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Subject[PATCH/RFC] asm-generic/mutex-dec.h: add SMP support
Date
To make these guys work on SMP systems, we just need to sprinkle a few
barriers around.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
---
note: this is what the Blackfin SMP port is using, but it doesn't seem
like other SMP ports are ... so I wonder if we're just trying too hard
and these barriers aren't actually necessary ?

include/asm-generic/mutex-dec.h | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/include/asm-generic/mutex-dec.h b/include/asm-generic/mutex-dec.h
index f104af7..e746c3c 100644
--- a/include/asm-generic/mutex-dec.h
+++ b/include/asm-generic/mutex-dec.h
@@ -22,6 +22,8 @@ __mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
{
if (unlikely(atomic_dec_return(count) < 0))
fail_fn(count);
+ else
+ smp_mb();
}

/**
@@ -39,6 +41,7 @@ __mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *))
{
if (unlikely(atomic_dec_return(count) < 0))
return fail_fn(count);
+ smp_mb();
return 0;
}

@@ -58,6 +61,7 @@ __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 *))
{
+ smp_mb();
if (unlikely(atomic_inc_return(count) <= 0))
fail_fn(count);
}
@@ -82,8 +86,10 @@ __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
static inline int
__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
{
- if (likely(atomic_cmpxchg(count, 1, 0) == 1))
+ if (likely(atomic_cmpxchg(count, 1, 0) == 1)) {
+ smp_mb();
return 1;
+ }
return 0;
}

--
1.7.5.rc3


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