x86/cmpxchg: add a locked add() helper
Mostly to remove some conditional code in spinlock.h.
Signed-off-by: Jeremy Fitzhardinge <jeremy@goop.org>
diff --git a/arch/x86/include/asm/cmpxchg.h b/arch/x86/include/asm/cmpxchg.h
index 5d3acdf..49eade1 100644
--- a/arch/x86/include/asm/cmpxchg.h
+++ b/arch/x86/include/asm/cmpxchg.h
@@ -14,6 +14,8 @@
__compiletime_error("Bad argument size for cmpxchg");
extern void __xadd_wrong_size(void)
__compiletime_error("Bad argument size for xadd");
+extern void __add_wrong_size(void)
+ __compiletime_error("Bad argument size for add");
/*
* Constants for operation sizes. On 32-bit, the 64-bit size it set to
@@ -207,4 +209,44 @@
#define xadd_sync(ptr, inc) __xadd((ptr), (inc), "lock; ")
#define xadd_local(ptr, inc) __xadd((ptr), (inc), "")
+#define __add(ptr, inc, lock) \
+ ({ \
+ __typeof__ (*(ptr)) __ret = (inc); \
+ switch (sizeof(*(ptr))) { \
+ case __X86_CASE_B: \
+ asm volatile (lock "addb %b1, %0\n" \
+ : "+m" (*(ptr)) : "ri" (inc) \
+ : "memory", "cc"); \
+ break; \
+ case __X86_CASE_W: \
+ asm volatile (lock "addw %w1, %0\n" \
+ : "+m" (*(ptr)) : "ri" (inc) \
+ : "memory", "cc"); \
+ break; \
+ case __X86_CASE_L: \
+ asm volatile (lock "addl %1, %0\n" \
+ : "+m" (*(ptr)) : "ri" (inc) \
+ : "memory", "cc"); \
+ break; \
+ case __X86_CASE_Q: \
+ asm volatile (lock "addq %1, %0\n" \
+ : "+m" (*(ptr)) : "ri" (inc) \
+ : "memory", "cc"); \
+ break; \
+ default: \
+ __add_wrong_size(); \
+ } \
+ __ret; \
+ })
+
+/*
+ * add_*() adds "inc" to "*ptr"
+ *
+ * __add() takes a lock prefix
+ * add_smp() is locked when multiple CPUs are online
+ * add_sync() is always locked
+ */
+#define add_smp(ptr, inc) __add((ptr), (inc), LOCK_PREFIX)
+#define add_sync(ptr, inc) __add((ptr), (inc), "lock; ")
+
#endif /* ASM_X86_CMPXCHG_H */