From 176f8f7a52cc6d09d686f0d900abda6942a52fbb Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 4 Aug 2014 17:43:50 -0700 Subject: rcu: Make TASKS_RCU handle nohz_full= CPUs Currently TASKS_RCU would ignore a CPU running a task in nohz_full= usermode execution. There would be neither a context switch nor a scheduling-clock interrupt to tell TASKS_RCU that the task in question had passed through a quiescent state. The grace period would therefore extend indefinitely. This commit therefore makes RCU's dyntick-idle subsystem record the task_struct structure of the task that is running in dyntick-idle mode on each CPU. The TASKS_RCU grace period can then access this information and record a quiescent state on behalf of any CPU running in dyntick-idle usermode. Signed-off-by: Paul E. McKenney --- kernel/rcu/update.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'kernel/rcu/update.c') diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index e1d71741958f..2658de4a5975 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -463,7 +463,9 @@ static void check_holdout_task(struct task_struct *t, { if (!ACCESS_ONCE(t->rcu_tasks_holdout) || t->rcu_tasks_nvcsw != ACCESS_ONCE(t->nvcsw) || - !ACCESS_ONCE(t->on_rq)) { + !ACCESS_ONCE(t->on_rq) || + (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); put_task_struct(t); -- cgit v1.2.3