rcu: move TINY_RCU from softirq to kthread
If RCU priority boosting is to be meaningful, callback invocation must
be boosted in addition to preempted RCU readers. Otherwise, in presence
of CPU real-time threads, the grace period ends, but the callbacks don't
get invoked. If the callbacks don't get invoked, the associated memory
doesn't get freed, so the system is still subject to OOM.
But it is not reasonable to priority-boost RCU_SOFTIRQ, so this commit
moves the callback invocations to a kthread, which can be boosted easily.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 03cda7b..7142ee3 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -118,7 +118,6 @@
#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 13877cb..ea025a6 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 @@
}
#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 95518e6..c0e9683 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);