From 176f8f7a52cc6d09d686f0d900abda6942a52fbb Mon Sep 17 00:00:00 2001
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
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 <paulmck@linux.vnet.ibm.com>
---
 include/linux/sched.h | 2 ++
 1 file changed, 2 insertions(+)

(limited to 'include/linux/sched.h')

diff --git a/include/linux/sched.h b/include/linux/sched.h
index eaacac4ae77..ec8b34722bc 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1274,6 +1274,7 @@ struct task_struct {
 	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 @@ static inline void rcu_copy_process(struct task_struct *p)
 #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 */
 }
 
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