From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <owner-linux-mm@kvack.org>
Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35])
	by kanga.kvack.org (Postfix) with ESMTP id 66F2D8D003B
	for <linux-mm@kvack.org>; Thu, 21 Apr 2011 13:39:06 -0400 (EDT)
Received: from j77219.upc-j.chello.nl ([24.132.77.219] helo=dyad.programming.kicks-ass.net)
	by casper.infradead.org with esmtpsa (Exim 4.72 #1 (Red Hat Linux))
	id 1QCxqM-0008Uj-I8
	for linux-mm@kvack.org; Thu, 21 Apr 2011 17:39:06 +0000
Subject: Re: [PATCH v3 2.6.39-rc1-tip 15/26] 15: uprobes: Handing int3 and
 singlestep exception.
From: Peter Zijlstra <peterz@infradead.org>
In-Reply-To: <20110421171042.GI10698@linux.vnet.ibm.com>
References: 
	 <20110401143223.15455.19844.sendpatchset@localhost6.localdomain6>
	 <20110401143527.15455.32854.sendpatchset@localhost6.localdomain6>
	 <1303218185.8345.0.camel@twins> <20110421171042.GI10698@linux.vnet.ibm.com>
Content-Type: text/plain; charset="UTF-8"
Date: Thu, 21 Apr 2011 19:41:38 +0200
Message-ID: <1303407698.2035.159.camel@laptop>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: owner-linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: 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>, Jonathan Corbet <corbet@lwn.net>, Christoph Hellwig <hch@infradead.org>, Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>, Thomas Gleixner <tglx@linutronix.de>, Ananth N Mavinakayanahalli <ananth@in.ibm.com>, Oleg Nesterov <oleg@redhat.com>, LKML <linux-kernel@vger.kernel.org>, SystemTap <systemtap@sources.redhat.com>, Jim Keniston <jkenisto@linux.vnet.ibm.com>, Roland McGrath <roland@hack.frob.com>, Andi Kleen <andi@firstfloor.org>, Andrew Morton <akpm@linux-foundation.org>

On Thu, 2011-04-21 at 22:40 +0530, Srikar Dronamraju wrote:
> * Peter Zijlstra <peterz@infradead.org> [2011-04-19 15:03:05]:
> 
> > On Fri, 2011-04-01 at 20:05 +0530, Srikar Dronamraju wrote:
> > > +       if (unlikely(!utask)) {
> > > +               utask = add_utask();
> > > +
> > > +               /* Failed to allocate utask for the current task. */
> > > +               BUG_ON(!utask);
> > 
> > That's not really nice is it ;-) means I can make the kernel go BUG by
> > simply applying memory pressure.
> > 
> 
> The other option would be remove the probe and set the ip to
> the breakpoint address and restart the thread.

While its better than GFP_NOFAIL since its a return to userspace and
hence cannot be holding locks etc.. it's still not pretty. But heaps
better than simply bailing the kernel.



--
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>