[patch 3/8] mutex subsystem, add atomic_*_call_if_*() to i386

[Ingo Molnar <mingo@elte.hu>]

add two new atomic ops to i386: atomic_dec_call_if_negative() and
atomic_inc_call_if_nonpositive(), which are conditional-call-if
atomic operations. Needed by the new mutex code.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

----

 include/asm-i386/atomic.h |   55 ++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 55 insertions(+)

Index: linux/include/asm-i386/atomic.h
===================================================================
--- linux.orig/include/asm-i386/atomic.h
+++ linux/include/asm-i386/atomic.h
@@ -240,6 +240,61 @@ static __inline__ int atomic_sub_return(
 #define atomic_inc_return(v)  (atomic_add_return(1,v))
 #define atomic_dec_return(v)  (atomic_sub_return(1,v))
 
+/**
+ * atomic_dec_call_if_negative - decrement and call function if negative
+ * @v: pointer of type atomic_t
+ * @fn: function to call if the result is negative
+ *
+ * Atomically decrements @v and calls a function if the result is negative.
+ */
+#define atomic_dec_call_if_negative(v, fn_name)				\
+do {									\
+	fastcall void (*__tmp)(atomic_t *) = fn_name;			\
+									\
+	(void)__tmp;							\
+	typecheck(atomic_t *, v);					\
+									\
+	__asm__ __volatile__(						\
+		LOCK "decl (%%eax)\n"  					\
+		"js 2f\n"						\
+		"1:\n"							\
+		LOCK_SECTION_START("")					\
+		"2: call "#fn_name"\n\t"				\
+		"jmp 1b\n"						\
+		LOCK_SECTION_END					\
+		:							\
+		:"a" (v)						\
+		:"memory","cx","dx");					\
+} while (0)
+
+/**
+ * atomic_inc_call_if_nonpositive - increment and call function if nonpositive
+ * @v: pointer of type atomic_t
+ * @fn: function to call if the result is nonpositive
+ *
+ * Atomically increments @v and calls a function if the result is nonpositive.
+ */
+#define atomic_inc_call_if_nonpositive(v, fn_name)			\
+do {									\
+	fastcall void (*__tmp)(atomic_t *) = fn_name;			\
+									\
+	(void)__tmp;							\
+	typecheck(atomic_t *, v);					\
+									\
+	__asm__ __volatile__(						\
+		LOCK "incl (%%eax)\n"  					\
+		"jle 2f\n"						\
+		"1:\n"							\
+		LOCK_SECTION_START("")					\
+		"2: call "#fn_name"\n\t"				\
+		"jmp 1b\n"						\
+		LOCK_SECTION_END					\
+		:							\
+		:"a" (v)						\
+		:"memory","cx","dx");					\
+} while (0)
+
+
 /* These are x86-specific, used by some header files */
 #define atomic_clear_mask(mask, addr) \
 __asm__ __volatile__(LOCK "andl %0,%1" \