[PATCH] bitops: generic sched_find_first_bit()

This patch introduces the C-language equivalent of the function: int
sched_find_first_bit(const unsigned long *b);

In include/asm-generic/bitops/sched.h

This code largely copied from: include/asm-powerpc/bitops.h

Signed-off-by: Akinobu Mita <mita@miraclelinux.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 36 insertions, 0 deletions

diff --git a/include/asm-generic/bitops/sched.h b/include/asm-generic/bitops/sched.h
new file mode 100644
index 000000000000..5ef93a4d009f
--- /dev/null
+++ b/include/asm-generic/bitops/sched.h
@@ -0,0 +1,36 @@
+#ifndef _ASM_GENERIC_BITOPS_SCHED_H_
+#define _ASM_GENERIC_BITOPS_SCHED_H_
+
+#include <linux/compiler.h>     /* unlikely() */
+#include <asm/types.h>
+
+/*
+ * Every architecture must define this function. It's the fastest
+ * way of searching a 140-bit bitmap where the first 100 bits are
+ * unlikely to be set. It's guaranteed that at least one of the 140
+ * bits is cleared.
+ */
+static inline int sched_find_first_bit(const unsigned long *b)
+{
+#if BITS_PER_LONG == 64
+        if (unlikely(b[0]))
+                return __ffs(b[0]);
+        if (unlikely(b[1]))
+                return __ffs(b[1]) + 64;
+        return __ffs(b[2]) + 128;
+#elif BITS_PER_LONG == 32
+        if (unlikely(b[0]))
+                return __ffs(b[0]);
+        if (unlikely(b[1]))
+                return __ffs(b[1]) + 32;
+        if (unlikely(b[2]))
+                return __ffs(b[2]) + 64;
+        if (b[3])
+                return __ffs(b[3]) + 96;
+        return __ffs(b[4]) + 128;
+#else
+#error BITS_PER_LONG not defined
+#endif
+}
+
+#endif /* _ASM_GENERIC_BITOPS_SCHED_H_ */