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Wed, 04 Nov 2026 08:46:28 -0800 (PST) Received: from localhost ([153.61.198.251]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ed08bd4a3csm9983805ad.11.2026.11.04.08.46.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Nov 2026 08:46:27 -0800 (PST) Content-Type: text/plain; charset=UTF-8 Date: Wed, 04 Nov 2026 16:46:26 +0000 Message-Id: Subject: Re: [PATCH for-next-fixes v2 4/5] mm/slab: fix a deadlock in memcg_alloc_abort_single() From: "Alexei Starovoitov" To: "Vlastimil Babka (SUSE)" , "Harry Yoo" Cc: "Johannes Weiner" , "Michal Hocko" , "Roman Gushchin" , "Shakeel Butt" , "Muchun Song" , "Andrew Morton" , "Hao Li" , "Christoph Lameter" , "David Rientjes" , "Sebastian Andrzej Siewior" , "Clark Williams" , "Steven Rostedt" , , , , , , "Sashiko" In-Reply-To: <6441429b-eff2-485b-acf3-26c3034910ae@kernel.org> References: <20261103-kmalloc-nolock-fixes-v2-0-19167cfe4779@kernel.org> <20261103-kmalloc-nolock-fixes-v2-4-19167cfe4779@kernel.org> <6441429b-eff2-485b-acf3-26c3034910ae@kernel.org> Content-Transfer-Encoding: 8bit X-Mailing-List: linux-rt-devel@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 On Wed, Nov 04, 2026 at 07:35 AM Vlastimil Babka (SUSE) wrote: >> 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); > > Why not try free_to_pcs with allow_spin as well then, and improve > memcg_alloc_abort_single() for both contexts? yep. Even better. The bulk side does that already. Like: if (likely(can_free_to_pcs(slab)) && likely(free_to_pcs(s, object, allow_spin))) return; if (likely(allow_spin)) __slab_free(s, slab, object, object, 1, _RET_IP_); else defer_free(s, object); ?