From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id 9F7086B0011 for ; Wed, 27 Apr 2011 20:32:14 -0400 (EDT) Received: from d01relay03.pok.ibm.com (d01relay03.pok.ibm.com [9.56.227.235]) by e1.ny.us.ibm.com (8.14.4/8.13.1) with ESMTP id p3S0LPNR010930 for ; Wed, 27 Apr 2011 20:21:25 -0400 Received: from d01av01.pok.ibm.com (d01av01.pok.ibm.com [9.56.224.215]) by d01relay03.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p3S0WD0p095102 for ; Wed, 27 Apr 2011 20:32:13 -0400 Received: from d01av01.pok.ibm.com (loopback [127.0.0.1]) by d01av01.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p3S0WCpu007247 for ; Wed, 27 Apr 2011 20:32:13 -0400 Subject: Re: [PATCH 1/2] break out page allocation warning code From: john stultz In-Reply-To: References: <1303331695.2796.159.camel@work-vm> <20110421103009.731B.A69D9226@jp.fujitsu.com> <1303846026.2816.117.camel@work-vm> Content-Type: text/plain; charset="UTF-8" Date: Wed, 27 Apr 2011 17:32:08 -0700 Message-ID: <1303950728.2971.35.camel@work-vm> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: KOSAKI Motohiro , Dave Hansen , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Johannes Weiner , Michal Nazarewicz , Andrew Morton On Wed, 2011-04-27 at 16:51 -0700, David Rientjes wrote: > On Tue, 26 Apr 2011, john stultz wrote: > > In the meantime, I'll put some effort into trying to protect unlocked > > current->comm acccess using get_task_comm() where possible. Won't happen > > in a day, and help would be appreciated. > > > > We need to stop protecting ->comm with ->alloc_lock since it is used for > other members of task_struct that may or may not be held in a function > that wants to read ->comm. We should probably introduce a seqlock. Agreed. My initial approach is to consolidate accesses to use get_task_comm(), with special case to skip the locking if tsk==current, as well as a lock free __get_task_comm() for cases where its not current being accessed and the task locking is already done. Once that's all done, the next step is to switch to a seqlock (or possibly RCU if Dave is still playing with that idea), internally in the get_task_comm implementation and then yank the special __get_task_comm. But other suggestions are welcome. thanks -john -- 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: email@kvack.org