From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EE674C433EF for ; Tue, 7 Sep 2021 20:25:42 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 68AAC61183 for ; Tue, 7 Sep 2021 20:25:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 68AAC61183 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id A60126B0071; Tue, 7 Sep 2021 16:25:41 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A0F0E900002; Tue, 7 Sep 2021 16:25:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 926EE6B0073; Tue, 7 Sep 2021 16:25:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0220.hostedemail.com [216.40.44.220]) by kanga.kvack.org (Postfix) with ESMTP id 84FF56B0071 for ; Tue, 7 Sep 2021 16:25:41 -0400 (EDT) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 40FD11812143B for ; Tue, 7 Sep 2021 20:25:41 +0000 (UTC) X-FDA: 78561908082.09.33533AB Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf11.hostedemail.com (Postfix) with ESMTP id DC24BF000201 for ; Tue, 7 Sep 2021 20:25:40 +0000 (UTC) Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 531E261152; Tue, 7 Sep 2021 20:25:39 +0000 (UTC) Date: Tue, 7 Sep 2021 16:25:37 -0400 From: Steven Rostedt To: Liam Howlett Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Andrew Morton , Michel Lespinasse , Vlastimil Babka , Matthew Wilcox Subject: Re: [PATCH v3] mmap_lock: Change trace and locking order Message-ID: <20210907162537.27cbf082@gandalf.local.home> In-Reply-To: <20210907201456.4036910-1-Liam.Howlett@oracle.com> References: <20210907201456.4036910-1-Liam.Howlett@oracle.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Authentication-Results: imf11.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf11.hostedemail.com: domain of "SRS0=ZahN=N5=goodmis.org=rostedt@kernel.org" designates 198.145.29.99 as permitted sender) smtp.mailfrom="SRS0=ZahN=N5=goodmis.org=rostedt@kernel.org" X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: DC24BF000201 X-Stat-Signature: o7bb5snnbt5smhff5stfao9bm1sgadf6 X-HE-Tag: 1631046340-793422 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, 7 Sep 2021 20:15:19 +0000 Liam Howlett wrote: > The ordering of the printed messages from the mmap_lock trace can occur > out of order. This results in confusing trace logs such as: > > task cpu atomic counter: message > --------------------------------------------- > task-749 [006] .... 14437980: mmap_lock_acquire_returned: mm=00000000c94d28b8 memcg_path= write=true success=true > task-750 [007] .... 14437981: mmap_lock_acquire_returned: mm=00000000c94d28b8 memcg_path= write=true success=true > task-749 [006] .... 14437983: mmap_lock_released: mm=00000000c94d28b8 memcg_path= write=true > > When the actual series of evens are as follows: > > task-749 [006] mmap_lock_acquire_returned: mm=00000000c94d28b8 memcg_path= write=true success=true > task-749 [006] mmap_lock_released: mm=00000000c94d28b8 memcg_path= write=true > > task-750 [007] mmap_lock_acquire_returned: mm=00000000c94d28b8 memcg_path= write=true success=true > > The incorrect ordering of the trace log happens because the release log > is outside of the lock itself. The ordering can be guaranteed by > protecting the acquire success and release trace logs by the lock. > > Signed-off-by: Liam R. Howlett > Suggested-by: Steven Rostedt (VMware) FYI, If you received Acks for a patch, and you resend just to update the change log, you can then include those acks in that email, as the acks were already done for the code change. If you change the code, you may need to ask to get the review/acks again. But since this time you only changed the change log, and the code is still the same, you should have included: Reviewed-by: Matthew Wilcox (Oracle) Reviewed-by: David Hildenbrand Acked-by: Vlastimil Babka -- Steve > --- > include/linux/mmap_lock.h | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h > index 0540f0156f58..b179f1e3541a 100644 > --- a/include/linux/mmap_lock.h > +++ b/include/linux/mmap_lock.h > @@ -101,14 +101,14 @@ static inline bool mmap_write_trylock(struct mm_struct *mm) > > static inline void mmap_write_unlock(struct mm_struct *mm) > { > - up_write(&mm->mmap_lock); > __mmap_lock_trace_released(mm, true); > + up_write(&mm->mmap_lock); > } > > static inline void mmap_write_downgrade(struct mm_struct *mm) > { > - downgrade_write(&mm->mmap_lock); > __mmap_lock_trace_acquire_returned(mm, false, true); > + downgrade_write(&mm->mmap_lock); > } > > static inline void mmap_read_lock(struct mm_struct *mm) > @@ -140,8 +140,8 @@ static inline bool mmap_read_trylock(struct mm_struct *mm) > > static inline void mmap_read_unlock(struct mm_struct *mm) > { > - up_read(&mm->mmap_lock); > __mmap_lock_trace_released(mm, false); > + up_read(&mm->mmap_lock); > } > > static inline bool mmap_read_trylock_non_owner(struct mm_struct *mm) > @@ -155,8 +155,8 @@ static inline bool mmap_read_trylock_non_owner(struct mm_struct *mm) > > static inline void mmap_read_unlock_non_owner(struct mm_struct *mm) > { > - up_read_non_owner(&mm->mmap_lock); > __mmap_lock_trace_released(mm, false); > + up_read_non_owner(&mm->mmap_lock); > } > > static inline void mmap_assert_locked(struct mm_struct *mm)