x86: generic versions of find_first_(zero_)bit, convert i386

Generic versions of __find_first_bit and __find_first_zero_bit
are introduced as simplified versions of __find_next_bit and
__find_next_zero_bit. Their compilation and use are guarded by
a new config variable GENERIC_FIND_FIRST_BIT.

The generic versions of find_first_bit and find_first_zero_bit
are implemented in terms of the newly introduced __find_first_bit
and __find_first_zero_bit.

This patch does not remove the i386-specific implementation,
but it does switch i386 to use the generic functions by setting
GENERIC_FIND_FIRST_BIT=y for X86_32.

Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5639de47ed454350cb24172269f530fbfa96a7e8..1a69b68ff6cc6b1bec389523bb47bf924a776245 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -77,6 +77,9 @@ config GENERIC_BUG
        def_bool y
        depends on BUG
 
+config GENERIC_FIND_FIRST_BIT
+       def_bool X86_32
+
 config GENERIC_FIND_NEXT_BIT
        def_bool y
 

diff --git a/include/asm-x86/bitops_32.h b/include/asm-x86/bitops_32.h
index 3ed64b21b765d116a563e042b3bd6d1a71f70c81..ba2c0defafa8c7d3ec8f0adb53b508be660334e0 100644 (file)
--- a/include/asm-x86/bitops_32.h
+++ b/include/asm-x86/bitops_32.h
@@ -5,6 +5,7 @@
  * Copyright 1992, Linus Torvalds.
  */
 
+#ifndef CONFIG_GENERIC_FIND_FIRST_BIT
 /**
  * find_first_zero_bit - find the first zero bit in a memory region
  * @addr: The address to start the search at
@@ -59,6 +60,7 @@ static inline unsigned find_first_bit(const unsigned long *addr, unsigned size)
        }
        return x;
 }
+#endif
 
 #ifdef __KERNEL__
 

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 3865f2c93bd8282e02bee4880d382a7448703d16..355d67ba3bdc66de8c190e1eb87180bfedf419f3 100644 (file)
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -113,6 +113,40 @@ static inline unsigned fls_long(unsigned long l)
 }
 
 #ifdef __KERNEL__
+#ifdef CONFIG_GENERIC_FIND_FIRST_BIT
+extern unsigned long __find_first_bit(const unsigned long *addr,
+               unsigned long size);
+
+/**
+ * find_first_bit - find the first set bit in a memory region
+ * @addr: The address to start the search at
+ * @size: The maximum size to search
+ *
+ * Returns the bit number of the first set bit.
+ */
+static __always_inline unsigned long
+find_first_bit(const unsigned long *addr, unsigned long size)
+{
+       return __find_first_bit(addr, size);
+}
+
+extern unsigned long __find_first_zero_bit(const unsigned long *addr,
+               unsigned long size);
+
+/**
+ * find_first_zero_bit - find the first cleared bit in a memory region
+ * @addr: The address to start the search at
+ * @size: The maximum size to search
+ *
+ * Returns the bit number of the first cleared bit.
+ */
+static __always_inline unsigned long
+find_first_zero_bit(const unsigned long *addr, unsigned long size)
+{
+       return __find_first_zero_bit(addr, size);
+}
+#endif /* CONFIG_GENERIC_FIND_FIRST_BIT */
+
 #ifdef CONFIG_GENERIC_FIND_NEXT_BIT
 extern unsigned long __find_next_bit(const unsigned long *addr,
                unsigned long size, unsigned long offset);

diff --git a/lib/Makefile b/lib/Makefile
index bf8000fc7d48e771eb560f10fde894c64bffbb63..2d7001b7f5a4d641be0c618a6405d4c9863b41fb 100644 (file)
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -29,6 +29,7 @@ obj-$(CONFIG_DEBUG_LOCKING_API_SELFTESTS) += locking-selftest.o
 obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock_debug.o
 lib-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
 lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
+lib-$(CONFIG_GENERIC_FIND_FIRST_BIT) += find_next_bit.o
 lib-$(CONFIG_GENERIC_FIND_NEXT_BIT) += find_next_bit.o
 obj-$(CONFIG_GENERIC_HWEIGHT) += hweight.o
 obj-$(CONFIG_LOCK_KERNEL) += kernel_lock.o

diff --git a/lib/find_next_bit.c b/lib/find_next_bit.c
index ce94c4c92d10c0ec3720528811a48ac7508bd8fd..d3f5784807b45a00fa2301727951f6fb3e325f35 100644 (file)
--- a/lib/find_next_bit.c
+++ b/lib/find_next_bit.c
@@ -16,6 +16,7 @@
 
 #define BITOP_WORD(nr)         ((nr) / BITS_PER_LONG)
 
+#ifdef CONFIG_GENERIC_FIND_NEXT_BIT
 /*
  * Find the next set bit in a memory region.
  */
@@ -102,6 +103,63 @@ found_middle:
        return result + ffz(tmp);
 }
 EXPORT_SYMBOL(__find_next_zero_bit);
+#endif /* CONFIG_GENERIC_FIND_NEXT_BIT */
+
+#ifdef CONFIG_GENERIC_FIND_FIRST_BIT
+/*
+ * Find the first set bit in a memory region.
+ */
+unsigned long __find_first_bit(const unsigned long *addr,
+               unsigned long size)
+{
+       const unsigned long *p = addr;
+       unsigned long result = 0;
+       unsigned long tmp;
+
+       while (size & ~(BITS_PER_LONG-1)) {
+               if ((tmp = *(p++)))
+                       goto found;
+               result += BITS_PER_LONG;
+               size -= BITS_PER_LONG;
+       }
+       if (!size)
+               return result;
+
+       tmp = (*p) & (~0UL >> (BITS_PER_LONG - size));
+       if (tmp == 0UL)         /* Are any bits set? */
+               return result + size;   /* Nope. */
+found:
+       return result + __ffs(tmp);
+}
+EXPORT_SYMBOL(__find_first_bit);
+
+/*
+ * Find the first cleared bit in a memory region.
+ */
+unsigned long __find_first_zero_bit(const unsigned long *addr,
+               unsigned long size)
+{
+       const unsigned long *p = addr;
+       unsigned long result = 0;
+       unsigned long tmp;
+
+       while (size & ~(BITS_PER_LONG-1)) {
+               if (~(tmp = *(p++)))
+                       goto found;
+               result += BITS_PER_LONG;
+               size -= BITS_PER_LONG;
+       }
+       if (!size)
+               return result;
+
+       tmp = (*p) | (~0UL << size);
+       if (tmp == ~0UL)        /* Are any bits zero? */
+               return result + size;   /* Nope. */
+found:
+       return result + ffz(tmp);
+}
+EXPORT_SYMBOL(__find_first_zero_bit);
+#endif /* CONFIG_GENERIC_FIND_FIRST_BIT */
 
 #ifdef __BIG_ENDIAN