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 6F8BC156C5B; Sun, 24 Mar 2024 23:11:37 +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=1711321898; cv=none; b=QioecpSqnINFHIAYhhxEeiRvtyip8oNSX6fCuiTO0swK1kynaBndmGNwfa6eJmxJdf9KyQzckfu1Oq2VSpAw6kQ16rePw1AyahDCDEaDfm8HTRLM5VPkljYGwGQ8620bhsjTUliA4tJB2fQJI1MuHhq4nLJLAcomVSNAfcjNscU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711321898; c=relaxed/simple; bh=Hu+ax5wSak1Lm1AsnCUL7UUmvAU1Wb0Gj04ZedWy7Do=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=CDF/StWbGRDViGBAzGO+pFi29xop3UkstltoCARFLBrRPEJ8NiN1RNDcOb7xpEKslCzv189NlViQtPibjllHqAnRa8TTyhqRmvcz5lXpXNZigmEu9fA0q6r4hE+InDMpqt5+hK74SLsopv+B65KlKs3+0TBJgIyhXH1aO/g1BTk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DNyuK8IZ; 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="DNyuK8IZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 81D6AC433C7; Sun, 24 Mar 2024 23:11:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711321897; bh=Hu+ax5wSak1Lm1AsnCUL7UUmvAU1Wb0Gj04ZedWy7Do=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DNyuK8IZSMS2YZEZAm+Hu6CrayuPcFIGoDSK11Yjihp4bRIaYfMn/Ey5dafXu2suj SlMj/MpsO2xNgqQi4mBhDnKmUs5q/2xrQFeg+N+4pUi+P1qYN7oRJfSILEecCXiAWs m5Wc69IYfmnc+6/8fYfqMSuGr45a3Rq2BdKYopG9wYFaud9R2pQo5lvISIW79p122d g4XrG8ifEtU8224NaBUv3dt2xPITnnmAxkD9zxMpN5I234hyvc0Ynpy26+GQYdjguR ed2w0DliwLrdV+IrB9ivbX8MA7/0UGadt4UWzpzTWEGW013DxXMsaiWjQ90+JhtDn6 JL/HpK/p3RD6g== 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 6.6 626/638] rcu: add a helper to report consolidated flavor QS Date: Sun, 24 Mar 2024 19:01:03 -0400 Message-ID: <20240324230116.1348576-627-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240324230116.1348576-1-sashal@kernel.org> References: <20240324230116.1348576-1-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: 8bit 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/90431d46ee112d2b0af04dbfe936faaca11810a5.1710877680.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 44aab5c0bd2c1..9ad656b28847f 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -252,6 +252,37 @@ do { \ cond_resched(); \ } while (0) +/** + * 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 will + * 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 would + * have more chance to invoke schedule() calls and provide necessary quiescent + * states. As a contrast, calling cond_resched() only won't achieve the same + * effect because cond_resched() does not provide RCU-Tasks quiescent states. + */ +#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) = jiffies; \ + } \ +} while (0) + /* * Infrastructure to implement the synchronize_() primitives in * TREE_RCU and rcu_barrier_() primitives in TINY_RCU. -- 2.43.0