From nobody Wed Oct 15 22:45:58 2025 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 C626C27F0A5; Sun, 24 Mar 2024 23:40:01 +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=1711323601; cv=none; b=ap3lkbHSNECGlMSkMNnwFBkGefKIvtKzkYa1AcjOWJKqnL81YStrwGTfVgRxR82kAK6bEKOXR25BRlhA4+vMvo6OcmRbu1uE6Zp/dTMsz8prHKAmyfkAIk0iKhgfZVZ8TBnDiwMCKRYRZZfCd3dF5YmYJlexKOk5HdhD8ucmMIA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711323601; c=relaxed/simple; bh=7YVNTYaVNaoUNrgLuMZUt7yXj8tc34KVJ9Dh9XYg5tY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sawHfg6VStDX0M+hPQ4dKVWtg2ffr1wMX2+KA46t45DkqixHoflVTDbOHAy/qIHBXuS35BGyiIlplvbaQrlXzb+BDImSlfYvqAVvCXxKnS4vvPYUeWsU4IcbVVXK01y7Fm5cgWInkIVUob9N2N+bzKKn0mz5z2ixh7Va80/yG0k= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ohj6r4/U; 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="Ohj6r4/U" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D3754C43399; Sun, 24 Mar 2024 23:40:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711323601; bh=7YVNTYaVNaoUNrgLuMZUt7yXj8tc34KVJ9Dh9XYg5tY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ohj6r4/UmOUmlBIiWPJqhFGIaW3jDFhJlycyIIrPdeTVyfDBmgrMUX1c111HYrss1 1A2u2pYfnBv7jUKR9ShzBLhTrmU/cDS5aNgynL2srgu6y/IB4lCGSvfGy4IZWnvbl5 Giaz4MSlV6aSWQm2sxTOp7lWoR/+wgKIDqHRdFtvgZDNrN3/XNTpDRNv1OxMKeCPe+ MQoEZUyb3aEuhXe/ZB27r6gGsQwxg2HUFRe6xqDcLG02g7K8DNz9RFzHZtT31zlhZD TGwBoirA50BE5tJb8UhKB9S6jxM41bWsiwUayh0eAFbigQ5Ju1Y+eSRaq904iH2eji HVOFlBDM5hllQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Yan Zhai , "Paul E . McKenney" , Jesper Dangaard Brouer , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.15 308/317] rcu: add a helper to report consolidated flavor QS Date: Sun, 24 Mar 2024 19:34:48 -0400 Message-ID: <20240324233458.1352854-309-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240324233458.1352854-1-sashal@kernel.org> References: <20240324233458.1352854-1-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 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Yan Zhai [ Upstream commit 1a77557d48cff187a169c2aec01c0dd78a5e7e50 ] When under heavy load, network processing can run CPU-bound for many tens of seconds. Even in preemptible kernels (non-RT kernel), this can block RCU Tasks grace periods, which can cause trace-event removal to take more than a minute, which is unacceptably long. This commit therefore creates a new helper function that passes through both RCU and RCU-Tasks quiescent states every 100 milliseconds. This hard-coded value suffices for current workloads. Suggested-by: Paul E. McKenney Reviewed-by: Jesper Dangaard Brouer Signed-off-by: Yan Zhai Reviewed-by: Paul E. McKenney Acked-by: Jesper Dangaard Brouer Link: https://lore.kernel.org/r/90431d46ee112d2b0af04dbfe936faaca11810a5.17= 10877680.git.yan@cloudflare.com Signed-off-by: Jakub Kicinski Stable-dep-of: d6dbbb11247c ("net: report RCU QS on threaded NAPI repolling= ") Signed-off-by: Sasha Levin --- include/linux/rcupdate.h | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index e3b12de36e924..d908af5917339 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -230,6 +230,37 @@ do { \ cond_resched(); \ } while (0) =20 +/** + * rcu_softirq_qs_periodic - Report RCU and RCU-Tasks quiescent states + * @old_ts: jiffies at start of processing. + * + * This helper is for long-running softirq handlers, such as NAPI threads = in + * networking. The caller should initialize the variable passed in as @old= _ts + * at the beginning of the softirq handler. When invoked frequently, this = macro + * will invoke rcu_softirq_qs() every 100 milliseconds thereafter, which w= ill + * provide both RCU and RCU-Tasks quiescent states. Note that this macro + * modifies its old_ts argument. + * + * Because regions of code that have disabled softirq act as RCU read-side + * critical sections, this macro should be invoked with softirq (and + * preemption) enabled. + * + * The macro is not needed when CONFIG_PREEMPT_RT is defined. RT kernels w= ould + * have more chance to invoke schedule() calls and provide necessary quies= cent + * states. As a contrast, calling cond_resched() only won't achieve the sa= me + * effect because cond_resched() does not provide RCU-Tasks quiescent stat= es. + */ +#define rcu_softirq_qs_periodic(old_ts) \ +do { \ + if (!IS_ENABLED(CONFIG_PREEMPT_RT) && \ + time_after(jiffies, (old_ts) + HZ / 10)) { \ + preempt_disable(); \ + rcu_softirq_qs(); \ + preempt_enable(); \ + (old_ts) =3D jiffies; \ + } \ +} while (0) + /* * Infrastructure to implement the synchronize_() primitives in * TREE_RCU and rcu_barrier_() primitives in TINY_RCU. --=20 2.43.0