
	Andi Kleen <andi@...stfloor.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Oleg Nesterov <oleg@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Roland McGrath <roland@...k.frob.com>,
	SystemTap <systemtap@...rces.redhat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2 2.6.38-rc8-tip 7/20]  7: uprobes: store/restore
	original instruction.

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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