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
--- 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 @@
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 @@
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);
}
