zephyr/kernel/poll.c

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/*
* Copyright (c) 2017 Wind River Systems, Inc.
*
* SPDX-License-Identifier: Apache-2.0
*/
/**
* @file
*
* @brief Kernel asynchronous event polling interface.
*
* This polling mechanism allows waiting on multiple events concurrently,
* either events triggered directly, or from kernel objects or other kernel
* constructs.
*/
#include <kernel.h>
#include <kernel_structs.h>
#include <wait_q.h>
#include <ksched.h>
#include <misc/slist.h>
#include <misc/dlist.h>
#include <misc/__assert.h>
void k_poll_event_init(struct k_poll_event *event, u32_t type,
int mode, void *obj)
{
__ASSERT(mode == K_POLL_MODE_NOTIFY_ONLY,
"only NOTIFY_ONLY mode is supported\n");
__ASSERT(type < (1 << _POLL_NUM_TYPES), "invalid type\n");
__ASSERT(obj, "must provide an object\n");
event->poller = NULL;
/* event->tag is left uninitialized: the user will set it if needed */
event->type = type;
event->state = K_POLL_STATE_NOT_READY;
event->mode = mode;
event->unused = 0;
event->obj = obj;
}
/* must be called with interrupts locked */
static inline void set_polling_state(struct k_thread *thread)
{
_mark_thread_as_polling(thread);
}
/* must be called with interrupts locked */
static inline void clear_polling_state(struct k_thread *thread)
{
_mark_thread_as_not_polling(thread);
}
/* must be called with interrupts locked */
static inline int is_polling(void)
{
return _is_thread_polling(_current);
}
/* must be called with interrupts locked */
static inline int is_condition_met(struct k_poll_event *event, u32_t *state)
{
switch (event->type) {
case K_POLL_TYPE_SEM_AVAILABLE:
if (k_sem_count_get(event->sem) > 0) {
*state = K_POLL_STATE_SEM_AVAILABLE;
return 1;
}
break;
case K_POLL_TYPE_DATA_AVAILABLE:
if (!k_queue_is_empty(event->queue)) {
*state = K_POLL_STATE_FIFO_DATA_AVAILABLE;
return 1;
}
break;
case K_POLL_TYPE_SIGNAL:
if (event->signal->signaled) {
*state = K_POLL_STATE_SIGNALED;
return 1;
}
break;
case K_POLL_TYPE_IGNORE:
return 0;
default:
__ASSERT(0, "invalid event type (0x%x)\n", event->type);
break;
}
return 0;
}
static inline void add_event(sys_dlist_t *events, struct k_poll_event *event,
struct _poller *poller)
{
struct k_poll_event *pending;
pending = (struct k_poll_event *)sys_dlist_peek_tail(events);
if (!pending || _is_t1_higher_prio_than_t2(pending->poller->thread,
poller->thread)) {
sys_dlist_append(events, &event->_node);
return;
}
SYS_DLIST_FOR_EACH_CONTAINER(events, pending, _node) {
if (_is_t1_higher_prio_than_t2(poller->thread,
pending->poller->thread)) {
sys_dlist_insert_before(events, &pending->_node,
&event->_node);
return;
}
}
sys_dlist_append(events, &event->_node);
}
/* must be called with interrupts locked */
static inline int register_event(struct k_poll_event *event,
struct _poller *poller)
{
switch (event->type) {
case K_POLL_TYPE_SEM_AVAILABLE:
__ASSERT(event->sem, "invalid semaphore\n");
add_event(&event->sem->poll_events, event, poller);
break;
case K_POLL_TYPE_DATA_AVAILABLE:
__ASSERT(event->queue, "invalid queue\n");
add_event(&event->queue->poll_events, event, poller);
break;
case K_POLL_TYPE_SIGNAL:
__ASSERT(event->signal, "invalid poll signal\n");
add_event(&event->signal->poll_events, event, poller);
break;
case K_POLL_TYPE_IGNORE:
/* nothing to do */
break;
default:
__ASSERT(0, "invalid event type\n");
break;
}
event->poller = poller;
return 0;
}
/* must be called with interrupts locked */
static inline void clear_event_registration(struct k_poll_event *event)
{
event->poller = NULL;
switch (event->type) {
case K_POLL_TYPE_SEM_AVAILABLE:
__ASSERT(event->sem, "invalid semaphore\n");
sys_dlist_remove(&event->_node);
break;
case K_POLL_TYPE_DATA_AVAILABLE:
__ASSERT(event->queue, "invalid queue\n");
sys_dlist_remove(&event->_node);
break;
case K_POLL_TYPE_SIGNAL:
__ASSERT(event->signal, "invalid poll signal\n");
sys_dlist_remove(&event->_node);
break;
case K_POLL_TYPE_IGNORE:
/* nothing to do */
break;
default:
__ASSERT(0, "invalid event type\n");
break;
}
}
/* must be called with interrupts locked */
static inline void clear_event_registrations(struct k_poll_event *events,
int last_registered,
unsigned int key)
{
for (; last_registered >= 0; last_registered--) {
clear_event_registration(&events[last_registered]);
irq_unlock(key);
key = irq_lock();
}
}
static inline void set_event_ready(struct k_poll_event *event, u32_t state)
{
event->poller = NULL;
event->state |= state;
}
int k_poll(struct k_poll_event *events, int num_events, s32_t timeout)
{
__ASSERT(!_is_in_isr(), "");
__ASSERT(events, "NULL events\n");
__ASSERT(num_events > 0, "zero events\n");
int last_registered = -1, rc;
unsigned int key;
key = irq_lock();
set_polling_state(_current);
irq_unlock(key);
struct _poller poller = { .thread = _current };
/* find events whose condition is already fulfilled */
for (int ii = 0; ii < num_events; ii++) {
u32_t state;
key = irq_lock();
if (is_condition_met(&events[ii], &state)) {
set_event_ready(&events[ii], state);
clear_polling_state(_current);
} else if (timeout != K_NO_WAIT && is_polling()) {
rc = register_event(&events[ii], &poller);
if (rc == 0) {
++last_registered;
} else {
__ASSERT(0, "unexpected return code\n");
}
}
irq_unlock(key);
}
key = irq_lock();
/*
* If we're not polling anymore, it means that at least one event
* condition is met, either when looping through the events here or
* because one of the events registered has had its state changed.
*/
if (!is_polling()) {
clear_event_registrations(events, last_registered, key);
irq_unlock(key);
return 0;
}
clear_polling_state(_current);
if (timeout == K_NO_WAIT) {
irq_unlock(key);
return -EAGAIN;
}
_wait_q_t wait_q = _WAIT_Q_INIT(&wait_q);
_pend_current_thread(&wait_q, timeout);
int swap_rc = _Swap(key);
/*
* Clear all event registrations. If events happen while we're in this
* loop, and we already had one that triggered, that's OK: they will
* end up in the list of events that are ready; if we timed out, and
* events happen while we're in this loop, that is OK as well since
* we've already know the return code (-EAGAIN), and even if they are
* added to the list of events that occurred, the user has to check the
* return code first, which invalidates the whole list of event states.
*/
key = irq_lock();
clear_event_registrations(events, last_registered, key);
irq_unlock(key);
return swap_rc;
}
/* must be called with interrupts locked */
static int _signal_poll_event(struct k_poll_event *event, u32_t state,
int *must_reschedule)
{
*must_reschedule = 0;
if (!event->poller) {
goto ready_event;
}
struct k_thread *thread = event->poller->thread;
__ASSERT(event->poller->thread, "poller should have a thread\n");
clear_polling_state(thread);
if (!_is_thread_pending(thread)) {
goto ready_event;
}
if (_is_thread_timeout_expired(thread)) {
return -EAGAIN;
}
_unpend_thread(thread);
_abort_thread_timeout(thread);
_set_thread_return_value(thread,
state == K_POLL_STATE_NOT_READY ? -EINTR : 0);
if (!_is_thread_ready(thread)) {
goto ready_event;
}
_add_thread_to_ready_q(thread);
*must_reschedule = !_is_in_isr() && _must_switch_threads();
ready_event:
set_event_ready(event, state);
return 0;
}
/* returns 1 if a reschedule must take place, 0 otherwise */
int _handle_obj_poll_events(sys_dlist_t *events, u32_t state)
{
struct k_poll_event *poll_event;
int must_reschedule;
poll_event = (struct k_poll_event *)sys_dlist_get(events);
if (!poll_event) {
return 0;
}
(void)_signal_poll_event(poll_event, state, &must_reschedule);
return must_reschedule;
}
void k_poll_signal_init(struct k_poll_signal *signal)
{
sys_dlist_init(&signal->poll_events);
signal->signaled = 0;
/* signal->result is left unitialized */
}
int k_poll_signal(struct k_poll_signal *signal, int result)
{
unsigned int key = irq_lock();
struct k_poll_event *poll_event;
int must_reschedule;
signal->result = result;
signal->signaled = 1;
poll_event = (struct k_poll_event *)sys_dlist_get(&signal->poll_events);
if (!poll_event) {
irq_unlock(key);
return 0;
}
int rc = _signal_poll_event(poll_event, K_POLL_STATE_SIGNALED,
&must_reschedule);
if (must_reschedule) {
(void)_Swap(key);
} else {
irq_unlock(key);
}
return rc;
}