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Tue, 03 Nov 2026 13:11:04 -0800 (PST) Received: from localhost ([153.61.198.252]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3b0944ee6easm336849a91.2.2026.11.03.13.11.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Nov 2026 13:11:04 -0800 (PST) Content-Type: text/plain; charset=UTF-8 Date: Tue, 03 Nov 2026 21:11:03 +0000 Message-Id: Cc: "Johannes Weiner" , "Michal Hocko" , "Roman Gushchin" , "Shakeel Butt" , "Muchun Song" , "Andrew Morton" , "Vlastimil Babka" , "Hao Li" , "Christoph Lameter" , "David Rientjes" , "Sebastian Andrzej Siewior" , "Clark Williams" , "Steven Rostedt" , , , , , , "Sashiko" Subject: Re: [PATCH for-next-fixes v2 4/5] mm/slab: fix a deadlock in memcg_alloc_abort_single() From: "Alexei Starovoitov" To: "Harry Yoo" In-Reply-To: References: <20261103-kmalloc-nolock-fixes-v2-0-19167cfe4779@kernel.org> <20261103-kmalloc-nolock-fixes-v2-4-19167cfe4779@kernel.org> Content-Transfer-Encoding: 8bit X-Archived-By: MIME-Version: 1.0 X-Stat-Signature: qjnccfh31eo3hsteq3kmbrr3in7adf3a X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 4771420002 X-Spam-Status: No, score=-2.8 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 autolearn=no autolearn_force=no version=4.0.1 X-HE-Tag: 1793740266-799628 X-HE-Meta: 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 pQKY9x2d 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 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 Tue, Nov 03, 2026 at 12:21 PM Harry Yoo wrote: > While this is technically true, this relies too much on the current > implementation details and makes the code hard to follow. Fair enough. I don't insist. > Patch 2 is an independent bugfix as-is already. We should really stop > open-coding slab_free_hook(). That ended up missing init_on_free handing. Right. No objection to patch 2. With patches 2 and 3 the !allow_spin side of memcg_alloc_abort_single() is an open coded kfree_nolock(): kfree_nolock() memcg_alloc_abort_single(!allow_spin) -------------------------------- ------------------------------------- memcg_slab_free_hook() - alloc_tagging_slab_free_hook() alloc_tagging_slab_free_hook() slab_free_hook(!allow_spin) slab_free_hook(!allow_spin) free_to_pcs() - defer_free() defer_free() I don't insist on kfree_nolock() there, but can we try free_to_pcs() before defer_free() ? Like: if (likely(allow_spin)) __slab_free(s, slab, object, object, 1, _RET_IP_); else if (!can_free_to_pcs(slab) || !free_to_pcs(s, object, false)) defer_free(s, object);