diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 03cda7bed98587b128c5a9953316644a8debb4d2..7142ee3304ab6e1d6467743377182907968ac417 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -118,7 +118,6 @@ static inline int rcu_preempt_depth(void)
#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
/* Internal to kernel */
-extern void rcu_init(void);
extern void rcu_sched_qs(int cpu);
extern void rcu_bh_qs(int cpu);
extern void rcu_check_callbacks(int cpu, int user);
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 13877cb93a6000043f11a6704f2d90b0cc04552d..ea025a611fcc4eb2eb140b2ae92c681afcb899f7 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -27,7 +27,9 @@
#include <linux/cache.h>
-#define rcu_init_sched() do { } while (0)
+static inline void rcu_init(void)
+{
+}
#ifdef CONFIG_TINY_RCU
@@ -125,16 +127,12 @@ static inline void rcu_cpu_stall_reset(void)
}
#ifdef CONFIG_DEBUG_LOCK_ALLOC
-
extern int rcu_scheduler_active __read_mostly;
extern void rcu_scheduler_starting(void);
-
#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
-
static inline void rcu_scheduler_starting(void)
{
}
-
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
#endif /* __LINUX_RCUTINY_H */
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 95518e6287946177e0eceb5cbf201ebfcaf0e072..c0e96833aa734178bf123bb83ce81efa6ab6da36 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -30,6 +30,7 @@
#ifndef __LINUX_RCUTREE_H
#define __LINUX_RCUTREE_H
+extern void rcu_init(void);
extern void rcu_note_context_switch(int cpu);
extern int rcu_needs_cpu(int cpu);
extern void rcu_cpu_stall_reset(void);
diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index d806735342acb10bc3e3ae787e62ade34f1d5955..86eef29cdfb291f596bd5b83774a9d97b93ca554 100644
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -59,8 +59,15 @@ int rcu_scheduler_active __read_mostly;
EXPORT_SYMBOL_GPL(rcu_scheduler_active);
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+/* Controls for rcu_cbs() kthread, replacing RCU_SOFTIRQ used previously. */
+static struct task_struct *rcu_cbs_task;
+static DECLARE_WAIT_QUEUE_HEAD(rcu_cbs_wq);
+static unsigned long have_rcu_cbs;
+static void invoke_rcu_cbs(void);
+
/* Forward declarations for rcutiny_plugin.h. */
-static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp);
+static void rcu_process_callbacks(struct rcu_ctrlblk *rcp);
+static int rcu_cbs(void *arg);
static void __call_rcu(struct rcu_head *head,
void (*func)(struct rcu_head *rcu),
struct rcu_ctrlblk *rcp);
@@ -123,7 +130,7 @@ void rcu_sched_qs(int cpu)
{
if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
rcu_qsctr_help(&rcu_bh_ctrlblk))
- raise_softirq(RCU_SOFTIRQ);
+ invoke_rcu_cbs();
}
/*
@@ -132,7 +139,7 @@ void rcu_sched_qs(int cpu)
void rcu_bh_qs(int cpu)
{
if (rcu_qsctr_help(&rcu_bh_ctrlblk))
- raise_softirq(RCU_SOFTIRQ);
+ invoke_rcu_cbs();
}
/*
@@ -152,10 +159,10 @@ void rcu_check_callbacks(int cpu, int user)
}
/*
- * Helper function for rcu_process_callbacks() that operates on the
- * specified rcu_ctrlkblk structure.
+ * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure
+ * whose grace period has elapsed.
*/
-static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
+static void rcu_process_callbacks(struct rcu_ctrlblk *rcp)
{
struct rcu_head *next, *list;
unsigned long flags;
@@ -180,19 +187,52 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
next = list->next;
prefetch(next);
debug_rcu_head_unqueue(list);
+ local_bh_disable();
list->func(list);
+ local_bh_enable();
list = next;
}
}
/*
- * Invoke any callbacks whose grace period has completed.
+ * This kthread invokes RCU callbacks whose grace periods have
+ * elapsed. It is awakened as needed, and takes the place of the
+ * RCU_SOFTIRQ that was used previously for this purpose.
+ * This is a kthread, but it is never stopped, at least not until
+ * the system goes down.
+ */
+static int rcu_cbs(void *arg)
+{
+ unsigned long work;
+ unsigned long flags;
+
+ for (;;) {
+ wait_event(rcu_cbs_wq, have_rcu_cbs != 0);
+ local_irq_save(flags);
+ work = have_rcu_cbs;
+ have_rcu_cbs = 0;
+ local_irq_restore(flags);
+ if (work) {
+ rcu_process_callbacks(&rcu_sched_ctrlblk);
+ rcu_process_callbacks(&rcu_bh_ctrlblk);
+ rcu_preempt_process_callbacks();
+ }
+ }
+
+ return 0; /* Not reached, but needed to shut gcc up. */
+}
+
+/*
+ * Wake up rcu_cbs() to process callbacks now eligible for invocation.
*/
-static void rcu_process_callbacks(struct softirq_action *unused)
+static void invoke_rcu_cbs(void)
{
- __rcu_process_callbacks(&rcu_sched_ctrlblk);
- __rcu_process_callbacks(&rcu_bh_ctrlblk);
- rcu_preempt_process_callbacks();
+ unsigned long flags;
+
+ local_irq_save(flags);
+ have_rcu_cbs = 1;
+ wake_up(&rcu_cbs_wq);
+ local_irq_restore(flags);
}
/*
@@ -282,7 +322,12 @@ void rcu_barrier_sched(void)
}
EXPORT_SYMBOL_GPL(rcu_barrier_sched);
-void __init rcu_init(void)
+/*
+ * Spawn the kthread that invokes RCU callbacks.
+ */
+static int __init rcu_spawn_kthreads(void)
{
- open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
+ rcu_cbs_task = kthread_run(rcu_cbs, NULL, "rcu_cbs");
+ return 0;
}
+early_initcall(rcu_spawn_kthreads);
diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
index 6ceca4f745ffa1f4535c69467ea59704e2ddbe97..95f9239df5120581ed770dd76be8d15575c4d74c 100644
--- a/kernel/rcutiny_plugin.h
+++ b/kernel/rcutiny_plugin.h
@@ -22,6 +22,8 @@
* Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
*/
+#include <linux/kthread.h>
+
#ifdef CONFIG_TINY_PREEMPT_RCU
#include <linux/delay.h>
@@ -164,9 +166,9 @@ static void rcu_preempt_cpu_qs(void)
if (!rcu_preempt_blocked_readers_any())
rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.nexttail;
- /* If there are done callbacks, make RCU_SOFTIRQ process them. */
+ /* If there are done callbacks, cause them to be invoked. */
if (*rcu_preempt_ctrlblk.rcb.donetail != NULL)
- raise_softirq(RCU_SOFTIRQ);
+ invoke_rcu_cbs();
}
/*
@@ -374,7 +376,7 @@ static void rcu_preempt_check_callbacks(void)
rcu_preempt_cpu_qs();
if (&rcu_preempt_ctrlblk.rcb.rcucblist !=
rcu_preempt_ctrlblk.rcb.donetail)
- raise_softirq(RCU_SOFTIRQ);
+ invoke_rcu_cbs();
if (rcu_preempt_gp_in_progress() &&
rcu_cpu_blocking_cur_gp() &&
rcu_preempt_running_reader())
@@ -383,7 +385,7 @@ static void rcu_preempt_check_callbacks(void)
/*
* TINY_PREEMPT_RCU has an extra callback-list tail pointer to
- * update, so this is invoked from __rcu_process_callbacks() to
+ * update, so this is invoked from rcu_process_callbacks() to
* handle that case. Of course, it is invoked for all flavors of
* RCU, but RCU callbacks can appear only on one of the lists, and
* neither ->nexttail nor ->donetail can possibly be NULL, so there
@@ -400,7 +402,7 @@ static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp)
*/
static void rcu_preempt_process_callbacks(void)
{
- __rcu_process_callbacks(&rcu_preempt_ctrlblk.rcb);
+ rcu_process_callbacks(&rcu_preempt_ctrlblk.rcb);
}
/*
@@ -599,14 +601,13 @@ static void rcu_preempt_process_callbacks(void)
#endif /* #else #ifdef CONFIG_TINY_PREEMPT_RCU */
#ifdef CONFIG_DEBUG_LOCK_ALLOC
-
#include <linux/kernel_stat.h>
/*
* During boot, we forgive RCU lockdep issues. After this function is
* invoked, we start taking RCU lockdep issues seriously.
*/
-void rcu_scheduler_starting(void)
+void __init rcu_scheduler_starting(void)
{
WARN_ON(nr_context_switches() > 0);
rcu_scheduler_active = 1;