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[95.117.56.101]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a01f6c5059sm32619515e9.0.2026.09.30.21.42.16 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 30 Sep 2026 21:42:17 -0700 (PDT) From: Karl Mehltretter To: Vlastimil Babka , Harry Yoo , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Andrew Morton Cc: Karl Mehltretter , Hao Li , Christoph Lameter , David Rientjes , Muchun Song , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , Alexei Starovoitov , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev Subject: [PATCH 1/2] mm/slub: preserve no-lock freeing after memcg charge failure Date: Thu, 1 Oct 2026 06:40:55 +0200 Message-Id: <20261001044056.75079-2-kmehltretter@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <20261001044056.75079-1-kmehltretter@gmail.com> References: <20261001044056.75079-1-kmehltretter@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit kmalloc_nolock() can obtain an object before its memcg post-allocation charge fails. For a single object, memcg_slab_post_alloc_hook() rolls the allocation back through memcg_alloc_abort_single(). That enters the regular SLUB free path, which can take a sleeping list_lock on PREEMPT_RT even though the caller selected a no-lock allocation. Use kfree_nolock() when the allocation flags disallow spinning. This keeps the SLUB object rollback on the no-lock free path. The failed allocation continues to return NULL. Fixes: af92793e52c3 ("slab: Introduce kmalloc_nolock() and kfree_nolock().") Assisted-by: LLM Signed-off-by: Karl Mehltretter --- mm/slub.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/slub.c b/mm/slub.c index 54ec125033571..a1f08338102e2 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2519,7 +2519,10 @@ bool memcg_slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags, return true; if (likely(size == 1)) { - memcg_alloc_abort_single(s, *p); + if (alloc_flags_allow_spinning(ac->alloc_flags)) + memcg_alloc_abort_single(s, *p); + else + kfree_nolock(*p); *p = NULL; } else { kmem_cache_free_bulk(s, size, p); -- 2.53.0