From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752081AbeBZE5x (ORCPT ); Sun, 25 Feb 2018 23:57:53 -0500 Received: from mail.kernel.org ([198.145.29.99]:58744 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751947AbeBZE5w (ORCPT ); Sun, 25 Feb 2018 23:57:52 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0EE4D20693 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Sun, 25 Feb 2018 23:57:48 -0500 From: Steven Rostedt To: "Paul E. McKenney" Cc: 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, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, Ingo Molnar Subject: Re: [PATCH tip/core/rcu 06/10] trace: Eliminate cond_resched_rcu_qs() in favor of cond_resched() Message-ID: <20180225235748.4ce882e5@vmware.local.home> In-Reply-To: <20180225181730.GA3963@linux.vnet.ibm.com> References: <20171201192122.GA19301@linux.vnet.ibm.com> <1512156104-20104-6-git-send-email-paulmck@linux.vnet.ibm.com> <20180224151240.0d63a059@vmware.local.home> <20180225174927.GC2855@linux.vnet.ibm.com> <20180225181730.GA3963@linux.vnet.ibm.com> X-Mailer: Claws Mail 3.15.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 25 Feb 2018 10:17:30 -0800 "Paul E. McKenney" wrote: > And probably not. You are probably running CONFIG_PREEMPT=y (otherwise > RCU-tasks is trivial), so cond_resched() is a complete no-op: > > static inline int _cond_resched(void) { return 0; } > > I could make this call rcu_all_qs(), but I would not expect Peter Zijlstra > to be at all happy with that sort of change. > > And the people who asked for the cond_resched() work probably aren't > going to be happy with the resumed proliferation of cond_resched_rcu_qs(). > > Hmmm... Grasping at straws... Could we make cond_resched() be something > like a tracepoint and instrument them with cond_resched_rcu_qs() if the > current RCU-tasks grace period ran for more that (say) a minute of its > ten-minute stall-warning span? > Instead of monkeying with cond_resched(), since this is "special" code, why don't I just have that code call it directly? cond_resched(); rcu_note_voluntary_context_switch(current); -- Steve