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Wed, 04 Nov 2026 02:07:24 -0800 (PST) Received: from lima-ubuntu.hz.ali.com ([47.246.98.214]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ed08fe55c8sm5603145ad.14.2026.11.04.02.07.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Nov 2026 02:07:24 -0800 (PST) From: Qing Wang To: xuhx@hust.edu.cn, Vlastimil Babka , Harry Yoo , Andrew Morton , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: mm/slub: has_pcs_used() reads remote per-CPU sheaf state from flush_all_cpus_locked() without synchronization (data race; KCSAN blind spot: slub.o is uninstrumented) Date: Wed, 4 Nov 2026 18:07:17 +0800 Message-Id: <20261104100717.2666250-1-wangqing7171@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20261104094132.2665206-1-wangqing7171@gmail.com> References: <20261104094132.2665206-1-wangqing7171@gmail.com> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=no autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam09 X-Stat-Signature: mng4eee3qayo3t5kmkygbrdiznwgbmc8 X-Rspamd-Queue-Id: E233440004 X-Rspam-User: X-HE-Tag: 1793786845-741637 X-HE-Meta: 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 UOXCZ1cE eX4El5SZl1RAz6+/ULg3C5r/T2EVaBExv4rOTQXHOiVop0wNI2Ax5snOuRGbukn+QWd/k/DvjNzcmFSvi5GoVsBcJjWD+neYLHc4/sS0YmQsNnnEs5JHaoX/bxx5dyjSkYvyS3KCqev3GKw77kypdBb9PcuBGT1UeLs0UngoXVqaBa1u9gfkjez8G3nKUXNKUoE/LFzj3A9XFUM6h353WCC5jTfOqDrwj7RCcSsiPbEYpBGUQNJKLfJnk0JmHjZcypWb+lhc3lOyV9W8KHQvh6u2FVFr3YZiVTfSMWzEhRWv3CRpDENtYKs8QMZD9yYFdMJVXbebFuIv1naUIAITdVt3B9n0JnVuOdsZJHG854r7pbb2cHc7KtkbJxPz+EBAld6DLy59oY+jYp25UJ8T/AmE5Jo+eFz9ncBx9Irl4g6NvLjKZPU+nw6v/k37ENEZhsW78uYzyNYk65Ck= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Wed, 04 Nov 2026 at 17:41, Qing Wang wrote: > You're right, there is a data race in has_pcs_used() reading the pcs > fields. The possible consequences: > > 1. has_pcs_used() observes an empty pcs and sets sfw->skip, so the > flush is skipped and the memory is not freed in time. Sorry, I didn't state point 1 correctly. It should be: has_pcs_used() reads main->size as 0 before the concurrent free increments it, so sfw->skip is wrongly set and the memory is not reclaimed in time. -- Best regards, Qing