Ingo Molnar wrote:
From: Arjan van de Ven <[email protected]>
add the i386 version of mutex.h, optimized in assembly.
+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)
+ return 1;
+ return 0;
+#else
+ return fail_fn(count);
+#endif
+}
asm-i386 version I think really should just use atomic_cmpxchg unconditionally,
because otherwise an i386 compatible kernel will not use cmpxchg even when
running on 486+ (not sure how important that is these days, but still...).
--
SUSE Labs, Novell Inc.
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