From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751982AbeBZSWf (ORCPT ); Mon, 26 Feb 2018 13:22:35 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:53800 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751885AbeBZSWc (ORCPT ); Mon, 26 Feb 2018 13:22:32 -0500 Date: Mon, 26 Feb 2018 10:22:54 -0800 From: "Paul E. McKenney" To: Steven Rostedt Cc: Byungchul Park , jiangshanlai@gmail.com, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, linux-kernel@vger.kernel.org, kernel-team@lge.com Subject: Re: [PATCH] rcu: Remove the unnecessary separate function, rcu_preempt_do_callback() Reply-To: paulmck@linux.vnet.ibm.com References: <1519621896-8786-1-git-send-email-byungchul.park@lge.com> <20180226121514.122669b9@vmware.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180226121514.122669b9@vmware.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 18022618-0008-0000-0000-000002DB888A X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00008601; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000254; SDB=6.00995460; UDB=6.00505993; IPR=6.00774790; MB=3.00019750; MTD=3.00000008; XFM=3.00000015; UTC=2018-02-26 18:22:28 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18022618-0009-0000-0000-000038647E52 Message-Id: <20180226182254.GU2855@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-02-26_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1802260235 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 26, 2018 at 12:15:14PM -0500, Steven Rostedt wrote: > On Mon, 26 Feb 2018 14:11:36 +0900 > Byungchul Park wrote: > > > rcu_preemptp_do_callback() was introduced in commit 09223371dea(rcu: > > Use softirq to address performance regression), where it had to be > > distinguished between in the case CONFIG_TREE_PREEMPT_RCU is set and > > it's not. > > > > Now that the code was cleaned up so that rcu_preemt_do_callback() is > > only called in rcu_kthread_do_work() in the same file, tree_plugin.h, > > we don't have to keep the separate function anymore. Remove it for a > > better readability. > > Looks good to me (looks like commit f8b7fc6b51 "rcu: use softirq > instead of kthreads except when RCU_BOOST=y" cleaned up the ifdefs and > removed the requirement). > > Reviewed-by: Steven Rostedt (VMware) Thank you both! I have queued a slightly modified patch for testing and further review. Please see below and let me know if I messed something up. Thanx, Paul ------------------------------------------------------------------------ commit b8a3012ddba397d4a18d9fd4a00432f8c2626bd6 Author: Byungchul Park Date: Mon Feb 26 14:11:36 2018 +0900 rcu: Inline rcu_preempt_do_callback() into its sole caller The rcu_preempt_do_callbacks() function was introduced in commit 09223371dea(rcu: Use softirq to address performance regression), where it was necessary to handle kernel builds both containing and not containing RCU-preempt. Since then, various changes (most notably f8b7fc6b51 ("rcu: use softirq instead of kthreads except when RCU_BOOST=y")) have resulted in this function being invoked only from rcu_kthread_do_work(), which is present only in kernels containing RCU-preempt, which in turn means that the rcu_preempt_do_callbacks() function is no longer needed. This commit therefore inlines rcu_preempt_do_callbacks() into its sole remaining caller and also removes the rcu_state_p and rcu_data_p indirection for added clarity. Signed-off-by: Byungchul Park Reviewed-by: Steven Rostedt (VMware) [ paulmck: Remove the rcu_state_p and rcu_data_p indirection. ] diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index dc6f2319fc21..9dd0ea77faed 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -449,7 +449,6 @@ static void rcu_preempt_boost_start_gp(struct rcu_node *rnp); static void invoke_rcu_callbacks_kthread(void); static bool rcu_is_callbacks_kthread(void); #ifdef CONFIG_RCU_BOOST -static void rcu_preempt_do_callbacks(void); static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp, struct rcu_node *rnp); #endif /* #ifdef CONFIG_RCU_BOOST */ diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 26d7a31e81cb..b0d7f9ba6bf2 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -686,15 +686,6 @@ static void rcu_preempt_check_callbacks(void) t->rcu_read_unlock_special.b.need_qs = true; } -#ifdef CONFIG_RCU_BOOST - -static void rcu_preempt_do_callbacks(void) -{ - rcu_do_batch(rcu_state_p, this_cpu_ptr(rcu_data_p)); -} - -#endif /* #ifdef CONFIG_RCU_BOOST */ - /** * call_rcu() - Queue an RCU callback for invocation after a grace period. * @head: structure to be used for queueing the RCU updates. @@ -1170,7 +1161,7 @@ static void rcu_kthread_do_work(void) { rcu_do_batch(&rcu_sched_state, this_cpu_ptr(&rcu_sched_data)); rcu_do_batch(&rcu_bh_state, this_cpu_ptr(&rcu_bh_data)); - rcu_preempt_do_callbacks(); + rcu_do_batch(&rcu_preempt_state, this_cpu_ptr(&rcu_preempt_data)); } static void rcu_cpu_kthread_setup(unsigned int cpu)