From mboxrd@z Thu Jan 1 00:00:00 1970 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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 509F8C4740A for ; Sat, 5 Oct 2019 16:42:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2557E22477 for ; Sat, 5 Oct 2019 16:42:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570293737; bh=0IjufT6jSKEMpep9FAXN5Dd37rK1JuJ8DqvWyKI29Bg=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=gG3OyJgABR7Vtcx4LtSWE8PPlRnVdK2HTf2ZlHjlsC13EvmvdwhOIEDsQ5glHrYGB qnUT6swcQ6o8sL8dRdRXpyeI5OsO8L+cxXhFX5NsLUU5BAOE5ix70pmNNJPkMguKW0 HmRpO3AH6f0gM8rdKzqdtcfq6NdLLWsumNyn99G8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729083AbfJEQmQ (ORCPT ); Sat, 5 Oct 2019 12:42:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:45534 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726285AbfJEQmQ (ORCPT ); Sat, 5 Oct 2019 12:42:16 -0400 Received: from paulmck-ThinkPad-P72 (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 95ACD22475; Sat, 5 Oct 2019 16:42:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570293735; bh=0IjufT6jSKEMpep9FAXN5Dd37rK1JuJ8DqvWyKI29Bg=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=r1VIV/pSNbhV7SmQkcEOvBjs6+w/6WdcDyB38D3oR2YDgZcuCHgCryf9I0wK0AxJ+ jjUXJwYQT09klEQr++n/vjR0tNTlWUwKJlfUGKH5UMUxKCYXVWP7pujU6nGY6PvgTh I3D6ZLlQ8aQYO9J1z0HgEVfY35wmM5q+E3nul53s= Date: Sat, 5 Oct 2019 09:42:14 -0700 From: "Paul E. McKenney" To: Frederic Weisbecker Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org Subject: Re: [PATCH tip/core/rcu 03/12] rcu: Force on tick when invoking lots of callbacks Message-ID: <20191005164214.GI2689@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20191003013834.GA12927@paulmck-ThinkPad-P72> <20191003013903.13079-3-paulmck@kernel.org> <20191003140955.GA27003@lenoir> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191003140955.GA27003@lenoir> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Thu, Oct 03, 2019 at 04:10:52PM +0200, Frederic Weisbecker wrote: > On Wed, Oct 02, 2019 at 06:38:54PM -0700, paulmck@kernel.org wrote: > > From: "Paul E. McKenney" > > > > Callback invocation can run for a significant time period, and within > > CONFIG_NO_HZ_FULL=y kernels, this period will be devoid of scheduler-clock > > interrupts. In-kernel execution without such interrupts can cause all > > manner of malfunction, with RCU CPU stall warnings being but one result. > > > > This commit therefore forces scheduling-clock interrupts on whenever more > > than a few RCU callbacks are invoked. Because offloaded callback invocation > > can be preempted, this forcing is withdrawn on each context switch. This > > in turn requires that the loop invoking RCU callbacks reiterate the forcing > > periodically. > > > > [ paulmck: Apply Joel Fernandes TICK_DEP_MASK_RCU->TICK_DEP_BIT_RCU fix. ] > > Signed-off-by: Paul E. McKenney > > --- > > kernel/rcu/tree.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > index 8110514..db673ae 100644 > > --- a/kernel/rcu/tree.c > > +++ b/kernel/rcu/tree.c > > @@ -2151,6 +2151,8 @@ static void rcu_do_batch(struct rcu_data *rdp) > > rcu_nocb_unlock_irqrestore(rdp, flags); > > > > /* Invoke callbacks. */ > > + if (IS_ENABLED(CONFIG_NO_HZ_FULL)) > > No need for the IS_ENABLED(), the API takes care of that. > > > + tick_dep_set_task(current, TICK_DEP_BIT_RCU); > > rhp = rcu_cblist_dequeue(&rcl); > > for (; rhp; rhp = rcu_cblist_dequeue(&rcl)) { > > debug_rcu_head_unqueue(rhp); > > @@ -2217,6 +2219,8 @@ static void rcu_do_batch(struct rcu_data *rdp) > > /* Re-invoke RCU core processing if there are callbacks remaining. */ > > if (!offloaded && rcu_segcblist_ready_cbs(&rdp->cblist)) > > invoke_rcu_core(); > > + if (IS_ENABLED(CONFIG_NO_HZ_FULL)) > > Same here. Good catches! Applied, thank you! Thanx, Paul > Thanks. > > > + tick_dep_clear_task(current, TICK_DEP_BIT_RCU); > > } > > > > /* > > -- > > 2.9.5 > >