mars/kernel/lamport.c

50 lines
1.0 KiB
C
Raw Normal View History

2013-07-18 10:45:34 +00:00
// (c) 2010 Thomas Schoebel-Theuer / 1&1 Internet AG
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/semaphore.h>
#include "lamport.h"
struct semaphore lamport_sem = __SEMAPHORE_INITIALIZER(lamport_sem, 1); // TODO: replace with spinlock if possible (first check)
struct timespec lamport_now = {};
void get_lamport(struct timespec *now)
{
int diff;
down(&lamport_sem);
*now = CURRENT_TIME;
diff = timespec_compare(now, &lamport_now);
if (diff >= 0) {
timespec_add_ns(now, 1);
memcpy(&lamport_now, now, sizeof(lamport_now));
timespec_add_ns(&lamport_now, 1);
} else {
timespec_add_ns(&lamport_now, 1);
memcpy(now, &lamport_now, sizeof(*now));
}
up(&lamport_sem);
}
EXPORT_SYMBOL_GPL(get_lamport);
void set_lamport(struct timespec *old)
{
int diff;
down(&lamport_sem);
diff = timespec_compare(old, &lamport_now);
if (diff >= 0) {
memcpy(&lamport_now, old, sizeof(lamport_now));
timespec_add_ns(&lamport_now, 1);
}
up(&lamport_sem);
}
EXPORT_SYMBOL_GPL(set_lamport);