From: "Paul E. McKenney" <paul...@linux.vnet.ibm.com>
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 <fweis...@gmail.com>
Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
---
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 a4140f25cf1a..2ae6fb8752d4 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) = 0;
- 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
--
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