[patch 04/15] Generic Mutex Subsystem, add-atomic-call-func-x86_64.patch

[Ingo Molnar]

add two new atomic ops to x86_64: 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@xxxxxxx>

----

 include/asm-x86_64/atomic.h |   56 ++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 56 insertions(+)

Index: linux/include/asm-x86_64/atomic.h
===================================================================
--- linux.orig/include/asm-x86_64/atomic.h
+++ linux/include/asm-x86_64/atomic.h
@@ -203,6 +203,62 @@ 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.
+ * NOTE: the function is type-checked and must be a fastcall.
+ */
+#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 (%%rdi)\n"  					\
+		"js 2f\n"						\
+		"1:\n"							\
+		LOCK_SECTION_START("")					\
+		"2: call "#fn_name"\n\t"				\
+		"jmp 1b\n"						\
+		LOCK_SECTION_END					\
+		:							\
+		:"D" (v)						\
+		:"memory");						\
+} 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.
+ * NOTE: the function is type-checked and must be a fastcall.
+ */
+#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 (%%rdi)\n"  					\
+		"jle 2f\n"						\
+		"1:\n"							\
+		LOCK_SECTION_START("")					\
+		"2: call "#fn_name"\n\t"				\
+		"jmp 1b\n"						\
+		LOCK_SECTION_END					\
+		:							\
+		:"D" (v)						\
+		:"memory");						\
+} while (0)
+
 /* An 64bit atomic type */
 
 typedef struct { volatile long counter; } atomic64_t;
-
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