void
__go_receive_release (struct __go_channel *channel)
{
int i;
if (channel->num_entries != 0)
channel->next_fetch = (channel->next_fetch + 1) % channel->num_entries;
else
{
/* For a synchronous receiver, we tell the sender that we picked
up the value by setting the next_store field back to 0.
Using the mutexes should implement a memory barrier. */
__go_assert (channel->next_store == 1);
channel->next_store = 0;
channel->waiting_to_receive = 0;
}
channel->selected_for_receive = 0;
/* This is a broadcast to make sure that a synchronous sender sees
it. */
i = pthread_cond_broadcast (&channel->cond);
__go_assert (i == 0);
__go_unlock_and_notify_selects (channel);
}
void
__go_builtin_close (struct __go_channel *channel)
{
int i;
i = pthread_mutex_lock (&channel->lock);
__go_assert (i == 0);
while (channel->selected_for_send)
{
i = pthread_cond_wait (&channel->cond, &channel->lock);
__go_assert (i == 0);
}
if (channel->is_closed)
{
i = pthread_mutex_unlock (&channel->lock);
__go_assert (i == 0);
__go_panic_msg ("close of closed channel");
}
channel->is_closed = 1;
i = pthread_cond_broadcast (&channel->cond);
__go_assert (i == 0);
__go_unlock_and_notify_selects (channel);
}
_Bool
__go_receive_acquire (struct __go_channel *channel, _Bool for_select)
{
int i;
_Bool my_wait_lock;
_Bool synched_with_select;
my_wait_lock = 0;
synched_with_select = 0;
i = pthread_mutex_lock (&channel->lock);
__go_assert (i == 0);
while (1)
{
_Bool need_broadcast;
need_broadcast = 0;
/* Check whether the channel is closed. */
if (channel->is_closed
&& (channel->num_entries == 0
? channel->next_store == 0
: channel->next_fetch == channel->next_store))
{
channel->selected_for_receive = 0;
__go_unlock_and_notify_selects (channel);
return 0;
}
/* If somebody else has the channel locked for receiving, we
have to wait. If FOR_SELECT is true, then we are the one
with the lock. */
if (!channel->selected_for_receive || for_select)
{
if (channel->num_entries == 0)
{
/* If somebody else is waiting to receive, we have to
wait. */
if (!channel->waiting_to_receive || my_wait_lock)
{
_Bool was_marked;
/* Lock the channel so that we get to receive
next. */
was_marked = channel->waiting_to_receive;
channel->waiting_to_receive = 1;
my_wait_lock = 1;
/* See if there is a value to receive. */
if (channel->next_store > 0)
return 1;
/* If we haven't already done so, try to synch with
a select waiting to send on this channel. If we
have already synched with a select, we are just
looping until the select eventually causes
something to be sent. */
if (!synched_with_select && !for_select)
{
if (__go_synch_with_select (channel, 0))
{
synched_with_select = 1;
need_broadcast = 1;
}
}
/* If we marked the channel as waiting, we need to
signal, because something changed. It needs to
be a broadcast since there might be other
receivers waiting. */
if (!was_marked)
{
i = pthread_cond_broadcast (&channel->cond);
__go_assert (i == 0);
}
}
}
else
{
/* If there is a value on the channel, we are OK. */
if (channel->next_fetch != channel->next_store)
return 1;
}
}
/* If we just synched with a select, then we need to signal the
select condition variable. We can only do that if we unlock
the channel. So we need to unlock, signal, lock, and go
around the loop again without waiting. */
if (need_broadcast)
{
__go_broadcast_to_select (channel);
continue;
}
/* Wait for something to change, then loop around and try
again. */
i = pthread_cond_wait (&channel->cond, &channel->lock);
__go_assert (i == 0);
}
}
void
__go_send_release (struct __go_channel *channel)
{
int i;
if (channel->num_entries != 0)
{
/* This is a buffered channel. Bump the store count and signal
the condition variable. */
channel->next_store = (channel->next_store + 1) % channel->num_entries;
i = pthread_cond_signal (&channel->cond);
__go_assert (i == 0);
}
else
{
_Bool synched_with_select;
/* This is a synchronous channel. Indicate that we have a value
waiting. */
channel->next_store = 1;
channel->waiting_to_send = 1;
/* Tell everybody else to do something. This has to be a
broadcast because we might have both senders and receivers
waiting on the condition, but senders won't send another
signal. */
i = pthread_cond_broadcast (&channel->cond);
__go_assert (i == 0);
/* Wait until the value is received. */
synched_with_select = 0;
while (1)
{
if (channel->next_store == 0)
break;
/* If nobody is currently waiting to receive, try to synch
up with a select. */
if (!channel->waiting_to_receive && !synched_with_select)
{
if (__go_synch_with_select (channel, 1))
{
synched_with_select = 1;
__go_broadcast_to_select (channel);
continue;
}
}
i = pthread_cond_wait (&channel->cond, &channel->lock);
__go_assert (i == 0);
}
channel->waiting_to_send = 0;
/* Using the mutexes should implement a memory barrier. */
/* We have to signal again since we cleared the waiting_to_send
field. This has to be a broadcast because both senders and
receivers might be waiting, but only senders will be able to
act. */
i = pthread_cond_broadcast (&channel->cond);
__go_assert (i == 0);
}
channel->selected_for_send = 0;
__go_unlock_and_notify_selects (channel);
}
