From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751708AbaHOQ3B (ORCPT ); Fri, 15 Aug 2014 12:29:01 -0400 Received: from e36.co.us.ibm.com ([32.97.110.154]:52374 "EHLO e36.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751379AbaHOQ26 (ORCPT ); Fri, 15 Aug 2014 12:28:58 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, "Paul E. McKenney" Subject: [PATCH v6 tip/core/rcu 13/17] rcu: Make rcu_tasks_kthread()'s GP-wait loop allow preemption Date: Fri, 15 Aug 2014 09:28:41 -0700 Message-Id: <1408120125-30479-13-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1408120125-30479-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20140815162820.GA28967@linux.vnet.ibm.com> <1408120125-30479-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14081516-3532-0000-0000-000003E07BBA Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" The grace-period-wait loop in rcu_tasks_kthread() is under (unnecessary) RCU protection, and therefore has no preemption points in a PREEMPT=n kernel. This commit therefore removes the RCU protection and inserts cond_resched(). Reported-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney --- kernel/rcu/update.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index 90239bc0a0b8..2130f0597771 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -470,7 +470,7 @@ static void check_holdout_task(struct task_struct *t, (IS_ENABLED(CONFIG_NO_HZ_FULL) && !is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) { ACCESS_ONCE(t->rcu_tasks_holdout) = false; - list_del_rcu(&t->rcu_tasks_holdout_list); + list_del_init(&t->rcu_tasks_holdout_list); put_task_struct(t); return; } @@ -576,6 +576,7 @@ static int __noreturn rcu_tasks_kthread(void *arg) bool firstreport; bool needreport; int rtst; + struct task_struct *t1; schedule_timeout_interruptible(HZ); rtst = ACCESS_ONCE(rcu_task_stall_timeout); @@ -585,11 +586,11 @@ static int __noreturn rcu_tasks_kthread(void *arg) lastreport = jiffies; firstreport = true; WARN_ON(signal_pending(current)); - rcu_read_lock(); - list_for_each_entry_rcu(t, &rcu_tasks_holdouts, - rcu_tasks_holdout_list) + list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts, + rcu_tasks_holdout_list) { check_holdout_task(t, needreport, &firstreport); - rcu_read_unlock(); + cond_resched(); + } } /* -- 1.8.1.5