mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-11-28 14:44:10 +08:00
cf3ee3c8c2
Now that all architectures provide arch_atomic_long_*(), we can implement the generic bitops atop these rather than atop atomic_long_*(), and provide arch_*() forms of the bitops that are safe to use in noinstr code. Now that all architectures provide arch_atomic_long_*(), we can build the generic arch_*() bitops atop these, which can be safely used in noinstr code. The regular bitop wrappers are built atop these. As the generic non-atomic bitops use plain accesses, these will be implicitly instrumented unless they are inlined into noinstr functions (which is similar to arch_atomic*_read() when based on READ_ONCE()). The wrappers are modified so that where the underlying arch_*() function uses a plain access, no explicit instrumentation is added, as this is redundant and could result in confusing reports. Since function prototypes get excessively long with both an `arch_` prefix and `__always_inline` attribute, the return type and function attributes have been split onto a separate line, matching the style of the generated atomic headers. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20210713105253.7615-6-mark.rutland@arm.com
95 lines
2.6 KiB
C
95 lines
2.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef _ASM_GENERIC_BITOPS_LOCK_H_
|
|
#define _ASM_GENERIC_BITOPS_LOCK_H_
|
|
|
|
#include <linux/atomic.h>
|
|
#include <linux/compiler.h>
|
|
#include <asm/barrier.h>
|
|
|
|
/**
|
|
* arch_test_and_set_bit_lock - Set a bit and return its old value, for lock
|
|
* @nr: Bit to set
|
|
* @addr: Address to count from
|
|
*
|
|
* This operation is atomic and provides acquire barrier semantics if
|
|
* the returned value is 0.
|
|
* It can be used to implement bit locks.
|
|
*/
|
|
static __always_inline int
|
|
arch_test_and_set_bit_lock(unsigned int nr, volatile unsigned long *p)
|
|
{
|
|
long old;
|
|
unsigned long mask = BIT_MASK(nr);
|
|
|
|
p += BIT_WORD(nr);
|
|
if (READ_ONCE(*p) & mask)
|
|
return 1;
|
|
|
|
old = arch_atomic_long_fetch_or_acquire(mask, (atomic_long_t *)p);
|
|
return !!(old & mask);
|
|
}
|
|
|
|
|
|
/**
|
|
* arch_clear_bit_unlock - Clear a bit in memory, for unlock
|
|
* @nr: the bit to set
|
|
* @addr: the address to start counting from
|
|
*
|
|
* This operation is atomic and provides release barrier semantics.
|
|
*/
|
|
static __always_inline void
|
|
arch_clear_bit_unlock(unsigned int nr, volatile unsigned long *p)
|
|
{
|
|
p += BIT_WORD(nr);
|
|
arch_atomic_long_fetch_andnot_release(BIT_MASK(nr), (atomic_long_t *)p);
|
|
}
|
|
|
|
/**
|
|
* arch___clear_bit_unlock - Clear a bit in memory, for unlock
|
|
* @nr: the bit to set
|
|
* @addr: the address to start counting from
|
|
*
|
|
* A weaker form of clear_bit_unlock() as used by __bit_lock_unlock(). If all
|
|
* the bits in the word are protected by this lock some archs can use weaker
|
|
* ops to safely unlock.
|
|
*
|
|
* See for example x86's implementation.
|
|
*/
|
|
static inline void
|
|
arch___clear_bit_unlock(unsigned int nr, volatile unsigned long *p)
|
|
{
|
|
unsigned long old;
|
|
|
|
p += BIT_WORD(nr);
|
|
old = READ_ONCE(*p);
|
|
old &= ~BIT_MASK(nr);
|
|
arch_atomic_long_set_release((atomic_long_t *)p, old);
|
|
}
|
|
|
|
/**
|
|
* arch_clear_bit_unlock_is_negative_byte - Clear a bit in memory and test if bottom
|
|
* byte is negative, for unlock.
|
|
* @nr: the bit to clear
|
|
* @addr: the address to start counting from
|
|
*
|
|
* This is a bit of a one-trick-pony for the filemap code, which clears
|
|
* PG_locked and tests PG_waiters,
|
|
*/
|
|
#ifndef arch_clear_bit_unlock_is_negative_byte
|
|
static inline bool arch_clear_bit_unlock_is_negative_byte(unsigned int nr,
|
|
volatile unsigned long *p)
|
|
{
|
|
long old;
|
|
unsigned long mask = BIT_MASK(nr);
|
|
|
|
p += BIT_WORD(nr);
|
|
old = arch_atomic_long_fetch_andnot_release(mask, (atomic_long_t *)p);
|
|
return !!(old & BIT(7));
|
|
}
|
|
#define arch_clear_bit_unlock_is_negative_byte arch_clear_bit_unlock_is_negative_byte
|
|
#endif
|
|
|
|
#include <asm-generic/bitops/instrumented-lock.h>
|
|
|
|
#endif /* _ASM_GENERIC_BITOPS_LOCK_H_ */
|