From patchwork Thu Aug 5 08:01:23 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Juri Lelli X-Patchwork-Id: 492537 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8B43CC4338F for ; Thu, 5 Aug 2021 08:01:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6ED0A61040 for ; Thu, 5 Aug 2021 08:01:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239188AbhHEIB7 (ORCPT ); Thu, 5 Aug 2021 04:01:59 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:49240 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231377AbhHEIB6 (ORCPT ); Thu, 5 Aug 2021 04:01:58 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1628150504; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=K2ghss8N4x5+qkA+P5j44zXDC0+0LL6Ii3eIbL81nCo=; b=RhYuf7WGRwH2LeAcDTkSwR6MRMb3FeFRGs5M7lD/VqWFjl987/i9qkfwuMOlYrkuq/TDNg ezG+t9sdXAlpcQBPir6nSCU9lhUeFpHs27TX3kSQ4jzwPy4+enKqGrQpUqcsP/ICXmMu9+ ZRT7dC6oz2JOX0rVUmqQPbJlnGD12/Q= Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-578-ac4WVnHvODKb_sl0eQZIpA-1; Thu, 05 Aug 2021 04:01:43 -0400 X-MC-Unique: ac4WVnHvODKb_sl0eQZIpA-1 Received: by mail-ed1-f72.google.com with SMTP id u4-20020a50eac40000b02903bddc52675eso2584570edp.4 for ; Thu, 05 Aug 2021 01:01:43 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=K2ghss8N4x5+qkA+P5j44zXDC0+0LL6Ii3eIbL81nCo=; b=Q7zwPHSRwWJ1WXwSIzLEYXFazOrrhAXzDje3yzoUXKYVyC0PmbQDsmQj8Sn8kB5vnh wcmSA7EX1KOqg02y9bNM/kCWv4JNhssPGQxIjHdvUUxXE7vOCJyxfZUW62MCJgBujN95 yo3f9QQKDEpkhzpc59VHwN6mfsyuS296+qwi4hGzSBZaqZzdbG6NDWrHjgkXm0mkeSZu Fr1FTbupenfvka4babyKhDzYwHJviC9oHMjMBNOBvRN28qyuqsX1SdgD6yEPh/k38zEx I5n92JUuiZAxP4dG9dqnaHOruySkLoaC2p6TQqMwBhXnL8b4fvEqIfOYOSxPNDnCZGjE qrxA== X-Gm-Message-State: AOAM532GC+uIdDPYeP+4tWFjVH5u1RsG7pBPcBPE6yBpwf02QT0HqwOK NzM0q5TQi7TVsakB/5w6y9B20ejEt21l0qvir3kotV4VnM2wcxl2Yas4rGrY2QldcBA54AhI5QT oxN6oBbiVZ7+BA2RTf5AUoTrJRYU= X-Received: by 2002:a17:906:8443:: with SMTP id e3mr3653487ejy.46.1628150502340; Thu, 05 Aug 2021 01:01:42 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxRZM+Kqhl+Aet0UV2RVMRB/Uaogk6zdAX2mcOhTRyejWYvAHB4AjPVaC92ipDE99MWEylOig== X-Received: by 2002:a17:906:8443:: with SMTP id e3mr3653470ejy.46.1628150502187; Thu, 05 Aug 2021 01:01:42 -0700 (PDT) Received: from localhost.localdomain.com ([151.29.52.108]) by smtp.gmail.com with ESMTPSA id n15sm1925851edw.70.2021.08.05.01.01.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Aug 2021 01:01:41 -0700 (PDT) From: Juri Lelli To: paulmck@kernel.org, josh@joshtriplett.org Cc: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, peterz@infradead.org, bigeasy@linutronix.de, tglx@linutronix.de, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, joel@joelfernandes.org, rcu@vger.kernel.org, Juri Lelli Subject: [PATCH] rcu: Make rcu_normal_after_boot writable on RT Date: Thu, 5 Aug 2021 10:01:23 +0200 Message-Id: <20210805080123.16320-1-juri.lelli@redhat.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org Certain configurations (e.g., systems that make heavy use of netns) need to use synchronize_rcu_expedited() to service RCU grace periods even after boot. Even though synchronize_rcu_expedited() has been traditionally considered harmful for RT for the heavy use of IPIs, it is perfectly usable under certain conditions (e.g. nohz_full). Make rcupdate.rcu_normal_after_boot= again writeable on RT, but keep its default value to 1 (enabled) to avoid regressions. Users who need synchronize_rcu_expedited() will boot with rcupdate.rcu_normal_after_ boot=0 in the kernel cmdline. Signed-off-by: Juri Lelli --- kernel/rcu/update.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index c21b38cc25e9..0fdbf937edac 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -57,9 +57,7 @@ module_param(rcu_expedited, int, 0); module_param(rcu_normal, int, 0); static int rcu_normal_after_boot = IS_ENABLED(CONFIG_PREEMPT_RT); -#ifndef CONFIG_PREEMPT_RT module_param(rcu_normal_after_boot, int, 0); -#endif #endif /* #ifndef CONFIG_TINY_RCU */ #ifdef CONFIG_DEBUG_LOCK_ALLOC