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 B050355E74; Sun, 24 Mar 2024 17:07:13 +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=1711300033; cv=none; b=d5lptE+TRVbLHQQv2v8FYn4pXLY9+Ky6jHOAlEu1eIEMzsPcpgbV/J+3Ir6Y4syErm5ul9UxLL3MQjpIdBFwusL9CDlhqGkJ0BvbYMSe942WwErXQPC1JqKhSYjW9oV8pBTJNgZIOFApGRAQGQKGnF/zOUiTJFStTP9jcVBnf6w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711300033; c=relaxed/simple; bh=WPIjX/2qHFPCedFEYL9s01CISXiCP6wWXcAuXar04gU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fEAt7uKhIh+7fV4PJkkrMVhbDDY3JsHUpcGwP7qVsXWtD+lCR4uMN2K6Br+NWe4hoX86RbEpuHInrLooe5Fu5oWzeZSqgyHxCjhkg15OEC3EI0I8yNCuSKcElB7/jMGNKzzB7qMvtzlqBoi4vBtIiTfKg9tGApZBiiMo16BZIaI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DcSR9zVP; 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="DcSR9zVP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1D76FC43394; Sun, 24 Mar 2024 17:07:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711300033; bh=WPIjX/2qHFPCedFEYL9s01CISXiCP6wWXcAuXar04gU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DcSR9zVPe8VR9tyvUyoqcUmnRujBIpegzsqs/SzSGSeDKoSRmAXt64MLcV7XmGNcj BkiLA0ODUf/Gi3jIQ3SOwOPaeCoMKGVDOelEEeU6631f/z46FSxFr9K1vRE2XKrzZA pgN3C9s4CGZElU6QM6kPV6k9GWDDfTK5yk4snXMKLMTELb+cIJUDqebK7T1O6bhRKx Upi3o1KvyR+k0CjU/UA0fKP8570WYs1ufTC10BHN11S0ZK6AcDALME9wrXYaG7zdxY +O/o3anEqFK/s1Is+TuXv47HWgJ6aH/ropAsdEo5YXUfKSSsu2RQg3Nw/BZ6E1ajMp 0xT0JCx74LQRg== 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 6.1 2/7] rcu-tasks: Repair RCU Tasks Trace quiescence check Date: Sun, 24 Mar 2024 13:07:02 -0400 Message-ID: <20240324170709.546465-2-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240324170709.546465-1-sashal@kernel.org> References: <20240324170709.546465-1-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 6.1.82 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 d2507168b9c7b..e7474d7833424 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -205,9 +205,9 @@ 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