lkml.org 
[lkml]   [2006]   [Jan]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
Subject[PATCH 6/12] generic sched_find_first_bit()
From
This patch introduces the C-language equivalent of the function:
int sched_find_first_bit(const unsigned long *b);

HAVE_ARCH_SCHED_BITOPS is defined when the architecture has its own
version of these functions.

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

Index: 2.6-git/include/asm-generic/bitops.h
===================================================================
--- 2.6-git.orig/include/asm-generic/bitops.h 2006-01-25 19:14:10.000000000 +0900
+++ 2.6-git/include/asm-generic/bitops.h 2006-01-25 19:14:10.000000000 +0900
@@ -383,6 +383,41 @@

#ifdef __KERNEL__

+#ifndef HAVE_ARCH_SCHED_BITOPS
+
+#include <linux/compiler.h> /* unlikely() */
+
+/*
+ * 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 /* HAVE_ARCH_SCHED_BITOPS */
+
/*
* ffs: find first bit set. This is defined the same way as
* the libc and compiler builtin ffs routines, therefore
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
\
 
 \ /
  Last update: 2006-01-26 04:36    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site