From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1B39237B019; Mon, 11 May 2026 12:07:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778501241; cv=none; b=beKrbu4ctS4aKOaO76kWHaI6JYjC/+i7lrxABN5ji3BSXPv/L8WA2n7WEYWJ2KS/N1UmX6U8x9XPXSZQefhuS9J5PIDaNBf6ViBdaqQCkmIDA2HIJeDA/qsslenSS/jui/NB1VRLzdm6K+1tjC2Lp59kj5jNCTjgXqLocdPXuDs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778501241; c=relaxed/simple; bh=74XIwVKXNdZdW2lgIMAjqDEX5lPpAsOLQAevkzqcgxU=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=jlFDwjYljH7JNheFWKYtrvhdJ+9LhDcmR1ZHP4TCrK6qs2zVur6F6m7KJsbh4G+o2roPu4ebCn+7nXeQqd4MNJHpOnfDR5dP7ioi+V9B0Gv1Mcouov2GUcvgMQJ4uTKDrdNodHSG1Wc7NiQfhRov1HhxMqjZb+cAruaSRKpt+C0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=ewnTeeEs; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="ewnTeeEs" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-ID:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=/nBno72/K1OUhxB+muvWZ/oNtRySVk9xDO45q62blsY=; b=ewnTeeEsMU8nUt37TAm0yjckfz GYMDoTRT5Vqxq8/OjWMvWgIQ9a899LBv4ZoyQVvpI6yxLLT4iO1Njb0svRpYA2IOjYpmC39UTsWhv H58x6UfG4D0DXNWtQtT+ORERZ9dZ3JvazORCHE1iL/NHBbY9VP5aNesTCLzqsRYOV8JPp+C2rQqXs A1ktYUeJ6p3HHsATxB6XSin6umm8DIvCA8y7vim5ElIwZ00UwoTUoLv0hcyOlbSgN66nJF0/mPwRO NpDq54iAshYiaIABii/smhW6TDzTqk1w71MJSWEwKh7VarRL4U5sDlw++uJcxzZc6HInUDAqA9gXe l/sb41JQ==; Received: from 2001-1c00-8d85-4b00-266e-96ff-fe07-7dcc.cable.dynamic.v6.ziggo.nl ([2001:1c00:8d85:4b00:266e:96ff:fe07:7dcc] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1wMPPZ-0000000BZMS-1x3u; Mon, 11 May 2026 12:07:03 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 0) id 115B8301261; Mon, 11 May 2026 14:07:00 +0200 (CEST) Message-ID: <20260511120627.176946327@infradead.org> User-Agent: quilt/0.68 Date: Mon, 11 May 2026 13:31:06 +0200 From: Peter Zijlstra To: mingo@kernel.org Cc: longman@redhat.com, chenridong@huaweicloud.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, jstultz@google.com, kprateek.nayak@amd.com, qyousef@layalina.io Subject: [PATCH v2 02/10] sched: Use {READ,WRITE}_ONCE() for preempt_dynamic_mode References: <20260511113104.563854162@infradead.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 Robots figured out you can read and write this concurrently and got 'upset'. Gemini even noted sched_dynamic_show() can generate 'confusing' output if it observed different values during the printing. Signed-off-by: Peter Zijlstra (Intel) --- kernel/sched/core.c | 15 ++++++++------- kernel/sched/debug.c | 5 +++-- 2 files changed, 11 insertions(+), 9 deletions(-) --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7743,7 +7743,7 @@ static void __sched_dynamic_update(int m break; } - preempt_dynamic_mode = mode; + WRITE_ONCE(preempt_dynamic_mode, mode); } void sched_dynamic_update(int mode) @@ -7784,12 +7784,13 @@ static void __init preempt_dynamic_init( } } -# define PREEMPT_MODEL_ACCESSOR(mode) \ - bool preempt_model_##mode(void) \ - { \ - WARN_ON_ONCE(preempt_dynamic_mode == preempt_dynamic_undefined); \ - return preempt_dynamic_mode == preempt_dynamic_##mode; \ - } \ +# define PREEMPT_MODEL_ACCESSOR(mode) \ + bool preempt_model_##mode(void) \ + { \ + int mode = READ_ONCE(preempt_dynamic_mode); \ + WARN_ON_ONCE(mode == preempt_dynamic_undefined); \ + return mode == preempt_dynamic_##mode; \ + } \ EXPORT_SYMBOL_GPL(preempt_model_##mode) PREEMPT_MODEL_ACCESSOR(none); --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -239,6 +239,7 @@ static ssize_t sched_dynamic_write(struc static int sched_dynamic_show(struct seq_file *m, void *v) { int i = (IS_ENABLED(CONFIG_PREEMPT_RT) || IS_ENABLED(CONFIG_ARCH_HAS_PREEMPT_LAZY)) * 2; + int mode = READ_ONCE(preempt_dynamic_mode); int j; /* Count entries in NULL terminated preempt_modes */ @@ -247,10 +248,10 @@ static int sched_dynamic_show(struct seq j -= !IS_ENABLED(CONFIG_ARCH_HAS_PREEMPT_LAZY); for (; i < j; i++) { - if (preempt_dynamic_mode == i) + if (mode == i) seq_puts(m, "("); seq_puts(m, preempt_modes[i]); - if (preempt_dynamic_mode == i) + if (mode == i) seq_puts(m, ")"); seq_puts(m, " ");