patches/sched-delay-put-task.patch

Subject: sched: Move task_struct cleanup to RCU
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 31 May 2011 16:59:16 +0200

__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(-)

--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1831,6 +1831,9 @@ 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
@@ -2040,6 +2043,15 @@ 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)
@@ -2047,6 +2059,7 @@ static inline void put_task_struct(struc
 	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,
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -244,7 +244,9 @@ static inline void put_signal_struct(str
 	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_struc
 	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) { }