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>
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index dffd925..03b2748 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -121,7 +121,8 @@
#define INIT_TASK_RCU_TASKS(tsk) \
.rcu_tasks_holdout = false, \
.rcu_tasks_holdout_list = \
- LIST_HEAD_INIT(tsk.rcu_tasks_holdout_list),
+ LIST_HEAD_INIT(tsk.rcu_tasks_holdout_list), \
+ .rcu_tasks_idle_cpu = -1,
#else
#define INIT_TASK_RCU_TASKS(tsk)
#endif