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/*
* Copyright (c) 2008-2014 Travis Geiselbrecht
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files
* (the "Software"), to deal in the Software without restriction,
* including without limitation the rights to use, copy, modify, merge,
* publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
/**
* @file
* @brief Event wait and signal functions for threads.
* @defgroup event Events
*
* An event is a subclass of a wait queue.
*
* Threads wait for events, with optional timeouts.
*
* Events are "signaled", releasing waiting threads to continue.
* Signals may be one-shot signals (EVENT_FLAG_AUTOUNSIGNAL), in which
* case one signal releases only one thread, at which point it is
* automatically cleared. Otherwise, signals release all waiting threads
* to continue immediately until the signal is manually cleared with
* event_unsignal().
*
* @{
*/
#include <kernel/event.h>
#include <debug.h>
#include <assert.h>
#include <err.h>
#include <kernel/thread.h>
/**
* @brief Initialize an event object
*
* @param e Event object to initialize
* @param initial Initial value for "signaled" state
* @param flags 0 or EVENT_FLAG_AUTOUNSIGNAL
*/
void event_init(event_t *e, bool initial, uint flags)
{
*e = (event_t)EVENT_INITIAL_VALUE(*e, initial, flags);
}
/**
* @brief Destroy an event object.
*
* Event's resources are freed and it may no longer be
* used until event_init() is called again. Any threads
* still waiting on the event will be resumed.
*
* @param e Event object to initialize
*/
void event_destroy(event_t *e)
{
DEBUG_ASSERT(e->magic == EVENT_MAGIC);
THREAD_LOCK(state);
e->magic = 0;
e->signaled = false;
e->flags = 0;
wait_queue_destroy(&e->wait, true);
THREAD_UNLOCK(state);
}
/**
* @brief Wait for event to be signaled
*
* If the event has already been signaled, this function
* returns immediately. Otherwise, the current thread
* goes to sleep until the event object is signaled,
* the timeout is reached, or the event object is destroyed
* by another thread.
*
* @param e Event object
* @param timeout Timeout value, in ms
*
* @return 0 on success, ERR_TIMED_OUT on timeout,
* other values on other errors.
*/
status_t event_wait_timeout(event_t *e, lk_time_t timeout)
{
status_t ret = NO_ERROR;
DEBUG_ASSERT(e->magic == EVENT_MAGIC);
THREAD_LOCK(state);
if (e->signaled) {
/* signaled, we're going to fall through */
if (e->flags & EVENT_FLAG_AUTOUNSIGNAL) {
/* autounsignal flag lets one thread fall through before unsignaling */
e->signaled = false;
}
} else {
/* unsignaled, block here */
ret = wait_queue_block(&e->wait, timeout);
}
THREAD_UNLOCK(state);
return ret;
}
/**
* @brief Signal an event
*
* Signals an event. If EVENT_FLAG_AUTOUNSIGNAL is set in the event
* object's flags, only one waiting thread is allowed to proceed. Otherwise,
* all waiting threads are allowed to proceed until such time as
* event_unsignal() is called.
*
* @param e Event object
* @param reschedule If true, waiting thread(s) are executed immediately,
* and the current thread resumes only after the
* waiting threads have been satisfied. If false,
* waiting threads are placed at the end of the run
* queue.
*
* @return Returns NO_ERROR on success.
*/
status_t event_signal(event_t *e, bool reschedule)
{
DEBUG_ASSERT(e->magic == EVENT_MAGIC);
THREAD_LOCK(state);
if (!e->signaled) {
if (e->flags & EVENT_FLAG_AUTOUNSIGNAL) {
/* try to release one thread and leave unsignaled if successful */
if (wait_queue_wake_one(&e->wait, reschedule, NO_ERROR) <= 0) {
/*
* if we didn't actually find a thread to wake up, go to
* signaled state and let the next call to event_wait
* unsignal the event.
*/
e->signaled = true;
}
} else {
/* release all threads and remain signaled */
e->signaled = true;
wait_queue_wake_all(&e->wait, reschedule, NO_ERROR);
}
}
THREAD_UNLOCK(state);
return NO_ERROR;
}
/**
* @brief Clear the "signaled" property of an event
*
* Used mainly for event objects without the EVENT_FLAG_AUTOUNSIGNAL
* flag. Once this function is called, threads that call event_wait()
* functions will once again need to wait until the event object
* is signaled.
*
* @param e Event object
*
* @return Returns NO_ERROR on success.
*/
status_t event_unsignal(event_t *e)
{
DEBUG_ASSERT(e->magic == EVENT_MAGIC);
e->signaled = false;
return NO_ERROR;
}
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