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authorAkinobu Mita <mita@miraclelinux.com>2006-03-26 01:39:12 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-26 08:57:11 -0800
commit6d29ea23da033f46ac4ab359d46650a7f7474611 (patch)
tree20403ba836b8e5e7ace71cae914bbc16d552a4bd
parentc7f612cdf091def01454e7e132c7d7a3f419fbc4 (diff)
downloadop-kernel-dev-6d29ea23da033f46ac4ab359d46650a7f7474611.zip
op-kernel-dev-6d29ea23da033f46ac4ab359d46650a7f7474611.tar.gz
[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>
-rw-r--r--include/asm-generic/bitops/sched.h36
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 0000000..5ef93a4
--- /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_ */
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