From 8ec55b8132b39da9d2e863e546a0e8c040f4e93f Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 31 May 2011 16:59:16 +0200
Subject: [PATCH 088/365] sched: Move task_struct cleanup to RCU

__put_task_struct() does quite some expensive work. We don't want to
burden random tasks with that.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/sched.h | 13 +++++++++++++
 kernel/fork.c         | 15 ++++++++++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3374ce3c5208..f4d37625f2d1 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1832,6 +1832,9 @@ struct task_struct {
 	unsigned int	sequential_io;
 	unsigned int	sequential_io_avg;
 #endif
+#ifdef CONFIG_PREEMPT_RT_BASE
+	struct rcu_head put_rcu;
+#endif
 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
 	unsigned long	task_state_change;
 #endif
@@ -2041,6 +2044,15 @@ extern struct pid *cad_pid;
 extern void free_task(struct task_struct *tsk);
 #define get_task_struct(tsk) do { atomic_inc(&(tsk)->usage); } while(0)
 
+#ifdef CONFIG_PREEMPT_RT_BASE
+extern void __put_task_struct_cb(struct rcu_head *rhp);
+
+static inline void put_task_struct(struct task_struct *t)
+{
+	if (atomic_dec_and_test(&t->usage))
+		call_rcu(&t->put_rcu, __put_task_struct_cb);
+}
+#else
 extern void __put_task_struct(struct task_struct *t);
 
 static inline void put_task_struct(struct task_struct *t)
@@ -2048,6 +2060,7 @@ static inline void put_task_struct(struct task_struct *t)
 	if (atomic_dec_and_test(&t->usage))
 		__put_task_struct(t);
 }
+#endif
 
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
 extern void task_cputime(struct task_struct *t,
diff --git a/kernel/fork.c b/kernel/fork.c
index 3256c9e98db5..39cf90f0ea3b 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -244,7 +244,9 @@ static inline void put_signal_struct(struct signal_struct *sig)
 	if (atomic_dec_and_test(&sig->sigcnt))
 		free_signal_struct(sig);
 }
-
+#ifdef CONFIG_PREEMPT_RT_BASE
+static
+#endif
 void __put_task_struct(struct task_struct *tsk)
 {
 	WARN_ON(!tsk->exit_state);
@@ -261,7 +263,18 @@ void __put_task_struct(struct task_struct *tsk)
 	if (!profile_handoff_task(tsk))
 		free_task(tsk);
 }
+#ifndef CONFIG_PREEMPT_RT_BASE
 EXPORT_SYMBOL_GPL(__put_task_struct);
+#else
+void __put_task_struct_cb(struct rcu_head *rhp)
+{
+	struct task_struct *tsk = container_of(rhp, struct task_struct, put_rcu);
+
+	__put_task_struct(tsk);
+
+}
+EXPORT_SYMBOL_GPL(__put_task_struct_cb);
+#endif
 
 void __init __weak arch_task_cache_init(void) { }
 
-- 
2.10.2

