From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 D5D472E7375; Fri, 31 Jul 2026 01:01:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785459718; cv=none; b=BZtbPxR+2syiCCvYY8m/EoTCOF9if/GDCjV9DzGAE8bPbqLWoLXMdyNDnegP8/erEkDgqeo5wT5MabJL5vV2xAYFCuhRToMGaouU3yO7dWnknwXkTPHY7yvGESOQSKYSCWQNdAPVhwz0iKa7ulta+ELADqSsSyqy1p88I3lt2xM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785459718; c=relaxed/simple; bh=w8G5cfYcQaM/fV8HeFYsbwcu7Zre3Ch3XgDCUA23tFQ=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=p7BuvfAKLFhAJS+EddPCGFbzary2F/Sh2VjBZpH51LKs3zu/bXRn/lWpZswrrfJ9/kYjfVLdh9sOra64F+SIbSTaVwAbre6g69OwTjTtm+up7RuOBLZKptyP5f8gjTKWuv6lNl6pg4irX74I3hxkW3tlM5g4wT70QgbrCJSW3aw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QhI6HjXd; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="QhI6HjXd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 402B71F00ADB; Fri, 31 Jul 2026 01:01:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785459715; bh=d90N1ezebPs22Y5VYk294ZLHVDI0r826ZopT19z5q6I=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=QhI6HjXdV+QvPqYaUthxq3peP2Nl3I5tsbrnPTDqguHYFfs6w293ZKHeqEAiZEjUk xOAmSi6RRtE1H1cBOdY0EzqM0tuVP7KfjahaOlXGhmtVdR0ReV7OPEHypx+3Sb/XKi kmRCL1a5WODL1vCL6JHh8ZYyUS0HQSyneg2Fm+a2WUZg97uDGDWCwM21RJCgBdJHSO fbI06HR2tzkRJS/7xAQVJA9nntfQ97h9A6ZyvUQHMKiLTk+b9nUsLXNJbkY6sigkJi +EI/aN2LxTeMPiUl6IjNDNp+XrzReJHpcldak0w9b7hVNlwjJrnHSmaXJdEQCIVFUn 0ZOba7mVrsABg== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id BEC1FCE17C1; Thu, 30 Jul 2026 18:01:54 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" Subject: [PATCH RFC 12/16] rcu: Mark interrupts-enabled accesses to rdp->cpu_no_qs.b.norm Date: Thu, 30 Jul 2026 18:01:49 -0700 Message-Id: <20260731010153.3531313-12-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <9de287bc-e565-4f21-bd3c-5c17792e6abc@paulmck-laptop> References: <9de287bc-e565-4f21-bd3c-5c17792e6abc@paulmck-laptop> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The rdp->cpu_no_qs.b.norm field is accessed only by the current CPU, but can be accessed both at task level and from interrupt handlers. All accesses from interrupts-enabled code must therefore be marked. This commit therefore converts from __this_cpu_read() to this_cpu_read(), from __this_cpu_write() to this_cpu_write(), and plain C-language accesses to READ_ONCE() and WRITE_ONCE(), but only in interrupts-enabled code. KCSAN located this issue. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 2 +- kernel/rcu/tree_plugin.h | 8 ++++---- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index c9780e7c0e2afa..377153e0d93440 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2540,7 +2540,7 @@ rcu_check_quiescent_state(struct rcu_data *rdp) * Was there a quiescent state since the beginning of the grace * period? If no, then exit and wait for the next call. */ - if (rdp->cpu_no_qs.b.norm) + if (READ_ONCE(rdp->cpu_no_qs.b.norm)) return; /* diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index c3db1ad4a2807a..353effac5a37f1 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -298,11 +298,11 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp) static void rcu_qs(void) { RCU_LOCKDEP_WARN(preemptible(), "rcu_qs() invoked with preemption enabled!!!\n"); - if (__this_cpu_read(rcu_data.cpu_no_qs.b.norm)) { + if (this_cpu_read(rcu_data.cpu_no_qs.b.norm)) { trace_rcu_grace_period(TPS("rcu_preempt"), __this_cpu_read(rcu_data.gp_seq), TPS("cpuqs")); - __this_cpu_write(rcu_data.cpu_no_qs.b.norm, false); + this_cpu_write(rcu_data.cpu_no_qs.b.norm, false); barrier(); /* Coordinate with rcu_flavor_sched_clock_irq(). */ WRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, false); } @@ -952,7 +952,7 @@ void rcu_read_unlock_strict(void) * __rcu_read_unlock(). */ rdp = this_cpu_ptr(&rcu_data); - rdp->cpu_no_qs.b.norm = false; + WRITE_ONCE(rdp->cpu_no_qs.b.norm, false); rcu_report_qs_rdp(rdp); udelay(rcu_unlock_delay); } @@ -980,7 +980,7 @@ static void rcu_qs(void) return; trace_rcu_grace_period(TPS("rcu_sched"), __this_cpu_read(rcu_data.gp_seq), TPS("cpuqs")); - __this_cpu_write(rcu_data.cpu_no_qs.b.norm, false); + this_cpu_write(rcu_data.cpu_no_qs.b.norm, false); if (this_cpu_read(rcu_data.cpu_no_qs.b.exp)) rcu_report_exp_rdp(this_cpu_ptr(&rcu_data)); } -- 2.40.1