From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2E553C5CFEB for ; Wed, 11 Jul 2018 13:06:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CA6FE20B6F for ; Wed, 11 Jul 2018 13:06:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CA6FE20B6F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387762AbeGKNLI (ORCPT ); Wed, 11 Jul 2018 09:11:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:45140 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732420AbeGKNLI (ORCPT ); Wed, 11 Jul 2018 09:11:08 -0400 Received: from gandalf.local.home (cpe-66-24-56-78.stny.res.rr.com [66.24.56.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D78082089B; Wed, 11 Jul 2018 13:06:50 +0000 (UTC) Date: Wed, 11 Jul 2018 09:06:49 -0400 From: Steven Rostedt To: Peter Zijlstra Cc: Joel Fernandes , linux-kernel@vger.kernel.org, Boqun Feng , Byungchul Park , Ingo Molnar , Julia Cartwright , linux-kselftest@vger.kernel.org, Masami Hiramatsu , Mathieu Desnoyers , Namhyung Kim , Paul McKenney , Thomas Glexiner , Tom Zanussi Subject: Re: [PATCH v9 4/7] tracepoint: Make rcuidle tracepoint callers use SRCU Message-ID: <20180711090649.68af40f9@gandalf.local.home> In-Reply-To: <20180711125647.GG2476@hirez.programming.kicks-ass.net> References: <20180628182149.226164-1-joel@joelfernandes.org> <20180628182149.226164-5-joel@joelfernandes.org> <20180711125647.GG2476@hirez.programming.kicks-ass.net> X-Mailer: Claws Mail 3.16.0 (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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 11 Jul 2018 14:56:47 +0200 Peter Zijlstra wrote: > On Thu, Jun 28, 2018 at 11:21:46AM -0700, Joel Fernandes wrote: > > static inline void tracepoint_synchronize_unregister(void) > > { > > + synchronize_srcu(&tracepoint_srcu); > > synchronize_sched(); > > } > > Given you below do call_rcu_sched() and then call_srcu(), isn't the > above the wrong way around? Good catch! release_probes() call_rcu_sched() ---> rcu_free_old_probes() queued tracepoint_synchronize_unregister() synchronize_srcu(&tracepoint_srcu); < finishes right away > synchronize_sched() --> rcu_free_old_probes() --> srcu_free_old_probes() queued Here tracepoint_synchronize_unregister() returned before the srcu portion ran. > > Also, does the above want to be barrier instead of synchronize, so as to > guarantee completion of the callbacks. Not sure what you mean here. -- Steve > > > +static void srcu_free_old_probes(struct rcu_head *head) > > { > > kfree(container_of(head, struct tp_probes, rcu)); > > } > > > > +static void rcu_free_old_probes(struct rcu_head *head) > > +{ > > + call_srcu(&tracepoint_srcu, head, srcu_free_old_probes); > > +} > > + > > static inline void release_probes(struct tracepoint_func *old) > > { > > if (old) { > > struct tp_probes *tp_probes = container_of(old, > > struct tp_probes, probes[0]); > > + /* > > + * Tracepoint probes are protected by both sched RCU and SRCU, > > + * by calling the SRCU callback in the sched RCU callback we > > + * cover both cases. So let us chain the SRCU and sched RCU > > + * callbacks to wait for both grace periods. > > + */ > > call_rcu_sched(&tp_probes->rcu, rcu_free_old_probes); > > } > > } From mboxrd@z Thu Jan 1 00:00:00 1970 From: rostedt at goodmis.org (Steven Rostedt) Date: Wed, 11 Jul 2018 09:06:49 -0400 Subject: [PATCH v9 4/7] tracepoint: Make rcuidle tracepoint callers use SRCU In-Reply-To: <20180711125647.GG2476@hirez.programming.kicks-ass.net> References: <20180628182149.226164-1-joel@joelfernandes.org> <20180628182149.226164-5-joel@joelfernandes.org> <20180711125647.GG2476@hirez.programming.kicks-ass.net> Message-ID: <20180711090649.68af40f9@gandalf.local.home> On Wed, 11 Jul 2018 14:56:47 +0200 Peter Zijlstra wrote: > On Thu, Jun 28, 2018 at 11:21:46AM -0700, Joel Fernandes wrote: > > static inline void tracepoint_synchronize_unregister(void) > > { > > + synchronize_srcu(&tracepoint_srcu); > > synchronize_sched(); > > } > > Given you below do call_rcu_sched() and then call_srcu(), isn't the > above the wrong way around? Good catch! release_probes() call_rcu_sched() ---> rcu_free_old_probes() queued tracepoint_synchronize_unregister() synchronize_srcu(&tracepoint_srcu); < finishes right away > synchronize_sched() --> rcu_free_old_probes() --> srcu_free_old_probes() queued Here tracepoint_synchronize_unregister() returned before the srcu portion ran. > > Also, does the above want to be barrier instead of synchronize, so as to > guarantee completion of the callbacks. Not sure what you mean here. -- Steve > > > +static void srcu_free_old_probes(struct rcu_head *head) > > { > > kfree(container_of(head, struct tp_probes, rcu)); > > } > > > > +static void rcu_free_old_probes(struct rcu_head *head) > > +{ > > + call_srcu(&tracepoint_srcu, head, srcu_free_old_probes); > > +} > > + > > static inline void release_probes(struct tracepoint_func *old) > > { > > if (old) { > > struct tp_probes *tp_probes = container_of(old, > > struct tp_probes, probes[0]); > > + /* > > + * Tracepoint probes are protected by both sched RCU and SRCU, > > + * by calling the SRCU callback in the sched RCU callback we > > + * cover both cases. So let us chain the SRCU and sched RCU > > + * callbacks to wait for both grace periods. > > + */ > > call_rcu_sched(&tp_probes->rcu, rcu_free_old_probes); > > } > > } -- To unsubscribe from this list: send the line "unsubscribe linux-kselftest" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html From mboxrd@z Thu Jan 1 00:00:00 1970 From: rostedt@goodmis.org (Steven Rostedt) Date: Wed, 11 Jul 2018 09:06:49 -0400 Subject: [PATCH v9 4/7] tracepoint: Make rcuidle tracepoint callers use SRCU In-Reply-To: <20180711125647.GG2476@hirez.programming.kicks-ass.net> References: <20180628182149.226164-1-joel@joelfernandes.org> <20180628182149.226164-5-joel@joelfernandes.org> <20180711125647.GG2476@hirez.programming.kicks-ass.net> Message-ID: <20180711090649.68af40f9@gandalf.local.home> Content-Type: text/plain; charset="UTF-8" Message-ID: <20180711130649.zX6sIBwwAA-0Tt_cLpKppbpmeVIuzRZMq7pOQfXLJ_I@z> On Wed, 11 Jul 2018 14:56:47 +0200 Peter Zijlstra wrote: > On Thu, Jun 28, 2018@11:21:46AM -0700, Joel Fernandes wrote: > > static inline void tracepoint_synchronize_unregister(void) > > { > > + synchronize_srcu(&tracepoint_srcu); > > synchronize_sched(); > > } > > Given you below do call_rcu_sched() and then call_srcu(), isn't the > above the wrong way around? Good catch! release_probes() call_rcu_sched() ---> rcu_free_old_probes() queued tracepoint_synchronize_unregister() synchronize_srcu(&tracepoint_srcu); < finishes right away > synchronize_sched() --> rcu_free_old_probes() --> srcu_free_old_probes() queued Here tracepoint_synchronize_unregister() returned before the srcu portion ran. > > Also, does the above want to be barrier instead of synchronize, so as to > guarantee completion of the callbacks. Not sure what you mean here. -- Steve > > > +static void srcu_free_old_probes(struct rcu_head *head) > > { > > kfree(container_of(head, struct tp_probes, rcu)); > > } > > > > +static void rcu_free_old_probes(struct rcu_head *head) > > +{ > > + call_srcu(&tracepoint_srcu, head, srcu_free_old_probes); > > +} > > + > > static inline void release_probes(struct tracepoint_func *old) > > { > > if (old) { > > struct tp_probes *tp_probes = container_of(old, > > struct tp_probes, probes[0]); > > + /* > > + * Tracepoint probes are protected by both sched RCU and SRCU, > > + * by calling the SRCU callback in the sched RCU callback we > > + * cover both cases. So let us chain the SRCU and sched RCU > > + * callbacks to wait for both grace periods. > > + */ > > call_rcu_sched(&tp_probes->rcu, rcu_free_old_probes); > > } > > } -- To unsubscribe from this list: send the line "unsubscribe linux-kselftest" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html