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 8F3B524C074; Tue, 4 Mar 2025 19:20:36 +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=1741116036; cv=none; b=Tdz/qHsaSw/yhGCSogL29FMstkGto4Usd3Bih+UKZpOwMVsAZEORUEA42MNnG4+tDCoX15NQl5/TfNV+5L4aqPgZGc8w8EuTX7mvwEBsNXpHheX9lAGhXQGJFfradlaDP/1gigWloCK0kpxwK0q5Dl9wXJ1zoAUR2jpnH6NdV7w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741116036; c=relaxed/simple; bh=RG8802wCdCboJkQuLk9it4WgecYm0iYOq8Tyfe3o3EA=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=h3fFRDu7gLKUzHOuUFkP88mvcSAA/064TCTAUxq0fn0ecQPqZDRZjrpiX97RtLeeCupsoSz96h+R1+i6qe/kMUA6Ff9Tzdg5quYTQdC6czWL3b639AoxC9BcqHsFQbyxpTCpK9+i5mIujlU7g91NoKiSmphKN0zjFNUw4YNp8Tc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 05863C4CEE5; Tue, 4 Mar 2025 19:20:32 +0000 (UTC) Date: Tue, 4 Mar 2025 14:21:27 -0500 From: Steven Rostedt To: Boqun Feng Cc: rcu@vger.kernel.org, "Paul E. McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Uladzislau Rezki , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Davidlohr Bueso , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Valentin Schneider , Masami Hiramatsu , Shuah Khan , Sebastian Andrzej Siewior , Clark Williams , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-rt-devel@lists.linux.dev, Ankur Arora Subject: Re: [PATCH rcu 06/11] osnoise: provide quiescent states Message-ID: <20250304142127.391ca6bd@gandalf.local.home> In-Reply-To: <20250225035516.26443-7-boqun.feng@gmail.com> References: <20250225035516.26443-1-boqun.feng@gmail.com> <20250225035516.26443-7-boqun.feng@gmail.com> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 24 Feb 2025 19:55:11 -0800 Boqun Feng wrote: > From: Ankur Arora > > To reduce RCU noise for nohz_full configurations, osnoise depends > on cond_resched() providing quiescent states for PREEMPT_RCU=n > configurations. For PREEMPT_RCU=y configurations -- where > cond_resched() is a stub -- we do this by directly calling > rcu_momentary_eqs(). > > With (PREEMPT_LAZY=y, PREEMPT_DYNAMIC=n), however, we have a > configuration with (PREEMPTION=y, PREEMPT_RCU=n) where neither > of the above can help. > > Handle that by providing an explicit quiescent state here for all > configurations. > > As mentioned above this is not needed for non-stubbed cond_resched(), > but, providing a quiescent state here just pulls in one that a future > cond_resched() would provide, so doesn't cause any extra work for > this configuration. > > Cc: Paul E. McKenney > Cc: Daniel Bristot de Oliveira > Cc: Steven Rostedt Acked-by: Steven Rostedt (Google) -- Steve > Suggested-by: Paul E. McKenney > Acked-by: Daniel Bristot de Oliveira > Signed-off-by: Ankur Arora > Reviewed-by: Frederic Weisbecker > Signed-off-by: Paul E. McKenney > Signed-off-by: Boqun Feng > ---