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Sat, 09 Mar 2024 15:56:57 +0800 X-QQ-mid: xmsmtpt1709971017tf0kf6ubj Message-ID: X-QQ-XMAILINFO: MIAHdi1iQo+zZ0BjCihli4BE3n5peZ8ehZdgt+CX+t6VAX7Vg4DYl3oLjf9ily cxzVXzLazy0ntdTUjO3IosXsJPIv8Lp8GHaaXRi8Wv5sa12GdzfOF16WV75+bASzw0mCA0XH3MfI whHosZOMB/RNG6n7bEk/SjQzq4NyoQ1ub0wuEW4hm0RECzeSv3RcDmI6vcapP1zJvo3qBsdZb7DG lOFakRUUn8bSxepyq7BKDYDTY2cQKE2eWoeW67QlMtc93Vdt6GdY257/kGeFj6lOuPFK/tbYaRk3 /dF3DUXG2aj3vDoRnpwW0RfRZ2XqeTgZa25L1g40nvZNRZOEoTEyeoGY0WM/hOzjGeP/M4LMZ8oG 3dTa7Q4i5ElDBsNo3JVKcomIX/3GSZ+PsDIoQ7dR6xOr78IMPoQ5ZdwnSMIZ9qG34W05uBEihnBl okU0zy8PMrVuXUUY/yULRmJdN9UPu+C399H1rR7/bYDmM9CdXdVqDpn7Zs1aPvIeTWC6ldTGoo7A jdbYjW80j79dfT/XiBUiNjPXWznOE241ihSj9Mgxu/f8yiVAYj3v5fLzsMIr6cuPE45gG9ESf+UL QDkqY5ntkHc2Ab1vhlNePtfgoJtCmHDOcrA+VlM2szfR1uUzakfJ0V5l4GJYybtZRa8eHDPz1E9G nAkine/urV8nIBjNAg/95ItzcBi9ImZpCcF+0jnYYrDeC0MVXLiJm9ZnJds3kIb4XQrJlewGEwt7 SiWMEldGn3LsT+zuipKk0ZLeE99c//WiAWQpborqHpm0X43E1TQSWXrtTA2f232YY5FR2P2S4Rtf V6Nmlo9usZJkZBOEKFHFMTyl1E4euuIj2Rc6r1GClJvaGSaFxVVOWcJ4kwLcKKKwlNwak6eiWKbF 995H7SDjf5aUnoXcd2Dg1Gra3IRNJ0flZK3C4PQftf5bMJdAi2Mp7vRzHSnE1Ba89Ujlnqk2uNN5 UEMgzhTIx3Ae9xLkl62rI4M12AcgLKnianHdYulybaA9ydK9yq4m0QitR69fZoIhkST04cGX0/WN 9cNUdtjPWBnQiHRD2dizb8qUUTUA4= X-QQ-XMRINFO: OWPUhxQsoeAVDbp3OJHYyFg= From: linke li To: Cc: lilinke99@qq.com, Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH] mm/slub: mark racy accesses on slab->slabs Date: Sat, 9 Mar 2024 15:48:56 +0800 X-OQ-MSGID: <20240309074856.49648-1-lilinke99@qq.com> X-Mailer: git-send-email 2.39.3 (Apple Git-146) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 3BA1E120006 X-Stat-Signature: pbhraa4s6gw1wgwhte6qhxj116zddzk1 X-HE-Tag: 1709971045-848110 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.001076, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The reads of slab->slabs are racy because it may be changed by put_cpu_partial concurrently. And in slabs_cpu_partial_show ->slabs is only used for output. Data-racy reads from shared variables that are used only for diagnostic purposes should typically use data_race(), since it is normally not a problem if the values are off by a little. This patch is aimed at reducing the number of benign races reported by KCSAN in order to focus future debugging effort on harmful races. Signed-off-by: linke li --- mm/slub.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 2ef88bbf56a3..7b20591e7f8a 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -6257,7 +6257,7 @@ static ssize_t slabs_cpu_partial_show(struct kmem_cache *s, char *buf) slab = slub_percpu_partial(per_cpu_ptr(s->cpu_slab, cpu)); if (slab) - slabs += slab->slabs; + slabs += data_race(slab->slabs); } #endif @@ -6271,7 +6271,7 @@ static ssize_t slabs_cpu_partial_show(struct kmem_cache *s, char *buf) slab = slub_percpu_partial(per_cpu_ptr(s->cpu_slab, cpu)); if (slab) { - slabs = READ_ONCE(slab->slabs); + slabs = data_race(slab->slabs); objects = (slabs * oo_objects(s->oo)) / 2; len += sysfs_emit_at(buf, len, " C%d=%d(%d)", cpu, objects, slabs); -- 2.39.3 (Apple Git-146)