arch/s390/include/asm/preempt.h

Source file repositories/reference/linux-study-clean/arch/s390/include/asm/preempt.h

File Facts

System
Linux kernel
Corpus path
arch/s390/include/asm/preempt.h
Extension
.h
Size
4975 bytes
Lines
168
Domain
Architecture Layer
Bucket
arch/s390
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

if (__builtin_constant_p(val) && (val >= -128) && (val <= 127)) {
			unsigned long lc_preempt;

			lc_preempt = offsetof(struct lowcore, preempt_count);
			asm_inline(
				ALTERNATIVE("asi	%[offzero](%%r0),%[val]\n",
					    "asi	%[offalt](%%r0),%[val]\n",
					    ALT_FEATURE(MFEATURE_LOWCORE))
				: "+m" (((struct lowcore *)0)->preempt_count)
				: [offzero] "i" (lc_preempt), [val] "i" (val),
				  [offalt] "i" (lc_preempt + LOWCORE_ALT_ADDRESS)
				: "cc");
			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)
{
#ifdef __HAVE_ASM_FLAG_OUTPUTS__
	unsigned long lc_preempt;
	int cc;

	lc_preempt = offsetof(struct lowcore, preempt_count);
	asm_inline(
		ALTERNATIVE("alsi	%[offzero](%%r0),%[val]\n",
			    "alsi	%[offalt](%%r0),%[val]\n",
			    ALT_FEATURE(MFEATURE_LOWCORE))
		: "=@cc" (cc), "+m" (((struct lowcore *)0)->preempt_count)
		: [offzero] "i" (lc_preempt), [val] "i" (-1),
		[offalt] "i" (lc_preempt + LOWCORE_ALT_ADDRESS));
	return (cc == 0) || (cc == 2);
#else
	return __atomic_add_const_and_test(-1, &get_lowcore()->preempt_count);
#endif
}

/*
 * 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 */

Annotation

Implementation Notes