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 555BA1B94B; Sun, 24 Mar 2024 17:06:49 +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=1711300009; cv=none; b=GSfEsGx8ojzbI1UIRhJc8jS0VjzdJIiWQCn9g36u8jGuq+4a2PZuK0DqFuPl85PIxDjMOwJu2epPIqexvoy+8SeaefMglxv+Vgd398ArMahMSTdcCO9Jcznhv68JCCzUURCvZnhEKZsxFEcqT76tYtJetF+RLo+g6/tOb2W/OA8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711300009; c=relaxed/simple; bh=slTNCGICSXhv0R9PYIlhq5xx5106itMekrzuvhanb7M=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=UssRqOYFCvaD7QYyPpkt32latGHHu+TrFrtZRl+btzb1Bn17tGLzYFDOJQEwa7Shl85GA02n+vby3lri1MCmKaOHqC+e7sKWNGvlP66GnZz9haHNU5Or5BchEdrnu6qceQh1KEcxCNo/4UHbyFFQW0IeXp2+Y7a4pO4myJvzWfA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lAvvk6Bd; 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="lAvvk6Bd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0DFB5C433B1; Sun, 24 Mar 2024 17:06:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711300009; bh=slTNCGICSXhv0R9PYIlhq5xx5106itMekrzuvhanb7M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lAvvk6BdouyZ5ad9CrQa2cYMzsbRCZTMWGyKwz6X1pV+N1tBTauCG1Xq+nbPCqRp/ SbsDnsF65I+8t8cXGBkcSKo7In3UQPR4J0MCFjaP9CoHa/SAtrRzL1FKDHsfmON5+6 kqKmdvxsaUmCMzVtjnluHOsjcFMUwvDWtqZa1j6BVsZPvYbarfhQ2rrlh78JFVoN0Q rUqvck1g4vRicbSaaWqDDX2CXUueQp7oKkRbiT50cM9qO9obACK1LXfiQFEyq109Rd R6JMEX2zKglqaZM9vnuzkOc4thsr4y702FjD+KqmxL9uai2dfJEcZvrr/L86i2ip2M sDxmo7FhWNUdA== 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 02/11] rcu-tasks: Repair RCU Tasks Trace quiescence check Date: Sun, 24 Mar 2024 13:06:32 -0400 Message-ID: <20240324170645.546220-2-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240324170645.546220-1-sashal@kernel.org> References: <20240324170645.546220-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.6.22 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