[patch 2.4.11-pre5] atomic_dec_and_lock() for alpha

[Ivan Kokshaysky <ink@jurassic.park.msu.ru>]

Similar to x86 version, but somewhat simpler due to ll/sc.

Ivan.

--- 2.4.11p5/arch/alpha/lib/dec_and_lock.c	Thu Jan  1 00:00:00 1970
+++ linux/arch/alpha/lib/dec_and_lock.c	Fri Oct  5 17:37:20 2001
@@ -0,0 +1,35 @@
+/*
+ * arch/alpha/lib/dec_and_lock.c
+ *
+ * ll/sc version of atomic_dec_and_lock()
+ */
+
+#include <linux/spinlock.h>
+#include <asm/atomic.h>
+
+int atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
+{
+	int cnt;
+	__asm__ __volatile__(
+	"1:	ldl_l	%0,%1\n"
+	"	subl	%0,1,%0\n"
+	"	beq	%0,2f\n"
+	"	stl_c	%0,%1\n"
+	"	beq	%0,3f\n"
+	"	mb\n"
+	"	mov	$31,$0\n"
+	"	ret\n"
+	"2:\n"
+	".subsection 2\n"
+	"3:	br	1b\n"
+	".previous"
+	:"=&r" (cnt), "=m" (atomic->counter)
+	:"m" (atomic->counter) : "$0", "memory");
+
+	/* Slow path */
+	spin_lock(lock);
+	if (atomic_dec_and_test(atomic))
+		return 1;
+	spin_unlock(lock);
+	return 0;
+}
--- 2.4.11p5/arch/alpha/lib/Makefile	Wed Jun 20 22:10:27 2001
+++ linux/arch/alpha/lib/Makefile	Fri Oct  5 17:37:20 2001
@@ -49,6 +49,10 @@ OBJS =	__divqu.o __remqu.o __divlu.o __r
 	fpreg.o \
 	callback_srm.o srm_puts.o srm_printk.o
 
+ifeq ($(CONFIG_SMP),y)
+  OBJS += dec_and_lock.o
+endif
+
 lib.a: $(OBJS)
 	$(AR) rcs lib.a $(OBJS)
 
--- 2.4.11p5/arch/alpha/kernel/alpha_ksyms.c	Fri Sep 14 02:21:32 2001
+++ linux/arch/alpha/kernel/alpha_ksyms.c	Fri Oct  5 19:56:39 2001
@@ -215,6 +215,7 @@ EXPORT_SYMBOL(__global_cli);
 EXPORT_SYMBOL(__global_sti);
 EXPORT_SYMBOL(__global_save_flags);
 EXPORT_SYMBOL(__global_restore_flags);
+EXPORT_SYMBOL(atomic_dec_and_lock);
 #if DEBUG_SPINLOCK
 EXPORT_SYMBOL(spin_unlock);
 EXPORT_SYMBOL(debug_spin_lock);
--- 2.4.11p5/arch/alpha/config.in	Fri Oct  5 17:27:50 2001
+++ linux/arch/alpha/config.in	Fri Oct  5 17:37:20 2001
@@ -217,6 +217,10 @@ then
 	bool 'Symmetric multi-processing support' CONFIG_SMP
 fi
 
+if [ "$CONFIG_SMP" = "y" ]; then
+   define_bool CONFIG_HAVE_DEC_LOCK y
+fi
+
 if [ "$CONFIG_EXPERIMENTAL" = "y" ]; then
    bool 'Discontiguous Memory Support' CONFIG_DISCONTIGMEM
    if [ "$CONFIG_DISCONTIGMEM" = "y" ]; then