From 8f20a5e83d2c5d0e126a2fc9bca67f7430dac907 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 5 Aug 2014 05:10:24 -0700 Subject: [PATCH] rcu: Make rcu_tasks_kthread()'s GP-wait loop allow preemption 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(); + } } /* -- 2.20.1