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Commit 77b9bd9c authored by Alexander van Heukelum's avatar Alexander van Heukelum Committed by Ingo Molnar
Browse files

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: default avatarAlexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent d57594c2

arch/x86/Kconfig

+3 −0
Original line number Diff line number Diff line
@@ -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

include/asm-x86/bitops_32.h

+2 −0
Original line number Diff line number Diff line
@@ -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__

include/linux/bitops.h

+34 −0
Original line number Diff line number Diff line
@@ -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);

lib/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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

lib/find_next_bit.c

+58 −0
Original line number Diff line number Diff line
@@ -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 @@ unsigned long __find_next_zero_bit(const unsigned long *addr, 
	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