From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753134Ab1C2NJB (ORCPT ); Tue, 29 Mar 2011 09:09:01 -0400 Received: from mail-fx0-f46.google.com ([209.85.161.46]:46825 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752680Ab1C2NJA (ORCPT ); Tue, 29 Mar 2011 09:09:00 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:date:from:to:cc:subject:message-id:mime-version:content-type :content-disposition:user-agent; b=Z7DceVgYVvF4YbhuLp3AwAC9VpizYS/Pw9lqDw/EN2hmVMhdHlrbE3JanF9w2K6FsP KwlrFVXIVZdQ9yGUzCRqcFs9OlIa6PEIqZc5fLgXbYcxJxekoVVudYbx8AkzSgQzoUXG meqo1ahujE+NgKLeUj3Kz9PFA/DHeX3+nY9kM= Date: Tue, 29 Mar 2011 15:08:55 +0200 From: Tejun Heo To: trenn@novell.com, suresh.b.siddha@intel.com Cc: linux-kernel@vger.kernel.org Subject: stop_con_cpu_nowait() usage in set_mtrr() Message-ID: <20110329130855.GA16492@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Suresh, Thomas. This is about the openSUSE complete system freeze at start bug Thomas just pinged about - https://bugzilla.novell.com/show_bug.cgi?id=672008 I looked through the set_mtrr() code and it's implementing its own stop_machine() using stop_one_cpu_nowait(). This isn't safe. There is only one stop cpu execution context per cpu and the custom implementation can race against the standard stop_machine() - it can deadlock with each holding some of the execution contexts and neither stepping away. Suresh, is there any reason why set_mtrr() is using its own synchronization instead of stop_machine()? Thanks. -- tejun