Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754691AbbBFGrV (ORCPT ); Fri, 6 Feb 2015 01:47:21 -0500 Received: from e23smtp06.au.ibm.com ([202.81.31.148]:42967 "EHLO e23smtp06.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754585AbbBFGrU (ORCPT ); Fri, 6 Feb 2015 01:47:20 -0500 Message-ID: <54D463B6.2020808@linux.vnet.ibm.com> Date: Fri, 06 Feb 2015 12:18:22 +0530 From: Raghavendra K T Organization: IBM User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 MIME-Version: 1.0 To: Linus Torvalds CC: Davidlohr Bueso , Sasha Levin , Waiman Long , Peter Zijlstra , Ingo Molnar , Andrew Morton , Andrey Ryabinin , Dave Jones , LKML Subject: Re: sched: memory corruption on completing completions References: <54D2AA16.6030706@oracle.com> <1423169986.6835.24.camel@stgolabs.net> <54D3DA75.70402@oracle.com> <1423175834.6835.27.camel@stgolabs.net> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15020606-0021-0000-0000-000000C38580 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1214 Lines: 30 On 02/06/2015 04:27 AM, Linus Torvalds wrote: > On Thu, Feb 5, 2015 at 2:37 PM, Davidlohr Bueso wrote: >>> >>> It is possible that the paravirt spinlocks could be saved by: >>> >>> - moving the clearing of TICKET_SLOWPATH_FLAG into the fastpath locking code. >> >> Ouch, to avoid deadlocks they explicitly need the unlock to occur before >> the slowpath tail flag is read. > > Well, just make the unlock do the actual real unlock operation > ("fastpath"), leaving the TICKET_SLOWPATH_FLAG alone. The unlock path > can *test* the flag and do whatever kicking it needs to get people > started again, but not clear it again. > This is definitely a good idea, will think more on this. (especially since any remote possibility of forgetting to wake up the lock-waiter would result in eventual hang of kvm guest). Hopeful to come up with a solution soon. /me agreeing with the fact that we did not have the 'lifetime' in mind during the design :(. -- 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/