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rcu: Shrink TINY_RCU by moving exit_rcu() 

Now that TINY_PREEMPT_RCU is no more, exit_rcu() is always an empty
function.  But if TINY_RCU is going to have an empty function, it should
be in include/linux/rcutiny.h, where it does not bloat the kernel.
This commit therefore moves exit_rcu() out of kernel/rcupdate.c to
kernel/rcutree_plugin.h, and places a static inline empty function in
include/linux/rcutiny.h in order to shrink TINY_RCU a bit.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit is contained in:
Paul E. McKenney 2013-04-11 10:15:52 -07:00
parent 7807acdb6b
commit 2439b696cb
5 changed files with 33 additions and 27 deletions
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2
include/linux/rcupdate.h
View File

@ -240,8 +240,6 @@ static inline void rcu_user_hooks_switch(struct task_struct *prev,
struct task_struct *next) { }
#endif /* CONFIG_RCU_USER_QS */
extern void exit_rcu(void);
/**
* RCU_NONIDLE - Indicate idle-loop code that needs RCU readers
* @a: Code that RCU needs to pay attention to.

4
include/linux/rcutiny.h
View File

@ -119,6 +119,10 @@ static inline void rcu_cpu_stall_reset(void)
{
}
static inline void exit_rcu(void)
{
}
#ifdef CONFIG_DEBUG_LOCK_ALLOC
extern int rcu_scheduler_active __read_mostly;
extern void rcu_scheduler_starting(void);

2
include/linux/rcutree.h
View File

@ -85,6 +85,8 @@ extern void rcu_force_quiescent_state(void);
extern void rcu_bh_force_quiescent_state(void);
extern void rcu_sched_force_quiescent_state(void);
extern void exit_rcu(void);
extern void rcu_scheduler_starting(void);
extern int rcu_scheduler_active __read_mostly;

26
kernel/rcupdate.c
View File

@ -104,31 +104,7 @@ void __rcu_read_unlock(void)
}
EXPORT_SYMBOL_GPL(__rcu_read_unlock);
/*
* Check for a task exiting while in a preemptible-RCU read-side
* critical section, clean up if so. No need to issue warnings,
* as debug_check_no_locks_held() already does this if lockdep
* is enabled.
*/
void exit_rcu(void)
{
struct task_struct *t = current;
if (likely(list_empty(&current->rcu_node_entry)))
return;
t->rcu_read_lock_nesting = 1;
barrier();
t->rcu_read_unlock_special = RCU_READ_UNLOCK_BLOCKED;
__rcu_read_unlock();
}
#else /* #ifdef CONFIG_PREEMPT_RCU */
void exit_rcu(void)
{
}
#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
#endif /* #ifdef CONFIG_PREEMPT_RCU */
#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key rcu_lock_key;

26
kernel/rcutree_plugin.h
View File

@ -932,6 +932,24 @@ static void __init __rcu_init_preempt(void)
rcu_init_one(&rcu_preempt_state, &rcu_preempt_data);
}
/*
* Check for a task exiting while in a preemptible-RCU read-side
* critical section, clean up if so. No need to issue warnings,
* as debug_check_no_locks_held() already does this if lockdep
* is enabled.
*/
void exit_rcu(void)
{
struct task_struct *t = current;
if (likely(list_empty(&current->rcu_node_entry)))
return;
t->rcu_read_lock_nesting = 1;
barrier();
t->rcu_read_unlock_special = RCU_READ_UNLOCK_BLOCKED;
__rcu_read_unlock();
}
#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
static struct rcu_state *rcu_state = &rcu_sched_state;
@ -1100,6 +1118,14 @@ static void __init __rcu_init_preempt(void)
{
}
/*
* Because preemptible RCU does not exist, tasks cannot possibly exit
* while in preemptible RCU read-side critical sections.
*/
void exit_rcu(void)
{
}
#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
#ifdef CONFIG_RCU_BOOST