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/sched.h b/include/linux/sched.h
index eaacac4..ec8b347 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1274,6 +1274,7 @@
unsigned long rcu_tasks_nvcsw;
bool rcu_tasks_holdout;
struct list_head rcu_tasks_holdout_list;
+ int rcu_tasks_idle_cpu;
#endif /* #ifdef CONFIG_TASKS_RCU */
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
@@ -2020,6 +2021,7 @@
#ifdef CONFIG_TASKS_RCU
p->rcu_tasks_holdout = false;
INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
+ p->rcu_tasks_idle_cpu = -1;
#endif /* #ifdef CONFIG_TASKS_RCU */
}