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Thu, 21 Mar 2024 10:48:14 +0800 X-QQ-mid: xmsmtpt1710989294t10a5k7uh Message-ID: X-QQ-XMAILINFO: MyirvGjpKb1jMknYzBTUX1TyLQJJwnGJa2kGkEXkzy0QynM54t99hdlGOmruc7 toQQcHl+vKWX9+9pLw9QmAfPfFz+Fcina/RUynC85MoalhWZJrTyu6CyQqCS0xH5CKDvha3pOLwj 8dDw9JGPUmWO2qXBykbYrODaauNVGyEaclEu/d9oiQqBLlEphq2aUQ9NVG80sufxqxP0G4D1v40C tQrqGcv4HO84B8O1I9YRrb1N3nj8uhY/YUFSsDGuNjo+m+Iq6xElACW21mDdJfUEroXSciS2ixUN H+rKWbQVORslYyIKY1A6Q6Fxfu89FN5Ryp2yashaiCveCtW5/vHG4ws+bUdE2VbiuX7bsrl/wO+C MpP3YdXcBydST3g32C7EOvTw1Kd1nOBvWvtVxYe0PZ9uEnloRdGNed/Mct8rEEQO500MQGqrP5rX VIMPgJZkFwZLA4O3cL24DYJFCLY4GPj1f3Ixj6mLoAdjQ8XwGyjCexj1uBEpztO8HBHORuKyp2BI aVwZt2J71jdknC5+W9ADQnPVjSFR3m41sCVIAorqC7MTXdbStHbQTFg2UtFIU6fmRSaQOqKZWcTF VfEgnKXWsvjhm7uZww+85MWGqikf4OL34cqXdxy1T/FtwBxJOlwQi80Hq+LNuCkvmsDHmaUNNjWh we4l0y3SE2ZGahL/SFY+rG/UBILx17k8CLnSWqZBcXpy3PnmLHar5/5IK5El4+xLj46Bp8f0GpQO eOD3J3SAweSh+8+DyG1ztLSPP6Q8bOuFspz1jA4z+YVsYw7WVk062wkCSYmu/RTpff455UuvskHK MaEJm6sLtRYa0M3Y9VT4utfv54gnO8frSX5gCLEcO273dAgfO/cN7cFQlByVr8hhkNX+N5R0sHTU dpICBgdQ6Yx7U/yMBshA8ulpDLrGTFAv0dgpHdAAJBemTATMJrF7mZipsHDLAemsXeM0Y9TFBGFv /f5FTsnAEHHEYplPbe+ABftfReiA1wd2uhHnjKcshWTx6du94nyusaSVT9N7IvTj/rxsj61DELwe wz83YKpm0UjRl3oTXu X-QQ-XMRINFO: MSVp+SPm3vtS1Vd6Y4Mggwc= From: linke li To: chengming.zhou@linux.dev Cc: 42.hyeyoo@gmail.com, akpm@linux-foundation.org, cl@linux.com, iamjoonsoo.kim@lge.com, lilinke99@qq.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, penberg@kernel.org, rientjes@google.com, roman.gushchin@linux.dev, vbabka@suse.cz Subject: Re: [PATCH] mm/slub: mark racy accesses on slab->slabs Date: Thu, 21 Mar 2024 10:48:11 +0800 X-OQ-MSGID: <20240321024811.57550-1-lilinke99@qq.com> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: <8bc1aebf-8395-416f-8c23-53cbd25d0eef@linux.dev> References: <8bc1aebf-8395-416f-8c23-53cbd25d0eef@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 60FD11C0002 X-Rspam-User: X-Stat-Signature: ort98ryrnzgrke1etse968ymkafugpgw X-Rspamd-Server: rspam03 X-HE-Tag: 1710989319-276077 X-HE-Meta: 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 QweYUZW7 vSChOs7cyiMrhp2z9+HHt7kTiGRwcmbWHMe5McwUm9ZvCriugSzfdjxSRiZqCUciaC81+tKUYyxzhfrh3fdeAbxDH3e6GSYEmiLkpSHx87UYadPgM3u97VLjx7s6CFzkRqCN82iiYkD4n1hIGC5Ref89ZoC+4Lb6b/28l3901irf73FNS4D5VxFd5AEX6DcD6XvRTypVc0dQdkrOmr4u/7DNgPNzbGMUR8ayRByyrKvhG5zIK5HOeSOvgb5YsAEUXYJg2ESlRj9BHhIDWLAWfZv6gTelVbdbddJJQWB3n1xIQCnUdbTeyijPxjeYiERkHm7EboQr21pz+1ZSu37mRT7v92w== X-Bogosity: Ham, tests=bogofilter, spamicity=0.024587, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Sorry for a late reply, I just found this because of my bad email client. > There is another unmarked access of "slab->slabs" in the show_slab_objects(), > which you can change too. Yes, I think show_slab_objects() has a similar situation. Should I consider to submit a V2 patch for this? > I'm not sure that it's really safe to access "slab->slabs" here without any protection? > Although it should be no problem in practice, alternative choice maybe putting partial > slabs count in the kmem_cache_cpu struct. I think it is ok, because it seems that slab->slabs in slub_percpu_partial and show_slab_objects() are just used for showing some infomation. I noticed Paul summarized some of these strategies in access-marking.txt[1] Quote from it: "Use of the data_race() Macro ---------------------------- Here are some situations where data_race() should be used instead of READ_ONCE() and WRITE_ONCE(): 1. Data-racy loads from shared variables whose values are used only for diagnostic purposes. 2. Data-racy reads whose values are checked against marked reload. 3. Reads whose values feed into error-tolerant heuristics. 4. Writes setting values that feed into error-tolerant heuristics. " Thanks, Linke [1]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/memory-model/Documentation/access-marking.txt