From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754828AbaH1TVc (ORCPT ); Thu, 28 Aug 2014 15:21:32 -0400 Received: from e39.co.us.ibm.com ([32.97.110.160]:46681 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753891AbaH1TUU (ORCPT ); Thu, 28 Aug 2014 15:20:20 -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 v7 tip/core/rcu 13/17] rcu: Make rcu_tasks_kthread()'s GP-wait loop allow preemption Date: Thu, 28 Aug 2014 12:20:04 -0700 Message-Id: <1409253608-32538-13-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1409253608-32538-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20140828191929.GA31795@linux.vnet.ibm.com> <1409253608-32538-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14082819-9332-0000-0000-000001D6E9CC 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 2658de4a5975..f86d1ae50005 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -467,7 +467,7 @@ 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; } @@ -573,6 +573,7 @@ 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); @@ -582,11 +583,11 @@ 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