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 D9606C433F5 for ; Thu, 30 Aug 2018 01:56:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7193120661 for ; Thu, 30 Aug 2018 01:56:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7193120661 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 S1727352AbeH3F4D (ORCPT ); Thu, 30 Aug 2018 01:56:03 -0400 Received: from mail.kernel.org ([198.145.29.99]:43068 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726169AbeH3F4C (ORCPT ); Thu, 30 Aug 2018 01:56:02 -0400 Received: from vmware.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 10D1A20647; Thu, 30 Aug 2018 01:56:17 +0000 (UTC) Date: Wed, 29 Aug 2018 21:56:16 -0400 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, joel@joelfernandes.org, Tejun Heo Subject: Re: [PATCH tip/core/rcu 3/3] srcu: Make early-boot call_srcu() reuse workqueue lists Message-ID: <20180829215616.1c10e476@vmware.local.home> In-Reply-To: <20180829212313.22903-3-paulmck@linux.vnet.ibm.com> References: <20180829212036.GA22033@linux.vnet.ibm.com> <20180829212313.22903-3-paulmck@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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 29 Aug 2018 14:23:13 -0700 "Paul E. McKenney" wrote: > Allocating a list_head structure that is almost never used, and, when > used, is used only during early boot (rcu_init() and earlier), is a bit > wasteful. This commit therefore eliminates that list_head in favor of > the one in the work_struct structure. This is safe because the work_struct > structure cannot be used until after rcu_init() returns. > > Reported-by: Steven Rostedt > Signed-off-by: Paul E. McKenney > Cc: Tejun Heo > Cc: Lai Jiangshan > --- > include/linux/srcutiny.h | 2 -- > include/linux/srcutree.h | 3 +-- > kernel/rcu/srcutiny.c | 10 +++++----- > kernel/rcu/srcutree.c | 11 +++++------ > 4 files changed, 11 insertions(+), 15 deletions(-) > > diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h > index 2b5c0822e683..f41d2fb09f87 100644 > --- a/include/linux/srcutiny.h > +++ b/include/linux/srcutiny.h > @@ -36,7 +36,6 @@ struct srcu_struct { > struct rcu_head *srcu_cb_head; /* Pending callbacks: Head. */ > struct rcu_head **srcu_cb_tail; /* Pending callbacks: Tail. */ > struct work_struct srcu_work; /* For driving grace periods. */ > - struct list_head srcu_boot_entry; /* Early-boot callbacks. */ > #ifdef CONFIG_DEBUG_LOCK_ALLOC > struct lockdep_map dep_map; > #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ > @@ -49,7 +48,6 @@ void srcu_drive_gp(struct work_struct *wp); > .srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \ > .srcu_cb_tail = &name.srcu_cb_head, \ > .srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp), \ > - .srcu_boot_entry = LIST_HEAD_INIT(name.srcu_boot_entry), \ > __SRCU_DEP_MAP_INIT(name) \ > } > > diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h > index 9cfa4610113a..0ae91b3a7406 100644 > --- a/include/linux/srcutree.h > +++ b/include/linux/srcutree.h > @@ -94,7 +94,6 @@ struct srcu_struct { > /* callback for the barrier */ > /* operation. */ > struct delayed_work work; > - struct list_head srcu_boot_entry; /* Early-boot callbacks. */ > #ifdef CONFIG_DEBUG_LOCK_ALLOC > struct lockdep_map dep_map; > #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ > @@ -110,7 +109,7 @@ struct srcu_struct { > .sda = &pcpu_name, \ > .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ > .srcu_gp_seq_needed = -1UL, \ > - .srcu_boot_entry = LIST_HEAD_INIT(name.srcu_boot_entry), \ > + .work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0), \ Thanks! -- Steve > __SRCU_DEP_MAP_INIT(name) \ > } > > diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c > index d233f0c63f6f..b46e6683f8c9 100644 > --- a/kernel/rcu/srcutiny.c > +++ b/kernel/rcu/srcutiny.c > @@ -48,7 +48,7 @@ static int init_srcu_struct_fields(struct srcu_struct *sp) > sp->srcu_gp_waiting = false; > sp->srcu_idx = 0; > INIT_WORK(&sp->srcu_work, srcu_drive_gp); > - INIT_LIST_HEAD(&sp->srcu_boot_entry); > + INIT_LIST_HEAD(&sp->srcu_work.entry); > return 0; > } > > @@ -185,8 +185,8 @@ void call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, > if (!READ_ONCE(sp->srcu_gp_running)) { > if (likely(srcu_init_done)) > schedule_work(&sp->srcu_work); > - else if (list_empty(&sp->srcu_boot_entry)) > - list_add(&sp->srcu_boot_entry, &srcu_boot_list); > + else if (list_empty(&sp->srcu_work.entry)) > + list_add(&sp->srcu_work.entry, &srcu_boot_list); > } > } > EXPORT_SYMBOL_GPL(call_srcu); > @@ -224,8 +224,8 @@ void __init srcu_init(void) > srcu_init_done = true; > while (!list_empty(&srcu_boot_list)) { > sp = list_first_entry(&srcu_boot_list, > - struct srcu_struct, srcu_boot_entry); > - list_del_init(&sp->srcu_boot_entry); > + struct srcu_struct, srcu_work.entry); > + list_del_init(&sp->srcu_work.entry); > schedule_work(&sp->srcu_work); > } > } > diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c > index e79c1929328f..36a2857c84e0 100644 > --- a/kernel/rcu/srcutree.c > +++ b/kernel/rcu/srcutree.c > @@ -186,7 +186,6 @@ static int init_srcu_struct_fields(struct srcu_struct *sp, bool is_static) > mutex_init(&sp->srcu_barrier_mutex); > atomic_set(&sp->srcu_barrier_cpu_cnt, 0); > INIT_DELAYED_WORK(&sp->work, process_srcu); > - INIT_LIST_HEAD(&sp->srcu_boot_entry); > if (!is_static) > sp->sda = alloc_percpu(struct srcu_data); > init_srcu_struct_nodes(sp, is_static); > @@ -709,8 +708,8 @@ static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp, > if (likely(srcu_init_done)) > queue_delayed_work(rcu_gp_wq, &sp->work, > srcu_get_delay(sp)); > - else if (list_empty(&sp->srcu_boot_entry)) > - list_add(&sp->srcu_boot_entry, &srcu_boot_list); > + else if (list_empty(&sp->work.work.entry)) > + list_add(&sp->work.work.entry, &srcu_boot_list); > } > spin_unlock_irqrestore_rcu_node(sp, flags); > } > @@ -1324,10 +1323,10 @@ void __init srcu_init(void) > > srcu_init_done = true; > while (!list_empty(&srcu_boot_list)) { > - sp = list_first_entry(&srcu_boot_list, > - struct srcu_struct, srcu_boot_entry); > + sp = list_first_entry(&srcu_boot_list, struct srcu_struct, > + work.work.entry); > check_init_srcu_struct(sp); > - list_del_init(&sp->srcu_boot_entry); > + list_del_init(&sp->work.work.entry); > queue_work(rcu_gp_wq, &sp->work.work); > } > }