void object_lock_exclusive_(IObject *thiz, const char *file, int line)
{
int ok;
ok = pthread_mutex_trylock(&thiz->mMutex);
if (0 != ok) {
// not android_atomic_acquire_load because we don't care about relative load/load ordering
int32_t oldGeneration = thiz->mGeneration;
// wait up to a total of 250 ms
static const long nanoBackoffs[] = {
10 * 1000000, 20 * 1000000, 30 * 1000000, 40 * 1000000, 50 * 1000000, 100 * 1000000};
unsigned i = 0;
timespec ts;
memset(&ts, 0, sizeof(timespec));
for (;;) {
init_time_spec(&ts, nanoBackoffs[i]);
ok = pthread_mutex_timedlock(&thiz->mMutex, &ts);
if (0 == ok) {
break;
}
if (EBUSY == ok) {
// this is the expected return value for timeout, and will be handled below
} else if (EDEADLK == ok) {
// we don't use the kind of mutex that can return this error, but just in case
SL_LOGE("%s:%d: recursive lock detected", file, line);
} else {
// some other return value
SL_LOGE("%s:%d: pthread_mutex_lock_timeout_np returned %d", file, line, ok);
}
// is anyone else making forward progress?
int32_t newGeneration = thiz->mGeneration;
if (newGeneration != oldGeneration) {
// if we ever see forward progress then lock without timeout (more efficient)
goto forward_progress;
}
// no, then continue trying to lock but with increasing timeouts
if (++i >= (sizeof(nanoBackoffs) / sizeof(nanoBackoffs[0]))) {
// the extra block avoids a C++ compiler error about goto past initialization
{
pthread_t me = pthread_self();
pthread_t owner = thiz->mOwner;
// unlikely, but this could result in a memory fault if owner is corrupt
pid_t ownerTid = LIKELY_VALID(owner) ? __pthread_gettid(owner) : -1;
SL_LOGW("%s:%d: pthread %p (tid %d) sees object %p was locked by pthread %p"
" (tid %d) at %s:%d\n", file, line, *(void **)&me, gettid(), thiz,
*(void **)&owner, ownerTid, thiz->mFile, thiz->mLine);
}
forward_progress:
// attempt one more time without timeout; maybe this time we will be successful
ok = pthread_mutex_lock(&thiz->mMutex);
assert(0 == ok);
break;
}
}
}
// here if mutex was successfully locked
pthread_t zero;
memset(&zero, 0, sizeof(pthread_t));
if (0 != memcmp(&zero, &thiz->mOwner, sizeof(pthread_t))) {
pthread_t me = pthread_self();
pthread_t owner = thiz->mOwner;
pid_t ownerTid = LIKELY_VALID(owner) ? __pthread_gettid(owner) : -1;
if (pthread_equal(pthread_self(), owner)) {
SL_LOGE("%s:%d: pthread %p (tid %d) sees object %p was recursively locked by pthread"
" %p (tid %d) at %s:%d\n", file, line, *(void **)&me, gettid(), thiz,
*(void **)&owner, ownerTid, thiz->mFile, thiz->mLine);
} else {
SL_LOGE("%s:%d: pthread %p (tid %d) sees object %p was left unlocked in unexpected"
" state by pthread %p (tid %d) at %s:%d\n", file, line, *(void **)&me, gettid(),
thiz, *(void **)&owner, ownerTid, thiz->mFile, thiz->mLine);
}
assert(false);
}
thiz->mOwner = pthread_self();
thiz->mFile = file;
thiz->mLine = line;
// not android_atomic_inc because we are already holding a mutex
++thiz->mGeneration;
}
// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_create.html
int timer_create(clockid_t clock_id, sigevent* evp, timer_t* timer_id) {
PosixTimer* timer = reinterpret_cast<PosixTimer*>(malloc(sizeof(PosixTimer)));
if (timer == NULL) {
return -1;
}
timer->sigev_notify = (evp == NULL) ? SIGEV_SIGNAL : evp->sigev_notify;
// If not a SIGEV_THREAD timer, the kernel can handle it without our help.
if (timer->sigev_notify != SIGEV_THREAD) {
if (__timer_create(clock_id, evp, &timer->kernel_timer_id) == -1) {
free(timer);
return -1;
}
*timer_id = timer;
return 0;
}
// Otherwise, this must be SIGEV_THREAD timer...
timer->callback = evp->sigev_notify_function;
timer->callback_argument = evp->sigev_value;
// Check arguments that the kernel doesn't care about but we do.
if (timer->callback == NULL) {
free(timer);
errno = EINVAL;
return -1;
}
// Create this timer's thread.
pthread_attr_t thread_attributes;
if (evp->sigev_notify_attributes == NULL) {
pthread_attr_init(&thread_attributes);
} else {
thread_attributes = *reinterpret_cast<pthread_attr_t*>(evp->sigev_notify_attributes);
}
pthread_attr_setdetachstate(&thread_attributes, PTHREAD_CREATE_DETACHED);
// We start the thread with TIMER_SIGNAL blocked by blocking the signal here and letting it
// inherit. If it tried to block the signal itself, there would be a race.
kernel_sigset_t sigset;
sigaddset(sigset.get(), TIMER_SIGNAL);
kernel_sigset_t old_sigset;
pthread_sigmask(SIG_BLOCK, sigset.get(), old_sigset.get());
int rc = pthread_create(&timer->callback_thread, &thread_attributes, __timer_thread_start, timer);
pthread_sigmask(SIG_SETMASK, old_sigset.get(), NULL);
if (rc != 0) {
free(timer);
errno = rc;
return -1;
}
sigevent se = *evp;
se.sigev_signo = TIMER_SIGNAL;
se.sigev_notify = SIGEV_THREAD_ID;
se.sigev_notify_thread_id = __pthread_gettid(timer->callback_thread);
if (__timer_create(clock_id, &se, &timer->kernel_timer_id) == -1) {
__timer_thread_stop(timer);
return -1;
}
// Give the thread a meaningful name.
// It can't do this itself because the kernel timer isn't created until after it's running.
char name[32];
snprintf(name, sizeof(name), "POSIX interval timer %d", to_kernel_timer_id(timer));
pthread_setname_np(timer->callback_thread, name);
*timer_id = timer;
return 0;
}
