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[59.124.168.89]) by smtp.gmail.com with ESMTPSA id d12-20020a170902cecc00b001d92db44c9bsm2346896plg.17.2024.01.31.22.25.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 31 Jan 2024 22:25:07 -0800 (PST) From: Andy Chiu To: rostedt@goodmis.org, linux-trace-kernel@vger.kernel.org Cc: bristot@kernel.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, Andy Chiu Subject: [v1] trace/hwlat: stop worker if !is_percpu_thread due to hotplug event Date: Thu, 1 Feb 2024 14:24:55 +0800 Message-ID: <20240201062455.3154803-1-andy.chiu@sifive.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit If the task happens to run after cpu hot-plug offline, then it would not be running in a percpu_thread. Instead, it would be re-queued into a UNBOUND workqueue. This would trigger a warning if we enable kernel preemption. Signed-off-by: Andy Chiu --- kernel/trace/trace_hwlat.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c index b791524a6536..87258ddc2141 100644 --- a/kernel/trace/trace_hwlat.c +++ b/kernel/trace/trace_hwlat.c @@ -511,7 +511,16 @@ static int start_cpu_kthread(unsigned int cpu) static void hwlat_hotplug_workfn(struct work_struct *dummy) { struct trace_array *tr = hwlat_trace; - unsigned int cpu = smp_processor_id(); + unsigned int cpu; + + /* + * If the work is scheduled after CPU hotplug offline being invoked, + * then it would be queued into UNBOUNDED workqueue + */ + if (!is_percpu_thread()) + return; + + cpu = smp_processor_id(); mutex_lock(&trace_types_lock); mutex_lock(&hwlat_data.lock); -- 2.43.0