Commit 21bb8af5 authored by Alexander Lobakin's avatar Alexander Lobakin Committed by Yury Norov
Browse files

bitops: always define asm-generic non-atomic bitops 



Move generic non-atomic bitops from the asm-generic header which
gets included only when there are no architecture-specific
alternatives, to a separate independent file to make them always
available.
Almost no actual code changes, only one comment added to
generic_test_bit() saying that it's an atomic operation itself
and thus `volatile` must always stay there with no cast-aways.

Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> # comment
Suggested-by: Marco Elver <elver@google.com> # reference to kernel-doc
Signed-off-by: default avatarAlexander Lobakin <alexandr.lobakin@intel.com>
Reviewed-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: default avatarMarco Elver <elver@google.com>
Signed-off-by: default avatarYury Norov <yury.norov@gmail.com>
parent e5a16a5c

include/asm-generic/bitops/generic-non-atomic.h

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+130 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0-only */



#ifndef __ASM_GENERIC_BITOPS_GENERIC_NON_ATOMIC_H

#define __ASM_GENERIC_BITOPS_GENERIC_NON_ATOMIC_H



#include <linux/bits.h>



#ifndef _LINUX_BITOPS_H

#error only <linux/bitops.h> can be included directly

#endif



/*

 * Generic definitions for bit operations, should not be used in regular code

 * directly.

 */



/**

 * generic___set_bit - Set a bit in memory

 * @nr: the bit to set

 * @addr: the address to start counting from

 *

 * Unlike set_bit(), this function is non-atomic and may be reordered.

 * If it's called on the same region of memory simultaneously, the effect

 * may be that only one operation succeeds.

 */

static __always_inline void

generic___set_bit(unsigned int nr, volatile unsigned long *addr)

{

	unsigned long mask = BIT_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);



	*p  |= mask;

}



static __always_inline void

generic___clear_bit(unsigned int nr, volatile unsigned long *addr)

{

	unsigned long mask = BIT_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);



	*p &= ~mask;

}



/**

 * generic___change_bit - Toggle a bit in memory

 * @nr: the bit to change

 * @addr: the address to start counting from

 *

 * Unlike change_bit(), this function is non-atomic and may be reordered.

 * If it's called on the same region of memory simultaneously, the effect

 * may be that only one operation succeeds.

 */

static __always_inline

void generic___change_bit(unsigned int nr, volatile unsigned long *addr)

{

	unsigned long mask = BIT_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);



	*p ^= mask;

}



/**

 * generic___test_and_set_bit - Set a bit and return its old value

 * @nr: Bit to set

 * @addr: Address to count from

 *

 * This operation is non-atomic and can be reordered.

 * If two examples of this operation race, one can appear to succeed

 * but actually fail.  You must protect multiple accesses with a lock.

 */

static __always_inline int

generic___test_and_set_bit(unsigned int nr, volatile unsigned long *addr)

{

	unsigned long mask = BIT_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);

	unsigned long old = *p;



	*p = old | mask;

	return (old & mask) != 0;

}



/**

 * generic___test_and_clear_bit - Clear a bit and return its old value

 * @nr: Bit to clear

 * @addr: Address to count from

 *

 * This operation is non-atomic and can be reordered.

 * If two examples of this operation race, one can appear to succeed

 * but actually fail.  You must protect multiple accesses with a lock.

 */

static __always_inline int

generic___test_and_clear_bit(unsigned int nr, volatile unsigned long *addr)

{

	unsigned long mask = BIT_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);

	unsigned long old = *p;



	*p = old & ~mask;

	return (old & mask) != 0;

}



/* WARNING: non atomic and it can be reordered! */

static __always_inline int

generic___test_and_change_bit(unsigned int nr, volatile unsigned long *addr)

{

	unsigned long mask = BIT_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);

	unsigned long old = *p;



	*p = old ^ mask;

	return (old & mask) != 0;

}



/**

 * generic_test_bit - Determine whether a bit is set

 * @nr: bit number to test

 * @addr: Address to start counting from

 */

static __always_inline int

generic_test_bit(unsigned int nr, const volatile unsigned long *addr)

{

	/*

	 * Unlike the bitops with the '__' prefix above, this one *is* atomic,

	 * so `volatile` must always stay here with no cast-aways. See

	 * `Documentation/atomic_bitops.txt` for the details.

	 */

	return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));

}



#endif /* __ASM_GENERIC_BITOPS_GENERIC_NON_ATOMIC_H */

include/asm-generic/bitops/non-atomic.h

+8 −102
Original line number Diff line number Diff line
@@ -2,121 +2,27 @@ 
#ifndef _ASM_GENERIC_BITOPS_NON_ATOMIC_H_

#define _ASM_GENERIC_BITOPS_NON_ATOMIC_H_



#include <asm/types.h>

#include <asm-generic/bitops/generic-non-atomic.h>



/**

 * arch___set_bit - Set a bit in memory

 * @nr: the bit to set

 * @addr: the address to start counting from

 *

 * Unlike set_bit(), this function is non-atomic and may be reordered.

 * If it's called on the same region of memory simultaneously, the effect

 * may be that only one operation succeeds.

 */

static __always_inline void

arch___set_bit(unsigned int nr, volatile unsigned long *addr)

{

	unsigned long mask = BIT_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);



	*p  |= mask;

}

#define arch___set_bit generic___set_bit

#define __set_bit arch___set_bit



static __always_inline void

arch___clear_bit(unsigned int nr, volatile unsigned long *addr)

{

	unsigned long mask = BIT_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);



	*p &= ~mask;

}

#define arch___clear_bit generic___clear_bit

#define __clear_bit arch___clear_bit



/**

 * arch___change_bit - Toggle a bit in memory

 * @nr: the bit to change

 * @addr: the address to start counting from

 *

 * Unlike change_bit(), this function is non-atomic and may be reordered.

 * If it's called on the same region of memory simultaneously, the effect

 * may be that only one operation succeeds.

 */

static __always_inline

void arch___change_bit(unsigned int nr, volatile unsigned long *addr)

{

	unsigned long mask = BIT_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);



	*p ^= mask;

}

#define arch___change_bit generic___change_bit

#define __change_bit arch___change_bit



/**

 * arch___test_and_set_bit - Set a bit and return its old value

 * @nr: Bit to set

 * @addr: Address to count from

 *

 * This operation is non-atomic and can be reordered.

 * If two examples of this operation race, one can appear to succeed

 * but actually fail.  You must protect multiple accesses with a lock.

 */

static __always_inline int

arch___test_and_set_bit(unsigned int nr, volatile unsigned long *addr)

{

	unsigned long mask = BIT_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);

	unsigned long old = *p;



	*p = old | mask;

	return (old & mask) != 0;

}

#define arch___test_and_set_bit generic___test_and_set_bit

#define __test_and_set_bit arch___test_and_set_bit



/**

 * arch___test_and_clear_bit - Clear a bit and return its old value

 * @nr: Bit to clear

 * @addr: Address to count from

 *

 * This operation is non-atomic and can be reordered.

 * If two examples of this operation race, one can appear to succeed

 * but actually fail.  You must protect multiple accesses with a lock.

 */

static __always_inline int

arch___test_and_clear_bit(unsigned int nr, volatile unsigned long *addr)

{

	unsigned long mask = BIT_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);

	unsigned long old = *p;



	*p = old & ~mask;

	return (old & mask) != 0;

}

#define arch___test_and_clear_bit generic___test_and_clear_bit

#define __test_and_clear_bit arch___test_and_clear_bit



/* WARNING: non atomic and it can be reordered! */

static __always_inline int

arch___test_and_change_bit(unsigned int nr, volatile unsigned long *addr)

{

	unsigned long mask = BIT_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);

	unsigned long old = *p;



	*p = old ^ mask;

	return (old & mask) != 0;

}

#define arch___test_and_change_bit generic___test_and_change_bit

#define __test_and_change_bit arch___test_and_change_bit



/**

 * arch_test_bit - Determine whether a bit is set

 * @nr: bit number to test

 * @addr: Address to start counting from

 */

static __always_inline int

arch_test_bit(unsigned int nr, const volatile unsigned long *addr)

{

	return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));

}

#define arch_test_bit generic_test_bit

#define test_bit arch_test_bit



#endif /* _ASM_GENERIC_BITOPS_NON_ATOMIC_H_ */