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Collaboration diagram for Event Management:
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Threads may wait for events from other threads or interrupts or may post or broadcast events to other threads.
Waiting threads line up in priority ordered queues, so more than one thread may wait for the same event. A waiting queue is a simple linked list of waiting threads.
Events are posted to a waiting queue, moving the thread from waiting (sleeping) state to ready-to-run state. A running thread may also broadcast an event to a specified queue, waking up all threads on that queue.
Usually a woken up thread takes over the CPU, if it's priority is equal or higher than the currently running thread. However, events can be posted asynchronously, in which case the posting thread continues to run.
Interrupt can also post events, but have to use the specific function NutEventPostFromIrq().
Defines | |
| #define | SIGNALED ((void *)-1) |
| Signaled state definition. | |
| #define | NUT_WAIT_INFINITE 0 |
| Infinite waiting time definition. | |
| #define | NutEventPostFromIrq(qp) |
| Post an event to a specified queue from interrupt context. | |
Functions | |
| void | NutEventTimeout (HANDLE timer, void *arg) |
| Timer callback in case of event timeout. | |
| int | NutEventWait (volatile HANDLE *qhp, u_long ms) |
| Wait for an event in a specified queue. | |
| int | NutEventWaitNext (volatile HANDLE *qhp, u_long ms) |
| Wait for a new event in a specified queue. | |
| int | NutEventPostAsync (volatile HANDLE *qhp) |
| Asynchronously post an event to a specified queue. | |
| int | NutEventPost (volatile HANDLE *qhp) |
| Post an event to a specified queue. | |
| int | NutEventBroadcastAsync (volatile HANDLE *qhp) |
| Asynchronously broadcast an event to a specified queue. | |
| int | NutEventBroadcast (volatile HANDLE *qhp) |
| Broadcast an event to a specified queue. | |
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Signaled state definition. The root of an event queue is set to this value if an event is posted to an empty queue. As this may happen during interrupts, the root of an event queue must be considered volatile. Timer handles in the THREADINFO structure are set to this value if a timeout occured while waiting for an event. |
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Infinite waiting time definition. Applications should use this value to disable timeout monitoring while waiting for an event. |
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Value: { \
if (*qp == 0) { \
*qp = SIGNALED; \
} \
else if (*qp != SIGNALED) { \
NUTTHREADINFO *tp = (NUTTHREADINFO *)(*qp); \
tp->td_qpec++; \
} \
}
Wake up the thread with the highest priority waiting on the specified queue. This function is explicitly provided for IRQ handlers to wakeup waiting user threads. Internally a counter is used to keep track of the posted events. This counter will be examined when the currently running thread is ready to release the CPU.
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Timer callback in case of event timeout. Applications should not call this function. It is provided as a global to enable debugging code inspecting the callbacks in the timer list.
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Wait for an event in a specified queue. Give up the CPU until another thread or an interrupt routine posts an event to this queue or until a time-out occurs, whichever comes first. If previously an event had been posted to this queue without any thread waiting, then the thread will not wait for a new event, but may still pass CPU control, if another thread with equal or higher priority is ready to run.
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Wait for a new event in a specified queue. Give up the CPU until another thread or an interrupt routine posts an event to this queue or until a time-out occurs, whichever comes first. This call is similar to NutEventWait(), but will ignore the SIGNALED state of the queue. This way, previously posted events to an empty queue are not considered.
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Asynchronously post an event to a specified queue. Wake up the thread with the highest priority waiting on the specified queue. But even if the priority of the woken thread is higher than the current thread's priority, the current one continues running. If no thread is waiting, then the queue will be set to the SIGNALED state.
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Post an event to a specified queue. Wake up the thread with the highest priority waiting on this queue. If the priority of the waiting thread is higher or equal than the current thread's priority, then the current thread is stopped and CPU control is passed to the waiting thread. If no thread is waiting, the queue will be set to the signaled state.
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Asynchronously broadcast an event to a specified queue. Wake up all threads waiting on this queue. But even if the priority of any woken thread is higher than the current thread's priority, the current one continues running. In opposite to NutEventPostAsync(), the queue will be cleared in any case, even if it is in signaled state. Applications may use this call to make sure, that a queue is cleared before initiating some event triggering action.
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Broadcast an event to a specified queue. Wake up all threads waiting on this queue. If the priority of any waiting thread is higher or equal than the current thread's priority, then the current thread is stopped and CPU control is passed to the woken up thread with the highest priority. In opposite to NutEventPost(), the queue will be cleared in any case, even if it is in signaled state. Applications may use this call to make sure, that a queue is cleared before initiating some event triggering action.
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