From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f69.google.com (mail-it0-f69.google.com [209.85.214.69]) by kanga.kvack.org (Postfix) with ESMTP id 4A89C6B0311 for ; Tue, 6 Jun 2017 22:21:16 -0400 (EDT) Received: by mail-it0-f69.google.com with SMTP id 185so964155itv.8 for ; Tue, 06 Jun 2017 19:21:16 -0700 (PDT) Received: from szxga03-in.huawei.com (szxga03-in.huawei.com. [45.249.212.189]) by mx.google.com with ESMTPS id o79si324584iod.158.2017.06.06.19.21.14 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 06 Jun 2017 19:21:15 -0700 (PDT) Message-ID: <593762FF.10705@huawei.com> Date: Wed, 7 Jun 2017 10:20:47 +0800 From: zhong jiang MIME-Version: 1.0 Subject: Re: double call identical release when there is a race hitting References: <5936B098.6020807@huawei.com> <20170606155600.GA17705@redhat.com> In-Reply-To: <20170606155600.GA17705@redhat.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Oleg Nesterov Cc: Michal Hocko , Vlastimil Babka , David Rientjes , Hugh Dickins , Linux Memory Management List , LKML , Xishi Qiu On 2017/6/6 23:56, Oleg Nesterov wrote: > I can't answer authoritatively, but > > On 06/06, zhong jiang wrote: >> Hi >> >> when I review the code, I find the following scenario will lead to a race , >> but I am not sure whether the real issue will hit or not. >> >> cpu1 cpu2 >> exit_mmap mmu_notifier_unregister >> __mmu_notifier_release srcu_read_lock >> srcu_read_lock >> mm->ops->release(mn, mm) mm->ops->release(mn,mm) >> srcu_read_unlock srcu_read_unlock >> >> >> obviously, the specified mm will call identical release function when >> the related condition satisfy. is it right? > I think you are right, this is possible, perhaps the comments should mention > this explicitly. > > See the changelog in d34883d4e35c0a994e91dd847a82b4c9e0c31d83 "mm: mmu_notifier: > re-fix freed page still mapped in secondary MMU": > > "multiple ->release() callouts", we needn't care it too much ... > > Oleg. > > > . > Thank you for clarification. yes, I see that the author admit that this is a issue. The patch describe that it is really rare. Anyway, this issue should be fixed in a separate patch. but so far the issue still exist unfortunately. Regards zhongjiang -- 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/ . Don't email: email@kvack.org