aboutsummaryrefslogtreecommitdiff
path: root/arch/blackfin/include/asm/mutex-dec.h
diff options
context:
space:
mode:
authorGraf Yang <graf.yang@analog.com>2009-01-07 23:14:39 +0800
committerBryan Wu <cooloney@kernel.org>2009-01-07 23:14:39 +0800
commit6b3087c64a92a36ae20d33479b4df6d7afc910d4 (patch)
tree95984fc623658ebf150d0d912a7f6c5a0301a5a9 /arch/blackfin/include/asm/mutex-dec.h
parentc51b4488cd5bff08ed5690a8f303ff7f0894da2a (diff)
Blackfin arch: SMP supporting patchset: Blackfin header files and machine common code
Blackfin dual core BF561 processor can support SMP like features. https://docs.blackfin.uclinux.org/doku.php?id=linux-kernel:smp-like In this patch, we provide SMP extend to Blackfin header files and machine common code Signed-off-by: Graf Yang <graf.yang@analog.com> Signed-off-by: Bryan Wu <cooloney@kernel.org>
Diffstat (limited to 'arch/blackfin/include/asm/mutex-dec.h')
-rw-r--r--arch/blackfin/include/asm/mutex-dec.h112
1 files changed, 112 insertions, 0 deletions
diff --git a/arch/blackfin/include/asm/mutex-dec.h b/arch/blackfin/include/asm/mutex-dec.h
new file mode 100644
index 00000000000..0134151656a
--- /dev/null
+++ b/arch/blackfin/include/asm/mutex-dec.h
@@ -0,0 +1,112 @@
+/*
+ * include/asm-generic/mutex-dec.h
+ *
+ * Generic implementation of the mutex fastpath, based on atomic
+ * decrement/increment.
+ */
+#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
+ * @fail_fn: function to call if the original value was not 1
+ *
+ * Change the count from 1 to a value lower than 1, and call <fail_fn> if
+ * it wasn't 1 originally. This function MUST leave the value lower than
+ * 1 even when the "1" assertion wasn't true.
+ */
+static inline void
+__mutex_fastpath_lock(atomic_t *count, fastcall void (*fail_fn)(atomic_t *))
+{
+ if (unlikely(atomic_dec_return(count) < 0))
+ fail_fn(count);
+ else
+ smp_mb();
+}
+
+/**
+ * __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
+ * @fail_fn: function to call if the original value was not 1
+ *
+ * Change the count from 1 to a value lower than 1, and call <fail_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, fastcall int (*fail_fn)(atomic_t *))
+{
+ if (unlikely(atomic_dec_return(count) < 0))
+ return fail_fn(count);
+ else {
+ smp_mb();
+ return 0;
+ }
+}
+
+/**
+ * __mutex_fastpath_unlock - try to promote the count from 0 to 1
+ * @count: pointer of type atomic_t
+ * @fail_fn: function to call if the original value was not 0
+ *
+ * Try to promote the count from 0 to 1. If it wasn't 0, call <fail_fn>.
+ * In the failure case, this function is allowed to either set the value to
+ * 1, or to set it to a value lower than 1.
+ *
+ * If the implementation sets it to a value of lower than 1, then the
+ * __mutex_slowpath_needs_to_unlock() macro needs to return 1, it needs
+ * to return 0 otherwise.
+ */
+static inline void
+__mutex_fastpath_unlock(atomic_t *count, fastcall void (*fail_fn)(atomic_t *))
+{
+ smp_mb();
+ if (unlikely(atomic_inc_return(count) <= 0))
+ fail_fn(count);
+}
+
+#define __mutex_slowpath_needs_to_unlock() 1
+
+/**
+ * __mutex_fastpath_trylock - try to acquire the mutex, without waiting
+ *
+ * @count: pointer of type atomic_t
+ * @fail_fn: fallback function
+ *
+ * Change the count from 1 to a value lower than 1, and return 0 (failure)
+ * if it wasn't 1 originally, or return 1 (success) otherwise. This function
+ * MUST leave the value lower than 1 even when the "1" assertion wasn't true.
+ * Additionally, if the value was < 0 originally, this function must not leave
+ * it to 0 on failure.
+ *
+ * If the architecture has no effective trylock variant, it should call the
+ * <fail_fn> spinlock-based trylock variant unconditionally.
+ */
+static inline int
+__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
+{
+ /*
+ * We have two variants here. The cmpxchg based one is the best one
+ * because it never induce a false contention state. It is included
+ * here because architectures using the inc/dec algorithms over the
+ * xchg ones are much more likely to support cmpxchg natively.
+ *
+ * If not we fall back to the spinlock based variant - that is
+ * just as efficient (and simpler) as a 'destructive' probing of
+ * the mutex state would be.
+ */
+#ifdef __HAVE_ARCH_CMPXCHG
+ if (likely(atomic_cmpxchg(count, 1, 0) == 1)) {
+ smp_mb();
+ return 1;
+ }
+ return 0;
+#else
+ return fail_fn(count);
+#endif
+}
+
+#endif