From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935629AbeB1XM5 (ORCPT ); Wed, 28 Feb 2018 18:12:57 -0500 Received: from mail.kernel.org ([198.145.29.99]:59154 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935525AbeB1XM4 (ORCPT ); Wed, 28 Feb 2018 18:12:56 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4D847214EE 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: Wed, 28 Feb 2018 18:12:52 -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: <20180228181252.55e0590c@vmware.local.home> In-Reply-To: <20180227153646.GD3777@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> <20180225183944.GA8840@linux.vnet.ibm.com> <20180226212920.43e25d6e@vmware.local.home> <20180227153646.GD3777@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 Tue, 27 Feb 2018 07:36:46 -0800 "Paul E. McKenney" wrote: > > > --- a/include/linux/sched.h > > > +++ b/include/linux/sched.h > > > @@ -1589,6 +1589,12 @@ static inline int test_tsk_need_resched(struct task_struct *tsk) > > > */ > > > #ifndef CONFIG_PREEMPT > > > extern int _cond_resched(void); > > > +#elif defined(CONFIG_TASKS_RCU) > > > +static inline int _cond_resched(void) > > > +{ > > > + rcu_note_voluntary_context_switch(current); > > > + return 0; > > > +} > > > #else > > > static inline int _cond_resched(void) { return 0; } > > > #endif > > > > > > This does work, but so does the below, without causing cond_resched() > > from being something other than a nop of CONFIG_PREEMPT. > > True, but based on the cond_resched_rcu_qs() experience, I bet that > trace_benchmark.c won't be the only place needing help. Perhaps, still think this is a special case. That said, perhaps cond_resched isn't done in critical locations as it's a place that is explicitly stating that it's OK to schedule. -- Steve