From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S933211Ab1JGRII (ORCPT <rfc822;w@1wt.eu>);
	Fri, 7 Oct 2011 13:08:08 -0400
Received: from mx1.redhat.com ([209.132.183.28]:20426 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1753538Ab1JGRIG (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Fri, 7 Oct 2011 13:08:06 -0400
Date: Fri, 7 Oct 2011 19:03:47 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>, 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>, Hugh Dickins <hughd@google.com>,
        Christoph Hellwig <hch@infradead.org>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        Thomas Gleixner <tglx@linutronix.de>, Andi Kleen <andi@firstfloor.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Jim Keniston <jkenisto@linux.vnet.ibm.com>,
        Roland McGrath <roland@hack.frob.com>,
        Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v5 3.1.0-rc4-tip 3/26]   Uprobes: register/unregister
	probes.
Message-ID: <20111007170347.GB32319@redhat.com>
References: <20110920115938.25326.93059.sendpatchset@srdronam.in.ibm.com> <20110920120022.25326.35868.sendpatchset@srdronam.in.ibm.com> <20111003124640.GA25811@redhat.com> <20111005170420.GB28250@linux.vnet.ibm.com> <20111005185008.GA8107@redhat.com> <20111006065125.GC17591@linux.vnet.ibm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20111006065125.GC17591@linux.vnet.ibm.com>
User-Agent: Mutt/1.5.18 (2008-05-17)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 10/06, Srikar Dronamraju wrote:
>
> * Oleg Nesterov <oleg@redhat.com> [2011-10-05 20:50:08]:
>
> yes we might be doing an unnecessary __register_uprobe() but because it
> raced with unregister_uprobe() and got the lock, we would avoid doing a
> __unregister_uprobe().
>
> However I am okay to move the lock before del_consumer().

To me this looks a bit "safer" even if currently __register is idempotent.

But,

> Please let me
> know how you prefer this.

No, no, Srikar. Please do what you prefer. You are the author.

And btw I forgot to mention that initially I wrongly thought this is buggy.

Oleg.