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

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Message-ID: <1300196879.9910.271.camel@gandalf.stny.rr.com>
Date:	Tue, 15 Mar 2011 09:47:59 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Stephen Wilson <wilsons@...rt.ca>,
	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, 2011-03-15 at 14:52 +0530, Srikar Dronamraju wrote:
> * Stephen Wilson <wilsons@...rt.ca> [2011-03-14 14:09:14]:
> 

Nitpick:

> Guess checking for tsk != NULL would only help if and only if we are doing
> within rcu.  i.e we have to change to something like this
> 

	tsk = NULL;

> 	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.

-- Steve


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