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Subject: sched: Move task_struct cleanup to RCU
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 31 May 2011 16:59:16 +0200
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.9/older/patches-4.9.20-rt16.tar.xz
__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
@@ -1962,6 +1962,9 @@ 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
@@ -2219,6 +2222,15 @@ 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)
@@ -2226,6 +2238,7 @@ static inline void put_task_struct(struc
if (atomic_dec_and_test(&t->usage))
__put_task_struct(t);
}
+#endif
struct task_struct *task_rcu_dereference(struct task_struct **ptask);
struct task_struct *try_get_task_struct(struct task_struct **ptask);
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -376,7 +376,9 @@ 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);
@@ -393,7 +395,18 @@ 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) { }
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