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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2014-08-04 17:43:50 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2014-09-07 16:27:30 -0700
commit176f8f7a52cc6d09d686f0d900abda6942a52fbb (patch)
treebd3d6a8f21e576a94d1e1812c5c5317f62d1c96d /kernel/rcu/update.c
parent84a8f446ffd70c2799a96268aaa4d47c22a83ff0 (diff)
downloadlinux-sh-176f8f7a52cc6d09d686f0d900abda6942a52fbb.tar.gz
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 <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu/update.c')
-rw-r--r--kernel/rcu/update.c4
1 files changed, 3 insertions, 1 deletions
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);