Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755706AbZDPV1u (ORCPT ); Thu, 16 Apr 2009 17:27:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752334AbZDPV1l (ORCPT ); Thu, 16 Apr 2009 17:27:41 -0400 Received: from cantor.suse.de ([195.135.220.2]:50035 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752092AbZDPV1k (ORCPT ); Thu, 16 Apr 2009 17:27:40 -0400 Date: Thu, 16 Apr 2009 14:24:36 -0700 From: Greg KH To: Hugh Dickins Cc: Linus Torvalds , Tetsuo Handa , arjan@linux.intel.com, alan@lxorguk.ukuu.org.uk, viro@ZenIV.linux.org.uk, jmorris@namei.org, akpm@linux-foundation.org, paulmck@linux.vnet.ibm.com, linux-kernel@vger.kernel.org Subject: Re: Please revert kobject_uevent UMH_NO_WAIT Message-ID: <20090416212436.GA31113@suse.de> References: <20090410231245.GF6719@linux.vnet.ibm.com> <20090410233919.GS26366@ZenIV.linux.org.uk> <200904130048.n3D0mw1f077050@www262.sakura.ne.jp> <200904150328.n3F3S0F9083222@www262.sakura.ne.jp> <200904160046.n3G0ki9o028612@www262.sakura.ne.jp> <200904160535.n3G5ZBIE006724@www262.sakura.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1663 Lines: 40 On Thu, Apr 16, 2009 at 09:55:29PM +0100, Hugh Dickins wrote: > Please revert commit f520360d93cdc37de5d972dac4bf3bdef6a7f6a7 > "kobject: don't block for each kobject_uevent". > > Tetsuo Handa, running a kernel with CONFIG_DEBUG_PAGEALLOC=y > and CONFIG_UEVENT_HELPER_PATH=/sbin/hotplug, has been hitting RCU > detected CPU stalls: it's been spinning in the loop where do_execve() > counts up the args (but why wasn't fixup_exception working? dunno). > > The recent change, switching kobject_uevent_env() from UMH_WAIT_EXEC > to UMH_NO_WAIT, is broken: the exec uses args on the local stack here, > and an env which is kfreed as soon as call_usermodehelper() returns. > It very much needs to wait for the exec to be done. > > Or keep the UMH_NO_WAIT, and complicate the code to allocate and free > these resources correctly? No, as GregKH pointed out when making the > commit, CONFIG_UEVENT_HELPER_PATH="" is a much better optimization - > though some distros are still saying /sbin/hotplug in their .config, > yet with no such binary in their initrd or their root. > > Or... > > [PATCH] revert kobject_uevent UMH_NO_WAIT > > Reported-by: Tetsuo Handa > Signed-off-by: Hugh Dickins Acked-by: Greg Kroah-Hartman Linus, I can do this in a tree of patches to send to you or you can do it yourself, which ever is easier. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/