add the two generic mutex fastpath implementations.
Signed-off-by: Arjan van de Ven <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
----
include/asm-generic/mutex-dec.h | 66 ++++++++++++++++++++++++++++++++++++
include/asm-generic/mutex-xchg.h | 71 +++++++++++++++++++++++++++++++++++++++
2 files changed, 137 insertions(+)
Index: linux/include/asm-generic/mutex-dec.h
===================================================================
--- /dev/null
+++ linux/include/asm-generic/mutex-dec.h
@@ -0,0 +1,66 @@
+/*
+ * asm-generic/mutex-dec.h
+ *
+ * Generic wrappers for the mutex fastpath based on an xchg() implementation
+ *
+ */
+#ifndef _ASM_GENERIC_MUTEX_DEC_H
+#define _ASM_GENERIC_MUTEX_DEC_H
+
+/**
+ * __mutex_fastpath_lock - try to take the lock by moving the count
+ * from 1 to a 0 value
+ * @count: pointer of type atomic_t
+ * @fn: function to call if the original value was not 1
+ *
+ * Change the count from 1 to a value lower than 1, and call <fn> if it
+ * wasn't 1 originally. This function MUST leave the value lower than 1
+ * even when the "1" assertion wasn't true.
+ */
+#define __mutex_fastpath_lock(count, fn_name) \
+do { \
+ if (unlikely(atomic_dec_return(count) < 0)) \
+ fn_name(count); \
+} while (0)
+
+/**
+ * __mutex_fastpath_lock_retval - try to take the lock by moving the count
+ * from 1 to a 0 value
+ * @count: pointer of type atomic_t
+ * @fn: function to call if the original value was not 1
+ *
+ * Change the count from 1 to a value lower than 1, and call <fn> if it
+ * wasn't 1 originally. This function returns 0 if the fastpath succeeds,
+ * or anything the slow path function returns
+ */
+static inline int
+__mutex_fastpath_lock_retval(atomic_t *count,
+ int (*fn_name)(atomic_t *))
+{
+ if (unlikely(atomic_dec_return(count) < 0))
+ return fn_name(count);
+ else
+ return 0;
+}
+
+/**
+ * __mutex_fastpath_unlock - try to promote the mutex from 0 to 1
+ * @count: pointer of type atomic_t
+ * @fn: function to call if the original value was not 1
+ *
+ * try to promote the mutex from 0 to 1. if it wasn't 0, call <function>
+ * In the failure case, this function is allowed to either set the value to
+ * 1, or to set it to a value lower than one.
+ * If the implementation sets it to a value of lower than one, the
+ * __mutex_slowpath_needs_to_unlock() macro needs to return 1, it needs
+ * to return 0 otherwise.
+ */
+#define __mutex_fastpath_unlock(count, fn_name) \
+do { \
+ if (unlikely(atomic_inc_return(count) <= 0)) \
+ fn_name(count); \
+} while (0)
+
+#define __mutex_slowpath_needs_to_unlock() 1
+
+#endif
Index: linux/include/asm-generic/mutex-xchg.h
===================================================================
--- /dev/null
+++ linux/include/asm-generic/mutex-xchg.h
@@ -0,0 +1,71 @@
+/*
+ * asm-generic/mutex-xchg.h
+ *
+ * Generic wrappers for the mutex fastpath based on an xchg() implementation
+ *
+ * NOTE: An xchg based implementation is less optimal than a
+ * decrement/increment based implementation. If your architecture
+ * has a reasonable atomic dec/inc then don't use this file, use
+ * mutex-dec.h instead!
+ */
+#ifndef _ASM_GENERIC_MUTEX_XCHG_H
+#define _ASM_GENERIC_MUTEX_XCHG_H
+
+/**
+ * __mutex_fastpath_lock - try to take the lock by moving the count
+ * from 1 to a 0 value
+ * @count: pointer of type atomic_t
+ * @fn: function to call if the original value was not 1
+ *
+ * Change the count from 1 to a value lower than 1, and call <fn> if it
+ * wasn't 1 originally. This function MUST leave the value lower than 1
+ * even when the "1" assertion wasn't true.
+ */
+#define __mutex_fastpath_lock(count, fn_name) \
+do { \
+ if (unlikely(atomic_xchg(count, 0) != 1)) \
+ fn_name(count); \
+} while (0)
+
+
+/**
+ * __mutex_fastpath_lock_retval - try to take the lock by moving the count
+ * from 1 to a 0 value
+ * @count: pointer of type atomic_t
+ * @fn: function to call if the original value was not 1
+ *
+ * Change the count from 1 to a value lower than 1, and call <fn> if it
+ * wasn't 1 originally. This function returns 0 if the fastpath succeeds,
+ * or anything the slow path function returns
+ */
+static inline int
+__mutex_fastpath_lock_retval(atomic_t *count,
+ int (*fn_name)(atomic_t *))
+{
+ if (unlikely(atomic_xchg(count, 0) != 1))
+ return fn_name(count);
+ else
+ return 0;
+}
+
+/**
+ * __mutex_fastpath_unlock - try to promote the mutex from 0 to 1
+ * @count: pointer of type atomic_t
+ * @fn: function to call if the original value was not 1
+ *
+ * try to promote the mutex from 0 to 1. if it wasn't 0, call <function>
+ * In the failure case, this function is allowed to either set the value to
+ * 1, or to set it to a value lower than one.
+ * If the implementation sets it to a value of lower than one, the
+ * __mutex_slowpath_needs_to_unlock() macro needs to return 1, it needs
+ * to return 0 otherwise.
+ */
+#define __mutex_fastpath_unlock(count, fn_name) \
+do { \
+ if (unlikely(atomic_xchg(count, 1) != 0)) \
+ fn_name(count); \
+} while (0)
+
+#define __mutex_slowpath_needs_to_unlock() 0
+
+#endif
-
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