From patchwork Wed Jun 21 02:32:35 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexei Starovoitov X-Patchwork-Id: 13286588 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A52EDEB64D8 for ; Wed, 21 Jun 2023 02:33:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229885AbjFUCdV (ORCPT ); Tue, 20 Jun 2023 22:33:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46850 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229658AbjFUCdT (ORCPT ); Tue, 20 Jun 2023 22:33:19 -0400 Received: from mail-pf1-x431.google.com (mail-pf1-x431.google.com [IPv6:2607:f8b0:4864:20::431]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 067D1B7; Tue, 20 Jun 2023 19:33:19 -0700 (PDT) Received: by mail-pf1-x431.google.com with SMTP id d2e1a72fcca58-668704a5b5bso3119179b3a.0; Tue, 20 Jun 2023 19:33:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1687314798; x=1689906798; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=QJFALLSA0Zej+KutPxvztQdPk2ASSkOODjkIKNtNWzE=; b=qKNLJ1TSm1wXJWHwDkxH9F/UzLEIyQuftptzJGSxXDZzZPkvJMyfYJNfy2DOcRGeby Ahrs4o4hF7ae485L/o3G/NhiZHxL9sbkDJbII4IwY0v1V4LrOL734V5wObhehFb8ttpS XaHaIIpwRAhslQf3NXcsyysXV3VY5ftaURSaA5PhveF7rhdlCTvqISXfDgIub596Yn2i Pc/nNDoeIPjzvtdYOktGRck8y7vQUuw8nz3CYRFAWalA6YOxbhg7MzLviKaF+eLwP9K6 0bbbmDnyeVP+RNEkaDsB05pQoH2sarACh0VNBmDab31tir1hSfa8hRXpeEIzS7FI2rn1 vRjg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1687314798; x=1689906798; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=QJFALLSA0Zej+KutPxvztQdPk2ASSkOODjkIKNtNWzE=; b=J1VSCLpj6u87pbZl9OUII/NLE1ChQalcu8SnheiA0Db+VBogd6wd67iAnLaSeRgT/s hWCYrXkAGNsMV3maUU32tmsATJciaUJwXCb9BGmLh/Syn9uxMxt8Wi/PZRojMh0hFG0h KOBt54tjOrzymgN0U3UAWsqdHuKRxTYLgo8GTHM0IkQZvNXo5uqghoyp4hpfVJPHLYy6 f6FaqmNKIwf5xKaYYjfB3q9SUT8ut8lBldlGiFK0yVJcN5fAq+tC8ei5qTIU9pFY7bmU KjmkPup42MYAgRmYNTN3Nz/R8rGCJMgq5/hjZvHTHNgFjJqk2gGaNUrsXxnnmMtLNQVn b3fQ== X-Gm-Message-State: AC+VfDy0woEFBt2OiUW90e/e+8F790b4AHWFFpUoUnS9nA9PhHOYwgIj zgwafroPG52vkJxMRDzeYwQ= X-Google-Smtp-Source: ACHHUZ76+u1Qgg4DLJ6cVJswS48hyHGNQJ1ZvA7sgFImciRpXkia92T++/EuLi7ytgn24KKIS3/i7Q== X-Received: by 2002:a05:6a00:1a56:b0:658:c1a9:becc with SMTP id h22-20020a056a001a5600b00658c1a9beccmr20215081pfv.12.1687314798237; Tue, 20 Jun 2023 19:33:18 -0700 (PDT) Received: from localhost.localdomain ([2620:10d:c090:400::5:e719]) by smtp.gmail.com with ESMTPSA id d20-20020aa78154000000b00666a83bd544sm1894485pfn.23.2023.06.20.19.33.16 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Tue, 20 Jun 2023 19:33:17 -0700 (PDT) From: Alexei Starovoitov To: daniel@iogearbox.net, andrii@kernel.org, void@manifault.com, houtao@huaweicloud.com, paulmck@kernel.org Cc: tj@kernel.org, rcu@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, kernel-team@fb.com Subject: [PATCH bpf-next 09/12] rcu: Export rcu_request_urgent_qs_task() Date: Tue, 20 Jun 2023 19:32:35 -0700 Message-Id: <20230621023238.87079-10-alexei.starovoitov@gmail.com> X-Mailer: git-send-email 2.39.2 (Apple Git-143) In-Reply-To: <20230621023238.87079-1-alexei.starovoitov@gmail.com> References: <20230621023238.87079-1-alexei.starovoitov@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: "Paul E. McKenney" If a CPU is executing a long series of non-sleeping system calls, RCU grace periods can be delayed for on the order of a couple hundred milliseconds. This is normally not a problem, but if each system call does a call_rcu(), those callbacks can stack up. RCU will eventually notice this callback storm, but use of rcu_request_urgent_qs_task() allows the code invoking call_rcu() to give RCU a heads up. This function is not for general use, not yet, anyway. Reported-by: Alexei Starovoitov Signed-off-by: Paul E. McKenney Signed-off-by: Alexei Starovoitov --- include/linux/rcutiny.h | 2 ++ include/linux/rcutree.h | 1 + kernel/rcu/rcu.h | 2 -- 3 files changed, 3 insertions(+), 2 deletions(-) diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index 7f17acf29dda..7b949292908a 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -138,6 +138,8 @@ static inline int rcu_needs_cpu(void) return 0; } +static inline void rcu_request_urgent_qs_task(struct task_struct *t) { } + /* * Take advantage of the fact that there is only one CPU, which * allows us to ignore virtualization-based context switches. diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 56bccb5a8fde..126f6b418f6a 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -21,6 +21,7 @@ void rcu_softirq_qs(void); void rcu_note_context_switch(bool preempt); int rcu_needs_cpu(void); void rcu_cpu_stall_reset(void); +void rcu_request_urgent_qs_task(struct task_struct *t); /* * Note a virtualization-based context switch. This is simply a diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index 4a1b9622598b..6f5fb3f7ebf3 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -493,7 +493,6 @@ static inline void rcu_expedite_gp(void) { } static inline void rcu_unexpedite_gp(void) { } static inline void rcu_async_hurry(void) { } static inline void rcu_async_relax(void) { } -static inline void rcu_request_urgent_qs_task(struct task_struct *t) { } #else /* #ifdef CONFIG_TINY_RCU */ bool rcu_gp_is_normal(void); /* Internal RCU use. */ bool rcu_gp_is_expedited(void); /* Internal RCU use. */ @@ -508,7 +507,6 @@ void show_rcu_tasks_gp_kthreads(void); #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */ static inline void show_rcu_tasks_gp_kthreads(void) {} #endif /* #else #ifdef CONFIG_TASKS_RCU_GENERIC */ -void rcu_request_urgent_qs_task(struct task_struct *t); #endif /* #else #ifdef CONFIG_TINY_RCU */ #define RCU_SCHEDULER_INACTIVE 0