int _DkInternalLock (PAL_LOCK* lock) {
while (_DkMutexLock(lock) < 0); // Retry the lock if being interrupted by signals
return 0;
}
int _DkMutexLockTimeout (struct mutex_handle * mut, int timeout)
{
int i, c = 0;
if (timeout == -1)
return -_DkMutexLock(mut);
struct atomic_int * m = &mut->value;
/* Spin and try to take lock */
for (i = 0 ; i < MUTEX_SPINLOCK_TIMES ; i++)
{
c = atomic_dec_and_test(m);
if (c)
goto success;
cpu_relax();
}
/* The lock is now contended */
int ret;
if (timeout == 0) {
ret = c ? 0 : -PAL_ERROR_TRYAGAIN;
goto out;
}
while (!c) {
int val = atomic_read(m);
if (val == 1)
goto again;
struct timespec waittime;
long sec = timeout / 1000000;
long microsec = timeout - (sec * 1000000);
waittime.tv_sec = sec;
waittime.tv_nsec = microsec * 1000;
ret = INLINE_SYSCALL(futex, 6, m, FUTEX_WAIT, val, &waittime, NULL, 0);
if (IS_ERR(ret) &&
ERRNO(ret) != EWOULDBLOCK &&
ERRNO(ret) != EINTR) {
ret = unix_to_pal_error(ERRNO(ret));
goto out;
}
#ifdef DEBUG_MUTEX
if (IS_ERR(ret))
printf("mutex held by thread %d\n", mut->owner);
#endif
again:
/* Upon wakeup, we still need to check whether mutex is unlocked or
* someone else took it.
* If c==0 upon return from xchg (i.e., the older value of m==0), we
* will exit the loop. Else, we sleep again (through a futex call).
*/
c = atomic_dec_and_test(m);
}
success:
#ifdef DEBUG_MUTEX
mut->owner = INLINE_SYSCALL(gettid, 0);
#endif
ret = 0;
out:
return ret;
}