/*
* Routine: ipc_mqueue_post
* Purpose:
* Post a message to a waiting receiver or enqueue it. If a
* receiver is waiting, we can release our reserved space in
* the message queue.
*
* Conditions:
* If we need to queue, our space in the message queue is reserved.
*/
void
ipc_mqueue_post(
register ipc_mqueue_t mqueue,
register ipc_kmsg_t kmsg)
{
spl_t s;
/*
* While the msg queue is locked, we have control of the
* kmsg, so the ref in it for the port is still good.
*
* Check for a receiver for the message.
*/
s = splsched();
imq_lock(mqueue);
for (;;) {
wait_queue_t waitq = &mqueue->imq_wait_queue;
thread_t receiver;
mach_msg_size_t msize;
receiver = wait_queue_wakeup64_identity_locked(
waitq,
IPC_MQUEUE_RECEIVE,
THREAD_AWAKENED,
FALSE);
/* waitq still locked, thread locked */
if (receiver == THREAD_NULL) {
/*
* no receivers; queue kmsg
*/
assert(mqueue->imq_msgcount > 0);
ipc_kmsg_enqueue_macro(&mqueue->imq_messages, kmsg);
break;
}
/*
* If the receiver waited with a facility not directly
* related to Mach messaging, then it isn't prepared to get
* handed the message directly. Just set it running, and
* go look for another thread that can.
*/
if (receiver->ith_state != MACH_RCV_IN_PROGRESS) {
thread_unlock(receiver);
continue;
}
/*
* We found a waiting thread.
* If the message is too large or the scatter list is too small
* the thread we wake up will get that as its status.
*/
msize = ipc_kmsg_copyout_size(kmsg, receiver->map);
if (receiver->ith_msize <
(msize + REQUESTED_TRAILER_SIZE(thread_is_64bit(receiver), receiver->ith_option))) {
receiver->ith_msize = msize;
receiver->ith_state = MACH_RCV_TOO_LARGE;
} else {
receiver->ith_state = MACH_MSG_SUCCESS;
}
/*
* If there is no problem with the upcoming receive, or the
* receiver thread didn't specifically ask for special too
* large error condition, go ahead and select it anyway.
*/
if ((receiver->ith_state == MACH_MSG_SUCCESS) ||
!(receiver->ith_option & MACH_RCV_LARGE)) {
receiver->ith_kmsg = kmsg;
receiver->ith_seqno = mqueue->imq_seqno++;
thread_unlock(receiver);
/* we didn't need our reserved spot in the queue */
ipc_mqueue_release_msgcount(mqueue);
break;
}
/*
* Otherwise, this thread needs to be released to run
* and handle its error without getting the message. We
* need to go back and pick another one.
*/
receiver->ith_receiver_name = mqueue->imq_receiver_name;
receiver->ith_kmsg = IKM_NULL;
receiver->ith_seqno = 0;
thread_unlock(receiver);
}
imq_unlock(mqueue);
splx(s);
current_task()->messages_sent++;
return;
}
mach_msg_return_t
ipc_mqueue_send(
ipc_kmsg_t kmsg,
mach_msg_option_t option,
mach_msg_timeout_t time_out)
{
ipc_port_t port;
port = (ipc_port_t) kmsg->ikm_header.msgh_remote_port;
assert(IP_VALID(port));
ip_lock(port);
if (port->ip_receiver == ipc_space_kernel) {
ipc_kmsg_t reply;
/*
* We can check ip_receiver == ipc_space_kernel
* before checking that the port is active because
* ipc_port_dealloc_kernel clears ip_receiver
* before destroying a kernel port.
*/
assert(ip_active(port));
ip_unlock(port);
reply = ipc_kobject_server(kmsg);
if (reply != IKM_NULL)
ipc_mqueue_send_always(reply);
return MACH_MSG_SUCCESS;
}
for (;;) {
ipc_thread_t self;
/*
* Can't deliver to a dead port.
* However, we can pretend it got sent
* and was then immediately destroyed.
*/
if (!ip_active(port)) {
/*
* We can't let ipc_kmsg_destroy deallocate
* the port right, because we might end up
* in an infinite loop trying to deliver
* a send-once notification.
*/
ip_release(port);
ip_check_unlock(port);
kmsg->ikm_header.msgh_remote_port = MACH_PORT_NULL;
ipc_kmsg_destroy(kmsg);
return MACH_MSG_SUCCESS;
}
/*
* Don't block if:
* 1) We're under the queue limit.
* 2) Caller used the MACH_SEND_ALWAYS internal option.
* 3) Message is sent to a send-once right.
*/
if ((port->ip_msgcount < port->ip_qlimit) ||
(option & MACH_SEND_ALWAYS) ||
(MACH_MSGH_BITS_REMOTE(kmsg->ikm_header.msgh_bits) ==
MACH_MSG_TYPE_PORT_SEND_ONCE))
break;
/* must block waiting for queue to clear */
self = current_thread();
if (option & MACH_SEND_TIMEOUT) {
if (time_out == 0) {
ip_unlock(port);
return MACH_SEND_TIMED_OUT;
}
thread_will_wait_with_timeout(self, time_out);
} else
thread_will_wait(self);
ipc_thread_enqueue(&port->ip_blocked, self);
self->ith_state = MACH_SEND_IN_PROGRESS;
ip_unlock(port);
counter(c_ipc_mqueue_send_block++);
thread_block((void (*)(void)) 0);
ip_lock(port);
/* why did we wake up? */
if (self->ith_state == MACH_MSG_SUCCESS)
continue;
assert(self->ith_state == MACH_SEND_IN_PROGRESS);
/* take ourselves off blocked queue */
ipc_thread_rmqueue(&port->ip_blocked, self);
/*
* Thread wakeup-reason field tells us why
* the wait was interrupted.
*/
switch (self->ith_wait_result) {
case THREAD_INTERRUPTED:
/* send was interrupted - give up */
ip_unlock(port);
return MACH_SEND_INTERRUPTED;
case THREAD_TIMED_OUT:
/* timeout expired */
assert(option & MACH_SEND_TIMEOUT);
time_out = 0;
break;
case THREAD_RESTART:
default:
#if MACH_ASSERT
assert(!"ipc_mqueue_send");
#else
panic("ipc_mqueue_send");
#endif
}
}
if (kmsg->ikm_header.msgh_bits & MACH_MSGH_BITS_CIRCULAR) {
ip_unlock(port);
/* don't allow the creation of a circular loop */
ipc_kmsg_destroy(kmsg);
return MACH_MSG_SUCCESS;
}
{
ipc_mqueue_t mqueue;
ipc_pset_t pset;
ipc_thread_t receiver;
ipc_thread_queue_t receivers;
port->ip_msgcount++;
assert(port->ip_msgcount > 0);
pset = port->ip_pset;
if (pset == IPS_NULL)
mqueue = &port->ip_messages;
else
mqueue = &pset->ips_messages;
imq_lock(mqueue);
receivers = &mqueue->imq_threads;
/*
* Can unlock the port now that the msg queue is locked
* and we know the port is active. While the msg queue
* is locked, we have control of the kmsg, so the ref in
* it for the port is still good. If the msg queue is in
* a set (dead or alive), then we're OK because the port
* is still a member of the set and the set won't go away
* until the port is taken out, which tries to lock the
* set's msg queue to remove the port's msgs.
*/
ip_unlock(port);
/* check for a receiver for the message */
for (;;) {
receiver = ipc_thread_queue_first(receivers);
if (receiver == ITH_NULL) {
/* no receivers; queue kmsg */
ipc_kmsg_enqueue_macro(&mqueue->imq_messages, kmsg);
imq_unlock(mqueue);
break;
}
ipc_thread_rmqueue_first_macro(receivers, receiver);
assert(ipc_kmsg_queue_empty(&mqueue->imq_messages));
if (kmsg->ikm_header.msgh_size <= receiver->ith_msize) {
/* got a successful receiver */
receiver->ith_state = MACH_MSG_SUCCESS;
receiver->ith_kmsg = kmsg;
receiver->ith_seqno = port->ip_seqno++;
imq_unlock(mqueue);
thread_go(receiver);
break;
}
receiver->ith_state = MACH_RCV_TOO_LARGE;
receiver->ith_msize = kmsg->ikm_header.msgh_size;
thread_go(receiver);
}
}
current_task()->messages_sent++;
return MACH_MSG_SUCCESS;
}
