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bitops: always define asm-generic non-atomic bitops

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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: Alexander Lobakin <alexandr.lobakin@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Marco Elver <elver@google.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
This commit is contained in:
Alexander Lobakin 2022-06-24 14:13:06 +02:00 • committed by Yury Norov
parent e5a16a5c46
commit 21bb8af513
2 changed files with 138 additions and 102 deletions
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130
include/asm-generic/bitops/generic-non-atomic.h Normal file
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@ -0,0 +1,130 @@
/* 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 */

110
include/asm-generic/bitops/non-atomic.h
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@ -2,121 +2,27 @@
#ifndef _ASM_GENERIC_BITOPS_NON_ATOMIC_H_ #ifndef _ASM_GENERIC_BITOPS_NON_ATOMIC_H_
#define _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>
/** #define arch___set_bit generic___set_bit
* 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 __set_bit arch___set_bit #define __set_bit arch___set_bit
static __always_inline void #define arch___clear_bit generic___clear_bit
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 __clear_bit arch___clear_bit #define __clear_bit arch___clear_bit
/** #define arch___change_bit generic___change_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 __change_bit arch___change_bit #define __change_bit arch___change_bit
/** #define arch___test_and_set_bit generic___test_and_set_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 __test_and_set_bit arch___test_and_set_bit #define __test_and_set_bit arch___test_and_set_bit
/** #define arch___test_and_clear_bit generic___test_and_clear_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 __test_and_clear_bit arch___test_and_clear_bit #define __test_and_clear_bit arch___test_and_clear_bit
/* WARNING: non atomic and it can be reordered! */ #define arch___test_and_change_bit generic___test_and_change_bit
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 __test_and_change_bit arch___test_and_change_bit #define __test_and_change_bit arch___test_and_change_bit
/** #define arch_test_bit generic_test_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 test_bit arch_test_bit #define test_bit arch_test_bit
#endif /* _ASM_GENERIC_BITOPS_NON_ATOMIC_H_ */ #endif /* _ASM_GENERIC_BITOPS_NON_ATOMIC_H_ */