From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f52.google.com (mail-wm1-f52.google.com [209.85.128.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 450633B42D3 for ; Tue, 11 Aug 2026 15:41:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.52 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786462893; cv=none; b=t3nbsEQHymOyqNt2ewuJTh1/FUIV0fnJVmlSKPYtuGNwYw2+/MWd5WKzvz477SKRkb5uf+zTgaKjhzJHvzZQEdiRB0oLzNlreVvnP2q7IL3/H1J1TUoDvH/vzNdX4+0ylAh9iWrnvJ6cMjjQV/Q73DnedV//6F1d1nLF8RnQnBE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786462893; c=relaxed/simple; bh=s2GsF/HuuhqRgEBoKnXETG0xb+lEGpCR6SzR1Bt2wXA=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Y3zMCnbMOw/zM90qYbhf6IfqJYvAEyNBuUdUeV9/ekS2yQoFSuCSkQjE5Vps+Kh1czoGoSJDN8iQulJsMHVFSzX1hbsLS+ZDqgJjTLnqFJLtkhQfZgXpFlaDfpTKSg6wbNY1pcGvV9+J4nPboB8HT7V5kmSycydEwMBtlwTlAwM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=Pwr5wpNy; arc=none smtp.client-ip=209.85.128.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Pwr5wpNy" Received: by mail-wm1-f52.google.com with SMTP id 5b1f17b1804b1-4954aff6088so28163315e9.3 for ; Tue, 11 Aug 2026 08:41:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1786462889; x=1787067689; darn=lists.linux.dev; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=RBg7Waiba/udBzajyRDSpAo3xkVEtASSwhEEWYlwPWA=; b=Pwr5wpNyo3HthUfAa60xn+rP7Xg3kNpOG2etgWTrVF7oMdk+DGUYTsV79078GzuZCd G6XorHnwfFyw+WqCIz/lVXEc6e2UjOw0XWIMYnMZopUm6jHK6aZtGWPY3WPfjqxZZWTF trs8Uq5ti1bxJjo/zKFtxlay+NiwdWMKa9oM3oLdTuFmO3h6hvUNUYvnpP78S9OeJ3ha i18IsKOYRT9AmAjn2iF57VSEDOhJv3etf67WButxvIwCyxmRquI23FduMcZLRDfL/ofM Qu/rwwlzIHI/fIKEo8c/0mkM39nXnyHDrKLGTy4ZovDMml6xHMiESGxkP3TUStJEwLLl K/ig== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786462889; x=1787067689; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=RBg7Waiba/udBzajyRDSpAo3xkVEtASSwhEEWYlwPWA=; b=Ce+w37jZaUhRCqqhty6miNorlWAofIbg8HM47hNYjGcUzpByEgSBuJ3j/WpIcDY9C1 zQc/3AVDygeHiXL8s29+pKsvhySksEuGLn+qHczNnPIME9b2ba1EidEm0Erx6VqWVOop ZXSju5us/6a0upl6WVSBrbr/rzvxcYTMzX7aq6ETx0lFmo1zywNgIN2oGhWHOcDb/ecF H3FLg7f/mnzkOb2vZLNjzCYqGTkbVZCvMJbo1PgN6wc6x9aJrOzqtBgd/huSCwAGe9p7 vJnaYxwlhyGopjdTIEdHK4L4FwW8Vm49CIU+SGtLdLyRnbCAX7KnEUBOyUP7NevOOPPT tlsA== X-Forwarded-Encrypted: i=1; AHgh+Rp46uzeUOF6ixfUtFZAT6OOL/DKIgqsWA5/khAR1cQLEq9HFW/2SW5tdHG7azD8ZBgKK5MRhJ2QxZtZl9kuAQ==@lists.linux.dev X-Gm-Message-State: AOJu0YzMuWrXg6n959nHv/IoHLX4lgDFuU7DY34uwTFcqM162jLMkgy6 i0SPpa7xJkex1P9JS2fmOLP0ywZ0LcgB8sQ3vW1rLLgvpAyCqCQ1WJ1S X-Gm-Gg: AR+sD11PIxFxqt9F8qDnWUefcEjmjR+H99PQoyjsDZsfibzaRoxhVGvnOHM2glHh17y TBH88y0DHXjrtucR2GNxwzKb4TjibmrdooYbpe7iIbs7Ezg6MAqYS+f5ZcLITR+iE4EfaI07uMG hoFgGbjFV1WtMPPZ+W0MqlQb+fj53na5gqGfdJmVfd2VME3U+POYhd//oiJSkeP1bUxfoLi+0np pDfAQn4KztdHWr1WCwXSX2IaCkn/OqwYndRmJiEWBm9MDZkwsRdher9xrM9JQzlFvJ5WO6DhfgJ i2C2huVqsNGzmY/Az0NhcOqp+zHkRyS06bjK8zIqdM26jMVUb8lkh3Y7wh7bZfYy53W/pQUoT4F KzKHeefJm1ITS6o9uwGil4tNaLLX/+knaMS5pK1O4UYUVGjBTTiwReFESwV5NNM3+xzzqX6rKog DGMHEb+Ry5VGrVAxAFZdlZ9S/ZLRqnGeZn6lp2NgQTmekf2AwtMmJTb/DXvjy8KIAIakHbiHViP WRfN5I7BPt9q5jdNyGrU54i06IHN0amhVjusurh0k8EtFbj9l60TmgLFOgahqy8F4YZiEBbFtqP 64ytTCOBnvr4mz29ACwLjcK1LDhJ7P/v7zz9A+G4AgzNef1WxaMjG+pLYagbOSIOiTeG X-Received: by 2002:a05:600c:821b:b0:493:e365:ace9 with SMTP id 5b1f17b1804b1-49978444628mr78764855e9.11.1786462889308; Tue, 11 Aug 2026 08:41:29 -0700 (PDT) Received: from localhost.localdomain (dynamic-2a02-3100-a133-e401-bc8e-d36c-2d08-c5e0.310.pool.telefonica.de. [2a02:3100:a133:e401:bc8e:d36c:2d08:c5e0]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4997aaa7aabsm1670275e9.7.2026.08.11.08.41.27 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Tue, 11 Aug 2026 08:41:28 -0700 (PDT) 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 v2 4/6] sched/core: Pause KCOV in __schedule() Date: Tue, 11 Aug 2026 17:41:09 +0200 Message-Id: <20260811154111.64669-5-kmehltretter@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <20260811154111.64669-1-kmehltretter@gmail.com> References: <20260811154111.64669-1-kmehltretter@gmail.com> Precedence: bulk X-Mailing-List: linux-rt-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit kernel/sched/ is not instrumented, but callees such as sched_clock(), architecture CPU-capacity helpers and profile_hits() are. During preemption and schedule() calls, instrumented callees can add nondeterministic scheduler coverage to current. With CONFIG_KCOV_SELFTEST added to x86_64 defconfig, the interrupt selftest fails under QEMU, detecting spurious coverage in arch_scale_cpu_capacity(). Annotating each callee would spread exclusions across architectures. Pause across __schedule() instead, extending the scheduler exclusion to its callees. KCOV_PAUSED remains set while a task is switched out. The guard in its resumed __schedule() frame restores the prior state. Fixes: 5c9a8750a640 ("kernel: add kcov code coverage") Assisted-by: Claude:claude-fable-5 Signed-off-by: Karl Mehltretter --- Notes: v2: - take guard(kcov_pause)() - clarify the test configuration and reword the pause comment kernel/sched/core.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 3cbf817f52a4a..e49f0bfa0ca73 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7073,6 +7073,9 @@ static void __sched notrace __schedule(int sched_mode) struct rq *rq; int cpu; + /* Instrumented callees would leak coverage into current. */ + guard(kcov_pause)(); + /* Trace preemptions consistently with task switches */ trace_sched_entry_tp(sched_mode == SM_PREEMPT); -- 2.53.0