From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 E58BE1B8853; Fri, 29 Mar 2024 12:44:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711716265; cv=none; b=GXKIjbmyP2K1oXKRJlHDDffcpniYKzEaZBvVKZu6SCyBqIxx6FXKgXjgY4M7HWE0l+ek6uP2Asd3yk5FCl64egCZaoGT1uTC7tSH2aTqW1f9UfP6kpE7Q6tWqjeU0vjLvSmeuua4DGzVZ14NLdzctcfiheSdSLwvTXaZBIWP6OQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711716265; c=relaxed/simple; bh=slTNCGICSXhv0R9PYIlhq5xx5106itMekrzuvhanb7M=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=RGL9TG7BiiySVwsTwpvufY4hbL38ZuopFSMY7/7mZmWxbQX5wS/p2htc86JKI5lPHXsPmol3XwT3JaBrTg9omCC7lXZlteG1pCOGUVo4ewIewk1VUTsg1s2lkM43xVL9l75Czz7NFKRvLjFdNjYK5ZljPxictkVfO/IKTZnl8hM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=c+Kz4QTs; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="c+Kz4QTs" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A1702C43330; Fri, 29 Mar 2024 12:44:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711716264; bh=slTNCGICSXhv0R9PYIlhq5xx5106itMekrzuvhanb7M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=c+Kz4QTsFlfd9P97Qxj7RXfWbLFiZNbfy3h2GajNbEuLYx5AOrqOoAF1RGtDXCEmx xOw4fb/tilNInjF619RdKEoxHjeYeu6VQ9uQun8YPPOIn7+3oNE7Q0Y1PFEkMchL5B iIgY73pQe87Y+BIEbC/TR2L93S/BwthjM28XOv5SniGHn1ST3hdUOjOai8z1CO8J7n TlwkM4dnDd/uyNLFK1gLk1uoNWU5qA51rGauEb9y5k0iCfgTK35kwWiLxpRY8O+K4L pGHYU1aRXG8o+T3B1f05G2EkzxiAc2rAITY1m93g8QssWfzmTkVP2qF4RStV6u9lYQ qFv/I4VksI+pA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Paul E. McKenney" , Steven Rostedt , Boqun Feng , Sasha Levin , frederic@kernel.org, quic_neeraju@quicinc.com, joel@joelfernandes.org, josh@joshtriplett.org, rcu@vger.kernel.org Subject: [PATCH AUTOSEL 6.6 29/75] rcu-tasks: Repair RCU Tasks Trace quiescence check Date: Fri, 29 Mar 2024 08:42:10 -0400 Message-ID: <20240329124330.3089520-29-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240329124330.3089520-1-sashal@kernel.org> References: <20240329124330.3089520-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.6.23 Content-Transfer-Encoding: 8bit From: "Paul E. McKenney" [ Upstream commit 2eb52fa8900e642b3b5054c4bf9776089d2a935f ] The context-switch-time check for RCU Tasks Trace quiescence expects current->trc_reader_special.b.need_qs to be zero, and if so, updates it to TRC_NEED_QS_CHECKED. This is backwards, because if this value is zero, there is no RCU Tasks Trace grace period in flight, an thus no need for a quiescent state. Instead, when a grace period starts, this field is set to TRC_NEED_QS. This commit therefore changes the check from zero to TRC_NEED_QS. Reported-by: Steven Rostedt Signed-off-by: Paul E. McKenney Tested-by: Steven Rostedt (Google) Signed-off-by: Boqun Feng Signed-off-by: Sasha Levin --- include/linux/rcupdate.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 44aab5c0bd2c1..f9173b972c7e2 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -189,9 +189,9 @@ void rcu_tasks_trace_qs_blkd(struct task_struct *t); do { \ int ___rttq_nesting = READ_ONCE((t)->trc_reader_nesting); \ \ - if (likely(!READ_ONCE((t)->trc_reader_special.b.need_qs)) && \ + if (unlikely(READ_ONCE((t)->trc_reader_special.b.need_qs) == TRC_NEED_QS) && \ likely(!___rttq_nesting)) { \ - rcu_trc_cmpxchg_need_qs((t), 0, TRC_NEED_QS_CHECKED); \ + rcu_trc_cmpxchg_need_qs((t), TRC_NEED_QS, TRC_NEED_QS_CHECKED); \ } else if (___rttq_nesting && ___rttq_nesting != INT_MIN && \ !READ_ONCE((t)->trc_reader_special.b.blocked)) { \ rcu_tasks_trace_qs_blkd(t); \ -- 2.43.0