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https://gitee.com/bianbu-linux/linux-6.6
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21bb8af513
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>
130 lines
3.6 KiB
C
130 lines
3.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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#ifndef __ASM_GENERIC_BITOPS_GENERIC_NON_ATOMIC_H
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#define __ASM_GENERIC_BITOPS_GENERIC_NON_ATOMIC_H
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#include <linux/bits.h>
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#ifndef _LINUX_BITOPS_H
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#error only <linux/bitops.h> can be included directly
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#endif
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/*
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* Generic definitions for bit operations, should not be used in regular code
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* directly.
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*/
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/**
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* generic___set_bit - Set a bit in memory
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* @nr: the bit to set
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* @addr: the address to start counting from
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*
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* Unlike set_bit(), this function is non-atomic and may be reordered.
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* If it's called on the same region of memory simultaneously, the effect
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* may be that only one operation succeeds.
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*/
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static __always_inline void
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generic___set_bit(unsigned int nr, volatile unsigned long *addr)
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{
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unsigned long mask = BIT_MASK(nr);
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unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
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*p |= mask;
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}
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static __always_inline void
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generic___clear_bit(unsigned int nr, volatile unsigned long *addr)
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{
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unsigned long mask = BIT_MASK(nr);
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unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
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*p &= ~mask;
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}
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/**
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* generic___change_bit - Toggle a bit in memory
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* @nr: the bit to change
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* @addr: the address to start counting from
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*
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* Unlike change_bit(), this function is non-atomic and may be reordered.
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* If it's called on the same region of memory simultaneously, the effect
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* may be that only one operation succeeds.
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*/
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static __always_inline
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void generic___change_bit(unsigned int nr, volatile unsigned long *addr)
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{
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unsigned long mask = BIT_MASK(nr);
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unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
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*p ^= mask;
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}
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/**
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* generic___test_and_set_bit - Set a bit and return its old value
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* @nr: Bit to set
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* @addr: Address to count from
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*
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* This operation is non-atomic and can be reordered.
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* If two examples of this operation race, one can appear to succeed
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* but actually fail. You must protect multiple accesses with a lock.
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*/
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static __always_inline int
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generic___test_and_set_bit(unsigned int nr, volatile unsigned long *addr)
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{
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unsigned long mask = BIT_MASK(nr);
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unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
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unsigned long old = *p;
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*p = old | mask;
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return (old & mask) != 0;
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}
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/**
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* generic___test_and_clear_bit - Clear a bit and return its old value
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* @nr: Bit to clear
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* @addr: Address to count from
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*
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* This operation is non-atomic and can be reordered.
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* If two examples of this operation race, one can appear to succeed
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* but actually fail. You must protect multiple accesses with a lock.
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*/
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static __always_inline int
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generic___test_and_clear_bit(unsigned int nr, volatile unsigned long *addr)
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{
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unsigned long mask = BIT_MASK(nr);
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unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
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unsigned long old = *p;
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*p = old & ~mask;
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return (old & mask) != 0;
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}
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/* WARNING: non atomic and it can be reordered! */
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static __always_inline int
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generic___test_and_change_bit(unsigned int nr, volatile unsigned long *addr)
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{
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unsigned long mask = BIT_MASK(nr);
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unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
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unsigned long old = *p;
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*p = old ^ mask;
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return (old & mask) != 0;
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}
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/**
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* generic_test_bit - Determine whether a bit is set
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* @nr: bit number to test
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* @addr: Address to start counting from
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*/
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static __always_inline int
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generic_test_bit(unsigned int nr, const volatile unsigned long *addr)
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{
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/*
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* Unlike the bitops with the '__' prefix above, this one *is* atomic,
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* so `volatile` must always stay here with no cast-aways. See
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* `Documentation/atomic_bitops.txt` for the details.
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*/
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return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
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}
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#endif /* __ASM_GENERIC_BITOPS_GENERIC_NON_ATOMIC_H */
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