add the x86_64 version of mutex.h, optimized in assembly.
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Arjan van de Ven <[email protected]>
----
include/asm-x86_64/mutex.h | 97 +++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 97 insertions(+)
Index: linux/include/asm-x86_64/mutex.h
===================================================================
--- /dev/null
+++ linux/include/asm-x86_64/mutex.h
@@ -0,0 +1,97 @@
+/*
+ * Assembly implementation of the mutex fastpath, based on atomic
+ * decrement/increment.
+ *
+ * started by Ingo Molnar:
+ *
+ * Copyright (C) 2004, 2005 Red Hat, Inc., Ingo Molnar <[email protected]>
+ */
+#ifndef _ASM_MUTEX_H
+#define _ASM_MUTEX_H
+
+/**
+ * __mutex_fastpath_lock - 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 <fn> if the result is negative.
+ */
+#define __mutex_fastpath_lock(v, fn_name) \
+do { \
+ /* type-check the function too: */ \
+ fastcall void (*__tmp)(atomic_t *) = fn_name; \
+ unsigned long dummy; \
+ \
+ (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" \
+ " jmp 1b \n" \
+ LOCK_SECTION_END \
+ \
+ :"=D" (dummy) \
+ : "D" (v) \
+ : "rax", "rsi", "rdx", "rcx", \
+ "r8", "r9", "r10", "r11", "memory"); \
+} while (0)
+
+/**
+ * __mutex_fastpath_unlock - 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 <fn> if the result is nonpositive.
+ */
+#define __mutex_fastpath_unlock(v, fn_name) \
+do { \
+ /* type-check the function too: */ \
+ fastcall void (*__tmp)(atomic_t *) = fn_name; \
+ unsigned long dummy; \
+ \
+ (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" \
+ " jmp 1b \n" \
+ LOCK_SECTION_END \
+ \
+ :"=D" (dummy) \
+ : "D" (v) \
+ : "rax", "rsi", "rdx", "rcx", \
+ "r8", "r9", "r10", "r11", "memory"); \
+} while (0)
+
+#define __mutex_slowpath_needs_to_unlock() 1
+
+/**
+ * __mutex_fastpath_trylock - try to acquire the mutex, without waiting
+ *
+ * @count: pointer of type atomic_t
+ * @fn: fallback function
+ *
+ * Change the count from 1 to 0 and return 1 (success), or return 0 (failure)
+ * if it wasn't 1 originally. [the fallback function is never used on
+ * x86_64, because all x86_64 CPUs have a CMPXCHG instruction.]
+ */
+static inline int
+__mutex_fastpath_trylock(atomic_t *count, int (*fn)(atomic_t *))
+{
+ if (likely(atomic_cmpxchg(count, 1, 0)) == 1)
+ return 1;
+ else
+ return 0;
+}
+
+#endif
-
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