[PATCH] files: rcuref APIs
Adds a set of primitives to do reference counting for objects that are looked
up without locks using RCU.
Signed-off-by: Ravikiran Thirumalai <kiran_th@gmail.com>
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index f436993..bef3b69 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -45,6 +45,7 @@
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/rcupdate.h>
+#include <linux/rcuref.h>
#include <linux/cpu.h>
/* Definition for rcupdate control block. */
@@ -72,6 +73,19 @@
static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL};
static int maxbatch = 10;
+#ifndef __HAVE_ARCH_CMPXCHG
+/*
+ * We use an array of spinlocks for the rcurefs -- similar to ones in sparc
+ * 32 bit atomic_t implementations, and a hash function similar to that
+ * for our refcounting needs.
+ * Can't help multiprocessors which donot have cmpxchg :(
+ */
+
+spinlock_t __rcuref_hash[RCUREF_HASH_SIZE] = {
+ [0 ... (RCUREF_HASH_SIZE-1)] = SPIN_LOCK_UNLOCKED
+};
+#endif
+
/**
* call_rcu - Queue an RCU callback for invocation after a grace period.
* @head: structure to be used for queueing the RCU updates.