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[2a02:3100:b149:1401:90c6:65b4:35d:1e3d]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4b7e3279f9csm65132675e9.8.2026.11.07.05.17.32 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sat, 07 Nov 2026 05:17:33 -0800 (PST) From: Karl Mehltretter To: Andrew Morton Cc: Karl Mehltretter , Andrey Konovalov , Alexander Potapenko , Dmitry Vyukov , Marco Elver , Bradley Morgan , Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Sebastian Andrzej Siewior , Clark Williams , linux-rt-devel@lists.linux.dev, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org Subject: [PATCH v5 5/6] sched/core: Pause KCOV in try_to_wake_up() Date: Sat, 7 Nov 2026 14:17:09 +0100 Message-Id: <20261107131710.89264-6-kmehltretter@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <20261107131710.89264-1-kmehltretter@gmail.com> References: <20261107131710.89264-1-kmehltretter@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit try_to_wake_up() is built without KCOV instrumentation, but it calls helpers instrumented with KCOV, such as kthread_is_per_cpu(), CPU capacity helpers and SCHED_HRTICK arming. They can record into current while in_task() is true. During task-context wakeups such as a pipe write waking a reader, these helpers record coverage that depends on the target task and runqueue state into the waking task. Before commit feb5c9a2447a ("softirq: Preserve interrupt context on return from interrupt"), the IRQ-exit ktimersd wakeup under PREEMPT_RT also ran in task context and failed CONFIG_KCOV_SELFTEST in kthread_is_per_cpu(). Pause the wakeup body with kcov_pause_scope(). Take it before the preemption guard so preemption is re-enabled while KCOV remains paused. Wrapping only select_task_rq() would miss SCHED_HRTICK arming during enqueue. Signed-off-by: Karl Mehltretter --- kernel/sched/core.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 1691eb19f31a..4bd0d5736ccf 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4323,6 +4323,8 @@ bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success) */ int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) { + /* Callees instrumented with KCOV would leak coverage into current. */ + kcov_pause_scope(); guard(preempt)(); int cpu, success = 0; -- 2.39.5