sh: Fix up the SH-4A mutex fastpath semantics.

This fixes up the __mutex_fastpath_xxx() routines to match the semantics
noted in the comment. Previously these were looping rather than doing a
single-pass, which is counter-intuitive, as the slow path takes care of
the looping for us in the event of contention.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

diff --git a/arch/sh/include/asm/mutex-llsc.h b/arch/sh/include/asm/mutex-llsc.h
index 7c75af5..a91990c 100644 (file)
--- a/arch/sh/include/asm/mutex-llsc.h
+++ b/arch/sh/include/asm/mutex-llsc.h
@@ -21,16 +21,18 @@
 static inline void
 __mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
 {
-       int __res;
+       int __ex_flag, __res;
 
        __asm__ __volatile__ (
-               "movli.l        @%1, %0 \n"
-               "dt             %0      \n"
-               "movco.l        %0, @%1 \n"
-               : "=&z" (__res)
+               "movli.l        @%2, %0 \n"
+               "add            #-1, %0 \n"
+               "movco.l        %0, @%2 \n"
+               "movt           %1      \n"
+               : "=&z" (__res), "=&r" (__ex_flag)
                : "r" (&(count)->counter)
                : "t");
 
+       __res |= !__ex_flag;
        if (unlikely(__res != 0))
                fail_fn(count);
 }
@@ -38,16 +40,18 @@ __mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
 static inline int
 __mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *))
 {
-       int __res;
+       int __ex_flag, __res;
 
        __asm__ __volatile__ (
-               "movli.l        @%1, %0 \n"
-               "dt             %0      \n"
-               "movco.l        %0, @%1 \n"
-               : "=&z" (__res)
+               "movli.l        @%2, %0 \n"
+               "add            #-1, %0 \n"
+               "movco.l        %0, @%2 \n"
+               "movt           %1      \n"
+               : "=&z" (__res), "=&r" (__ex_flag)
                : "r" (&(count)->counter)
                : "t");
 
+       __res |= !__ex_flag;
        if (unlikely(__res != 0))
                __res = fail_fn(count);
 
@@ -57,18 +61,19 @@ __mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *))
 static inline void
 __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
 {
-       int __res;
+       int __ex_flag, __res;
 
        __asm__ __volatile__ (
-               "1: movli.l     @%1, %0 \n\t"
+               "movli.l        @%2, %0 \n\t"
                "add            #1, %0  \n\t"
-               "movco.l        %0, @%1 \n\t"
-               "bf             1b\n\t"
-               : "=&z" (__res)
+               "movco.l        %0, @%2 \n\t"
+               "movt           %1      \n\t"
+               : "=&z" (__res), "=&r" (__ex_flag)
                : "r" (&(count)->counter)
                : "t");
 
-       if (unlikely(__res <= 0))
+       __res |= !__ex_flag;
+       if (unlikely(__res != 0))
                fail_fn(count);
 }