From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751907AbdJEQDn (ORCPT ); Thu, 5 Oct 2017 12:03:43 -0400 Received: from mail.efficios.com ([167.114.142.141]:51656 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751334AbdJEQDk (ORCPT ); Thu, 5 Oct 2017 12:03:40 -0400 Date: Thu, 5 Oct 2017 16:05:10 +0000 (UTC) From: Mathieu Desnoyers To: Peter Zijlstra Cc: "Paul E. McKenney" , linux-kernel , Ingo Molnar , Lai Jiangshan , dipankar , Andrew Morton , Josh Triplett , Thomas Gleixner , rostedt , David Howells , Eric Dumazet , fweisbec , Oleg Nesterov , Boqun Feng , Andrew Hunter , maged michael , gromer , Avi Kivity , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Dave Watson , Alan Stern , Will Deacon , Andy Lutomirski , Ingo Molnar , Alexander Viro , Nicholas Piggin , linuxppc-dev , linux-arch Message-ID: <449773494.31740.1507219510868.JavaMail.zimbra@efficios.com> In-Reply-To: <20171005122458.zfl2vl7h4jiu67ms@hirez.programming.kicks-ass.net> References: <20171004213734.GA11463@linux.vnet.ibm.com> <1507153075-12345-1-git-send-email-paulmck@linux.vnet.ibm.com> <20171005121250.prr5ff5kf3lxq6hx@hirez.programming.kicks-ass.net> <20171005122458.zfl2vl7h4jiu67ms@hirez.programming.kicks-ass.net> Subject: Re: [PATCH tip/core/rcu 1/3] membarrier: Provide register expedited private command MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [167.114.142.141] X-Mailer: Zimbra 8.7.11_GA_1854 (ZimbraWebClient - FF52 (Linux)/8.7.11_GA_1854) Thread-Topic: membarrier: Provide register expedited private command Thread-Index: lm7Qoyu6ZSJ9OC+5Dlijaf9iSgxRIQ== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- On Oct 5, 2017, at 8:24 AM, Peter Zijlstra peterz@infradead.org wrote: > On Thu, Oct 05, 2017 at 02:12:50PM +0200, Peter Zijlstra wrote: >> On Wed, Oct 04, 2017 at 02:37:53PM -0700, Paul E. McKenney wrote: >> > diff --git a/arch/powerpc/kernel/membarrier.c b/arch/powerpc/kernel/membarrier.c >> > new file mode 100644 >> > index 000000000000..b0d79a5f5981 >> > --- /dev/null >> > +++ b/arch/powerpc/kernel/membarrier.c >> > @@ -0,0 +1,45 @@ >> >> > +void membarrier_arch_register_private_expedited(struct task_struct *p) >> > +{ >> > + struct task_struct *t; >> > + >> > + if (get_nr_threads(p) == 1) { >> > + set_thread_flag(TIF_MEMBARRIER_PRIVATE_EXPEDITED); >> > + return; >> > + } >> > + /* >> > + * Coherence of TIF_MEMBARRIER_PRIVATE_EXPEDITED against thread >> > + * fork is protected by siglock. >> > + */ >> > + spin_lock(&p->sighand->siglock); >> > + for_each_thread(p, t) >> > + set_ti_thread_flag(task_thread_info(t), >> > + TIF_MEMBARRIER_PRIVATE_EXPEDITED); >> >> I'm not sure this works correctly vs CLONE_VM without CLONE_THREAD. > > Also, for easier reading I would suggest putting { } around the block. Will do, thanks, Mathieu > >> > + spin_unlock(&p->sighand->siglock); >> > + /* >> > + * Ensure all future scheduler executions will observe the new >> > + * thread flag state for this process. >> > + */ >> > + synchronize_sched(); >> >> This relies on the flag being read inside rq->lock, right? >> > > > +} -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com