mirror of
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-08-05 16:54:27 +00:00
5c9e37e523
Use __atomic_add_const_and_test() within __preempt_count_dec_and_test(). With this it is possible to decrease preempt_count by one and test if need_resched is set with one instruction, if the compiler has support for flag output operand constraints. Reviewed-by: Juergen Christ <jchrist@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
126 lines
3.5 KiB
C
126 lines
3.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef __ASM_PREEMPT_H
|
|
#define __ASM_PREEMPT_H
|
|
|
|
#include <asm/current.h>
|
|
#include <linux/thread_info.h>
|
|
#include <asm/atomic_ops.h>
|
|
#include <asm/cmpxchg.h>
|
|
#include <asm/march.h>
|
|
|
|
/* We use the MSB mostly because its available */
|
|
#define PREEMPT_NEED_RESCHED 0x80000000
|
|
|
|
/*
|
|
* We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such
|
|
* that a decrement hitting 0 means we can and should reschedule.
|
|
*/
|
|
#define PREEMPT_ENABLED (0 + PREEMPT_NEED_RESCHED)
|
|
|
|
/*
|
|
* We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users
|
|
* that think a non-zero value indicates we cannot preempt.
|
|
*/
|
|
static __always_inline int preempt_count(void)
|
|
{
|
|
return READ_ONCE(get_lowcore()->preempt_count) & ~PREEMPT_NEED_RESCHED;
|
|
}
|
|
|
|
static __always_inline void preempt_count_set(int pc)
|
|
{
|
|
int old, new;
|
|
|
|
old = READ_ONCE(get_lowcore()->preempt_count);
|
|
do {
|
|
new = (old & PREEMPT_NEED_RESCHED) | (pc & ~PREEMPT_NEED_RESCHED);
|
|
} while (!arch_try_cmpxchg(&get_lowcore()->preempt_count, &old, new));
|
|
}
|
|
|
|
/*
|
|
* We fold the NEED_RESCHED bit into the preempt count such that
|
|
* preempt_enable() can decrement and test for needing to reschedule with a
|
|
* short instruction sequence.
|
|
*
|
|
* We invert the actual bit, so that when the decrement hits 0 we know we both
|
|
* need to resched (the bit is cleared) and can resched (no preempt count).
|
|
*/
|
|
|
|
static __always_inline void set_preempt_need_resched(void)
|
|
{
|
|
__atomic_and(~PREEMPT_NEED_RESCHED, &get_lowcore()->preempt_count);
|
|
}
|
|
|
|
static __always_inline void clear_preempt_need_resched(void)
|
|
{
|
|
__atomic_or(PREEMPT_NEED_RESCHED, &get_lowcore()->preempt_count);
|
|
}
|
|
|
|
static __always_inline bool test_preempt_need_resched(void)
|
|
{
|
|
return !(READ_ONCE(get_lowcore()->preempt_count) & PREEMPT_NEED_RESCHED);
|
|
}
|
|
|
|
static __always_inline void __preempt_count_add(int val)
|
|
{
|
|
/*
|
|
* With some obscure config options and CONFIG_PROFILE_ALL_BRANCHES
|
|
* enabled, gcc 12 fails to handle __builtin_constant_p().
|
|
*/
|
|
if (!IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES)) {
|
|
if (__builtin_constant_p(val) && (val >= -128) && (val <= 127)) {
|
|
__atomic_add_const(val, &get_lowcore()->preempt_count);
|
|
return;
|
|
}
|
|
}
|
|
__atomic_add(val, &get_lowcore()->preempt_count);
|
|
}
|
|
|
|
static __always_inline void __preempt_count_sub(int val)
|
|
{
|
|
__preempt_count_add(-val);
|
|
}
|
|
|
|
/*
|
|
* Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule
|
|
* a decrement which hits zero means we have no preempt_count and should
|
|
* reschedule.
|
|
*/
|
|
static __always_inline bool __preempt_count_dec_and_test(void)
|
|
{
|
|
return __atomic_add_const_and_test(-1, &get_lowcore()->preempt_count);
|
|
}
|
|
|
|
/*
|
|
* Returns true when we need to resched and can (barring IRQ state).
|
|
*/
|
|
static __always_inline bool should_resched(int preempt_offset)
|
|
{
|
|
return unlikely(READ_ONCE(get_lowcore()->preempt_count) == preempt_offset);
|
|
}
|
|
|
|
#define init_task_preempt_count(p) do { } while (0)
|
|
/* Deferred to CPU bringup time */
|
|
#define init_idle_preempt_count(p, cpu) do { } while (0)
|
|
|
|
#ifdef CONFIG_PREEMPTION
|
|
|
|
void preempt_schedule(void);
|
|
void preempt_schedule_notrace(void);
|
|
|
|
#ifdef CONFIG_PREEMPT_DYNAMIC
|
|
|
|
void dynamic_preempt_schedule(void);
|
|
void dynamic_preempt_schedule_notrace(void);
|
|
#define __preempt_schedule() dynamic_preempt_schedule()
|
|
#define __preempt_schedule_notrace() dynamic_preempt_schedule_notrace()
|
|
|
|
#else /* CONFIG_PREEMPT_DYNAMIC */
|
|
|
|
#define __preempt_schedule() preempt_schedule()
|
|
#define __preempt_schedule_notrace() preempt_schedule_notrace()
|
|
|
|
#endif /* CONFIG_PREEMPT_DYNAMIC */
|
|
|
|
#endif /* CONFIG_PREEMPTION */
|
|
|
|
#endif /* __ASM_PREEMPT_H */
|