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([2001:9e8:f133:a901:840b:2bf2:919c:cec5]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4601f2f5612sm22213455f8f.15.2026.06.05.00.12.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 05 Jun 2026 00:12:10 -0700 (PDT) Message-ID: <02b1e77e-5b7e-41cb-95b6-731ed00d9e74@gmail.com> Date: Fri, 5 Jun 2026 09:12:09 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] MIPS: smp: report dying CPU to RCU in stop_this_cpu() Content-Language: en-US To: Sebastian Andrzej Siewior Cc: Thomas Bogendoerfer , linux-mips@vger.kernel.org, Clark Williams , Steven Rostedt , Thomas Gleixner , Jiayuan Chen , linux-rt-devel@lists.linux.dev, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260604182407.3109536-1-jelonek.jonas@gmail.com> <20260605064250.q0aRKkon@linutronix.de> From: Jonas Jelonek In-Reply-To: <20260605064250.q0aRKkon@linutronix.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Sebastian, I'm not an expert in this area so please correct me if some claim or explanation is wrong. On 05.06.26 08:42, Sebastian Andrzej Siewior wrote: > On 2026-06-04 18:24:07 [+0000], Jonas Jelonek wrote: > … >> This issue popped up during kernel bump downstream in OpenWrt from >> 6.18.33 to 6.18.34, since the suspected change has been backported to >> 6.18 stable branch [1]. > I would avoid the link and simply write after the backport of the patch > or so. Fine with that, I can adjust that in a v2. >> Call rcutree_report_cpu_dead() once interrupts are disabled, mirroring the >> generic CPU-hotplug offline path (and arm64's stop handling), so RCU stops >> waiting on the parked CPUs and grace periods can still complete. > This is part of cpuhp_report_idle_dead(). Is it now invoked twice? Or is > something else missing/ different? Those seem to be two different paths. To be honest I'm not confident under which circumstances which of those paths is used to take down a CPU. In my case, issuing a reboot command reaches smp_send_stop() where the issue explained in the patch message then happens. > Sebastian Best, Jonas