int32_t _timeout_remaining_get(struct _timeout *timeout)
{
unsigned int key = irq_lock();
int32_t remaining_ticks;
if (timeout->delta_ticks_from_prev == _INACTIVE) {
remaining_ticks = 0;
} else {
/*
* compute remaining ticks by walking the timeout list
* and summing up the various tick deltas involved
*/
struct _timeout *t =
(struct _timeout *)sys_dlist_peek_head(&_timeout_q);
remaining_ticks = t->delta_ticks_from_prev;
while (t != timeout) {
t = (struct _timeout *)sys_dlist_peek_next(&_timeout_q,
&t->node);
remaining_ticks += t->delta_ticks_from_prev;
}
}
irq_unlock(key);
return _ticks_to_ms(remaining_ticks);
}
int32_t nano_timer_ticks_remain(struct nano_timer *timer)
{
int key = irq_lock();
int32_t remaining_ticks;
struct _nano_timeout *t = &timer->timeout_data;
sys_dlist_t *timeout_q = &_nanokernel.timeout_q;
struct _nano_timeout *iterator;
if (t->delta_ticks_from_prev == -1) {
remaining_ticks = 0;
} else {
/*
* As nanokernel timeouts are stored in a linked list with
* delta_ticks_from_prev, to get the actual number of ticks
* remaining for the timer, walk through the timeouts list
* and accumulate all the delta_ticks_from_prev values up to
* the timer.
*/
iterator =
(struct _nano_timeout *)sys_dlist_peek_head(timeout_q);
remaining_ticks = iterator->delta_ticks_from_prev;
while (iterator != t) {
iterator = (struct _nano_timeout *)sys_dlist_peek_next(
timeout_q, &iterator->node);
remaining_ticks += iterator->delta_ticks_from_prev;
}
}
irq_unlock(key);
return remaining_ticks;
}
/**
* @brief Prepare a working set of readers/writers
*
* Prepare a list of "working threads" into/from which the data
* will be directly copied. This list is useful as it is used to ...
*
* 1. avoid double copying
* 2. minimize interrupt latency as interrupts are unlocked
* while copying data
* 3. ensure a timeout can not make the request impossible to satisfy
*
* The list is populated with previously pended threads that will be ready to
* run after the pipe call is complete.
*
* Important things to remember when reading from the pipe ...
* 1. If there are writers int @a wait_q, then the pipe's buffer is full.
* 2. Conversely if the pipe's buffer is not full, there are no writers.
* 3. The amount of available data in the pipe is the sum the bytes used in
* the pipe (@a pipe_space) and all the requests from the waiting writers.
* 4. Since data is read from the pipe's buffer first, the working set must
* include writers that will (try to) re-fill the pipe's buffer afterwards.
*
* Important things to remember when writing to the pipe ...
* 1. If there are readers in @a wait_q, then the pipe's buffer is empty.
* 2. Conversely if the pipe's buffer is not empty, then there are no readers.
* 3. The amount of space available in the pipe is the sum of the bytes unused
* in the pipe (@a pipe_space) and all the requests from the waiting readers.
*
* @return false if request is unsatisfiable, otherwise true
*/
static bool _pipe_xfer_prepare(sys_dlist_t *xfer_list,
struct k_thread **waiter,
_wait_q_t *wait_q,
size_t pipe_space,
size_t bytes_to_xfer,
size_t min_xfer,
s32_t timeout)
{
sys_dnode_t *node;
struct k_thread *thread;
struct k_pipe_desc *desc;
size_t num_bytes = 0;
if (timeout == K_NO_WAIT) {
for (node = sys_dlist_peek_head(wait_q); node != NULL;
node = sys_dlist_peek_next(wait_q, node)) {
thread = (struct k_thread *)node;
desc = (struct k_pipe_desc *)thread->base.swap_data;
num_bytes += desc->bytes_to_xfer;
if (num_bytes >= bytes_to_xfer) {
break;
}
}
if (num_bytes + pipe_space < min_xfer) {
return false;
}
}
/*
* Either @a timeout is not K_NO_WAIT (so the thread may pend) or
* the entire request can be satisfied. Generate the working list.
*/
sys_dlist_init(xfer_list);
num_bytes = 0;
while ((thread = (struct k_thread *) sys_dlist_peek_head(wait_q))) {
desc = (struct k_pipe_desc *)thread->base.swap_data;
num_bytes += desc->bytes_to_xfer;
if (num_bytes > bytes_to_xfer) {
/*
* This request can not be fully satisfied.
* Do not remove it from the wait_q.
* Do not abort its timeout (if applicable).
* Do not add it to the transfer list
*/
break;
}
/*
* This request can be fully satisfied.
* Remove it from the wait_q.
* Abort its timeout.
* Add it to the transfer list.
*/
_unpend_thread(thread);
_abort_thread_timeout(thread);
sys_dlist_append(xfer_list, &thread->base.k_q_node);
}
*waiter = (num_bytes > bytes_to_xfer) ? thread : NULL;
return true;
}
