srcu: Create a tiny SRCU

In response to automated complaints about modifications to SRCU
increasing its size, this commit creates a tiny SRCU that is
used in SMP=n && PREEMPT=n builds.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 8 insertions, 61 deletions

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 73a1b6296224..907f09b14eda 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -34,28 +34,7 @@
 #include <linux/workqueue.h>
 #include <linux/rcu_segcblist.h>
 
-struct srcu_array {
-	unsigned long lock_count[2];
-	unsigned long unlock_count[2];
-};
-
-struct srcu_struct {
-	unsigned long completed;
-	unsigned long srcu_gp_seq;
-	atomic_t srcu_exp_cnt;
-	struct srcu_array __percpu *per_cpu_ref;
-	spinlock_t queue_lock; /* protect ->srcu_cblist */
-	struct rcu_segcblist srcu_cblist;
-	struct delayed_work work;
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-	struct lockdep_map dep_map;
-#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
-};
-
-/* Values for -> state variable. */
-#define SRCU_STATE_IDLE		0
-#define SRCU_STATE_SCAN1	1
-#define SRCU_STATE_SCAN2	2
+struct srcu_struct;
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 
@@ -77,42 +56,13 @@ int init_srcu_struct(struct srcu_struct *sp);
 #define __SRCU_DEP_MAP_INIT(srcu_name)
 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
-void process_srcu(struct work_struct *work);
-
-#define __SRCU_STRUCT_INIT(name)					\
-	{								\
-		.completed = -300,					\
-		.per_cpu_ref = &name##_srcu_array,			\
-		.queue_lock = __SPIN_LOCK_UNLOCKED(name.queue_lock),	\
-		.srcu_cblist = RCU_SEGCBLIST_INITIALIZER(name.srcu_cblist),\
-		.work = __DELAYED_WORK_INITIALIZER(name.work, process_srcu, 0),\
-		__SRCU_DEP_MAP_INIT(name)				\
-	}
-
-/*
- * Define and initialize a srcu struct at build time.
- * Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it.
- *
- * Note that although DEFINE_STATIC_SRCU() hides the name from other
- * files, the per-CPU variable rules nevertheless require that the
- * chosen name be globally unique.  These rules also prohibit use of
- * DEFINE_STATIC_SRCU() within a function.  If these rules are too
- * restrictive, declare the srcu_struct manually.  For example, in
- * each file:
- *
- *	static struct srcu_struct my_srcu;
- *
- * Then, before the first use of each my_srcu, manually initialize it:
- *
- *	init_srcu_struct(&my_srcu);
- *
- * See include/linux/percpu-defs.h for the rules on per-CPU variables.
- */
-#define __DEFINE_SRCU(name, is_static)					\
-	static DEFINE_PER_CPU(struct srcu_array, name##_srcu_array);\
-	is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name)
-#define DEFINE_SRCU(name)		__DEFINE_SRCU(name, /* not static */)
-#define DEFINE_STATIC_SRCU(name)	__DEFINE_SRCU(name, static)
+#ifdef CONFIG_TINY_SRCU
+#include <linux/srcutiny.h>
+#elif defined(CONFIG_TREE_SRCU)
+#include <linux/srcutree.h>
+#else
+#error "Unknown SRCU implementation specified to kernel configuration"
+#endif
 
 /**
  * call_srcu() - Queue a callback for invocation after an SRCU grace period
@@ -138,9 +88,6 @@ void cleanup_srcu_struct(struct srcu_struct *sp);
 int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
 void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
 void synchronize_srcu(struct srcu_struct *sp);
-void synchronize_srcu_expedited(struct srcu_struct *sp);
-unsigned long srcu_batches_completed(struct srcu_struct *sp);
-void srcu_barrier(struct srcu_struct *sp);
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC