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([2405:4802:21dc:72d0:a033:17f7:ad44:4f35]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3990c40d0c9sm311768a91.7.2026.08.31.09.24.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 31 Aug 2026 09:24:49 -0700 (PDT) From: ThangNN99 To: Vlastimil Babka Cc: Harry Yoo , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , Andrew Morton , Peter Zijlstra , Alexei Starovoitov , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, ThangNN99 Subject: Re: [PATCH] mm/slab: disallow kfree_rcu_sheaf() on PREEMPT_RT again Date: Mon, 31 Aug 2026 23:24:42 +0700 Message-ID: <20260831162442.8176-1-ngocthang2710.1999@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260831-b4-kfree_rcu_hotfix-v1-1-4f0fb882638b@kernel.org> References: <20260831-b4-kfree_rcu_hotfix-v1-1-4f0fb882638b@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Thanks Vlastimil, this matches what I found and is functionally the same fix I had in my v3. I built this exact logic (skip kfree_rcu_sheaf() under CONFIG_PREEMPT_RT in kvfree_call_rcu(), same dead-code removal in kfree_rcu_sheaf()) against commit 08dbfad3f504 with the syzbot .config and reproduced the original splat with syzbot's C repro (writing "off" to /sys/devices/system/cpu/smt/control to trigger the __balance_push_cpu_stop -> select_fallback_rq -> cpuset_cpus_allowed_fallback -> set_cpus_allowed_force -> kvfree_call_rcu chain) — confirmed the exact same lockdep report as syzbot, then rebuilt with the fix and confirmed the splat no longer appears while the same code path still executes. Feel free to add: Tested-by: ThangNN99 Thanks for picking this up and for the pi_lock/waitlock explanation, that's a much more precise description than what I had. ThangNN99