criu/include/lock.h

#ifndef __CR_LOCK_H__
#define __CR_LOCK_H__

#include <linux/futex.h>
#include <sys/time.h>
#include <limits.h>
#include <errno.h>

#include "asm/types.h"
#include "asm/atomic.h"
#include "syscall.h"
#include "bug.h"

typedef struct {
	atomic_t raw;
} futex_t;

#define FUTEX_ABORT_FLAG	(0x80000000)
#define FUTEX_ABORT_RAW		(-1U)

/* Get current futex @f value */
static inline u32 futex_get(futex_t *f)
{
	return atomic_get(&f->raw);
}

/* Set futex @f value to @v */
static inline void futex_set(futex_t *f, u32 v)
{
	atomic_set(&f->raw, (int)v);
}

#define futex_init(f)	futex_set(f, 0)

/* Wait on futex @__f value @__v become in condition @__c */
#define futex_wait_if_cond(__f, __v, __cond)			\
	do {							\
		int ret;					\
		u32 tmp;					\
								\
		while (1) {					\
			tmp = (u32)atomic_get(&(__f)->raw);	\
			if ((tmp & FUTEX_ABORT_FLAG) ||		\
			    (tmp __cond (__v)))			\
				break;				\
			ret = sys_futex((u32 *)&(__f)->raw.counter, FUTEX_WAIT,\
					tmp, NULL, NULL, 0);	\
			BUG_ON(ret < 0 && ret != -EWOULDBLOCK);	\
		}						\
	} while (0)

/* Set futex @f to @v and wake up all waiters */
static inline void futex_set_and_wake(futex_t *f, u32 v)
{
	atomic_set(&f->raw, (int)v);
	BUG_ON(sys_futex((u32 *)&f->raw.counter, FUTEX_WAKE, INT_MAX, NULL, NULL, 0) < 0);
}

/* Mark futex @f as wait abort needed and wake up all waiters */
static inline void futex_abort_and_wake(futex_t *f)
{
	BUILD_BUG_ON(!(FUTEX_ABORT_RAW & FUTEX_ABORT_FLAG));
	futex_set_and_wake(f, FUTEX_ABORT_RAW);
}

/* Decrement futex @f value and wake up all waiters */
static inline void futex_dec_and_wake(futex_t *f)
{
	atomic_dec(&f->raw);
	BUG_ON(sys_futex((u32 *)&f->raw.counter, FUTEX_WAKE, INT_MAX, NULL, NULL, 0) < 0);
}

/* Increment futex @f value and wake up all waiters */
static inline void futex_inc_and_wake(futex_t *f)
{
	atomic_inc(&f->raw);
	BUG_ON(sys_futex((u32 *)&f->raw.counter, FUTEX_WAKE, INT_MAX, NULL, NULL, 0) < 0);
}

/* Plain increment futex @f value */
static inline void futex_inc(futex_t *f) { atomic_inc(&f->raw); }

/* Plain decrement futex @f value */
static inline void futex_dec(futex_t *f) { atomic_dec(&f->raw); }

/* Wait until futex @f value become @v */
static inline void futex_wait_until(futex_t *f, u32 v)
{ futex_wait_if_cond(f, v, ==); }

/* Wait while futex @f value is greater than @v */
static inline void futex_wait_while_gt(futex_t *f, u32 v)
{ futex_wait_if_cond(f, v, <=); }

/* Wait while futex @f value is less than @v */
static inline void futex_wait_while_lt(futex_t *f, u32 v)
{ futex_wait_if_cond(f, v, >=); }

/* Wait while futex @f value is equal to @v */
static inline void futex_wait_while_eq(futex_t *f, u32 v)
{ futex_wait_if_cond(f, v, !=); }

/* Wait while futex @f value is @v */
static inline void futex_wait_while(futex_t *f, u32 v)
{
	while ((u32)atomic_get(&f->raw) == v) {
		int ret = sys_futex((u32 *)&f->raw.counter, FUTEX_WAIT, v, NULL, NULL, 0);
		BUG_ON(ret < 0 && ret != -EWOULDBLOCK);
	}
}

typedef struct {
	atomic_t	raw;
} mutex_t;

static inline void mutex_init(mutex_t *m)
{
	u32 c = 0;
	atomic_set(&m->raw, (int)c);
}

static inline void mutex_lock(mutex_t *m)
{
	u32 c;
	int ret;

	while ((c = (u32)atomic_inc_return(&m->raw)) != 1) {
		ret = sys_futex((u32 *)&m->raw.counter, FUTEX_WAIT, c, NULL, NULL, 0);
		BUG_ON(ret < 0 && ret != -EWOULDBLOCK);
	}
}

static inline void mutex_unlock(mutex_t *m)
{
	u32 c = 0;
	atomic_set(&m->raw, (int)c);
	BUG_ON(sys_futex((u32 *)&m->raw.counter, FUTEX_WAKE, 1, NULL, NULL, 0) < 0);
}

#endif /* __CR_LOCK_H__ */