From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754379AbeDWIvw (ORCPT ); Mon, 23 Apr 2018 04:51:52 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:60160 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754029AbeDWIvq (ORCPT ); Mon, 23 Apr 2018 04:51:46 -0400 Date: Mon, 23 Apr 2018 10:51:27 +0200 From: Peter Zijlstra 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, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel.opensrc@gmail.com Subject: Re: [PATCH tip/core/rcu 01/22] sched: Make non-production PREEMPT cond_resched() help Tasks RCU Message-ID: <20180423085127.GR4064@hirez.programming.kicks-ass.net> References: <20180423023150.GA21533@linux.vnet.ibm.com> <1524450747-22778-1-git-send-email-paulmck@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1524450747-22778-1-git-send-email-paulmck@linux.vnet.ibm.com> User-Agent: Mutt/1.9.3 (2018-01-21) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Apr 22, 2018 at 07:32:06PM -0700, Paul E. McKenney wrote: > In CONFIG_PREEMPT=y kernels, cond_resched() is a complete no-op, and > thus cannot help advance Tasks-RCU grace periods. However, such grace > periods are only an issue in non-production benchmarking runs of the > Linux kernel. This commit therefore makes cond_resched() invoke > rcu_note_voluntary_context_switch() for kernels implementing Tasks RCU > even in CONFIG_PREEMPT=y kernels. I'm confused.. why is having this conditional on TRACEPOINT_BENCHMARK a sane idea? > > Reported-by: Steven Rostedt > Signed-off-by: Paul E. McKenney > --- > include/linux/sched.h | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index b3d697f3b573..fe8f7178a22d 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -1617,6 +1617,12 @@ static inline int test_tsk_need_resched(struct task_struct *tsk) > */ > #ifndef CONFIG_PREEMPT > extern int _cond_resched(void); > +#elif defined(CONFIG_TRACEPOINT_BENCHMARK) > +static inline int _cond_resched(void) > +{ > + rcu_note_voluntary_context_switch(current); > + return 0; > +} > #else > static inline int _cond_resched(void) { return 0; } > #endif > -- > 2.5.2 >