From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id 83A666B0286 for ; Fri, 23 Sep 2016 12:06:11 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id 21so232484417pfy.3 for ; Fri, 23 Sep 2016 09:06:11 -0700 (PDT) Received: from mga01.intel.com (mga01.intel.com. [192.55.52.88]) by mx.google.com with ESMTPS id o63si8412329pfi.291.2016.09.23.09.06.10 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 23 Sep 2016 09:06:10 -0700 (PDT) Subject: Re: [PATCH v3 2/2] Documentation/filesystems/proc.txt: Add more description for maps/smaps References: <1474636354-25573-1-git-send-email-robert.hu@intel.com> <1474636354-25573-2-git-send-email-robert.hu@intel.com> From: Dave Hansen Message-ID: <57E552F2.4030302@intel.com> Date: Fri, 23 Sep 2016 09:06:10 -0700 MIME-Version: 1.0 In-Reply-To: <1474636354-25573-2-git-send-email-robert.hu@intel.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Robert Ho , pbonzini@redhat.com, akpm@linux-foundation.org, mhocko@suse.com, oleg@redhat.com, dan.j.williams@intel.com Cc: guangrong.xiao@linux.intel.com, gleb@kernel.org, mtosatti@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, stefanha@redhat.com, yuhuang@redhat.com, linux-mm@kvack.org, ross.zwisler@linux.intel.com On 09/23/2016 06:12 AM, Robert Ho wrote: > +Note: for both /proc/PID/maps and /proc/PID/smaps readings, it's > +possible in race conditions, that the mappings printed may not be that > +up-to-date, because during each read walking, the task's mappings may have > +changed, this typically happens in multithread cases. But anyway in each single > +read these can be guarunteed: 1) the mapped addresses doesn't go backward; 2) no > +overlaps 3) if there is something at a given vaddr during the entirety of the > +life of the smaps/maps walk, there will be some output for it. Could we spuce this description up a bit? Perhaps: Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy. This typically manifests when doing partial reads of these files while the memory map is being modified. Despite the races, we do provide the following guarantees: 1) The mapped addresses never go backwards, which implies no two regions will ever overlap. 2) If there is something at a given vaddr during the entirety of the life of the smaps/maps walk, there will be some output for it. -- 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