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Change HAL notifier to polling. (#627)

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This moves the thread code to the WPILib layer, fixing various potential
races and significantly simplifying the HAL implementation.
This commit is contained in:
Peter Johnson
2017-11-19 17:58:40 -08:00
committed by GitHub
parent 4a07f0380f
commit d214b36786
12 changed files with 461 additions and 587 deletions
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79
wpilibc/src/main/native/cpp/Notifier.cpp
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@@ -15,8 +15,6 @@
using namespace frc;
wpi::mutex Notifier::m_destructorMutex;
/**
* Create a Notifier for timer event notification.
*
@@ -28,8 +26,31 @@ Notifier::Notifier(TimerEventHandler handler) {
wpi_setWPIErrorWithContext(NullParameter, "handler must not be nullptr");
m_handler = handler;
int32_t status = 0;
m_notifier = HAL_InitializeNotifier(&Notifier::Notify, this, &status);
m_notifier = HAL_InitializeNotifier(&status);
wpi_setErrorWithContext(status, HAL_GetErrorMessage(status));
m_thread = std::thread([=] {
for (;;) {
int32_t status = 0;
HAL_NotifierHandle notifier = m_notifier.load();
if (notifier == 0) break;
uint64_t curTime = HAL_WaitForNotifierAlarm(notifier, &status);
if (curTime == 0 || status != 0) break;
TimerEventHandler handler;
{
std::lock_guard<wpi::mutex> sync(m_processMutex);
handler = m_handler;
if (m_periodic) {
m_expirationTime += m_period;
UpdateAlarm();
}
}
// call callback
if (handler) handler();
}
});
}
/**
@@ -39,14 +60,13 @@ Notifier::~Notifier() {
int32_t status = 0;
// atomically set handle to 0, then clean
HAL_NotifierHandle handle = m_notifier.exchange(0);
HAL_CleanNotifier(handle, &status);
HAL_StopNotifier(handle, &status);
wpi_setErrorWithContext(status, HAL_GetErrorMessage(status));
/* Acquire the mutex; this makes certain that the handler is not being
* executed by the interrupt manager.
*/
std::lock_guard<wpi::mutex> lockStatic(Notifier::m_destructorMutex);
std::lock_guard<wpi::mutex> lock(m_processMutex);
// Join the thread to ensure the handler has exited.
if (m_thread.joinable()) m_thread.join();
HAL_CleanNotifier(handle, &status);
}
/**
@@ -55,37 +75,21 @@ Notifier::~Notifier() {
void Notifier::UpdateAlarm() {
int32_t status = 0;
// Return if we are being destructed, or were not created successfully
if (m_notifier == 0) return;
auto notifier = m_notifier.load();
if (notifier == 0) return;
HAL_UpdateNotifierAlarm(
m_notifier, static_cast<uint64_t>(m_expirationTime * 1e6), &status);
notifier, static_cast<uint64_t>(m_expirationTime * 1e6), &status);
wpi_setErrorWithContext(status, HAL_GetErrorMessage(status));
}
/**
* Notify is called by the HAL layer. We simply need to pass it through to
* the user handler.
* Change the handler function.
*
* @param handler Handler
*/
void Notifier::Notify(uint64_t currentTimeInt, HAL_NotifierHandle handle) {
Notifier* notifier;
{
// Lock static mutex to grab the notifier param
std::lock_guard<wpi::mutex> lock(Notifier::m_destructorMutex);
int32_t status = 0;
auto notifierPointer = HAL_GetNotifierParam(handle, &status);
if (notifierPointer == nullptr) return;
notifier = static_cast<Notifier*>(notifierPointer);
notifier->m_processMutex.lock();
}
if (notifier->m_periodic) {
notifier->m_expirationTime += notifier->m_period;
notifier->UpdateAlarm();
}
auto handler = notifier->m_handler;
if (handler) handler();
notifier->m_processMutex.unlock();
void Notifier::SetHandler(TimerEventHandler handler) {
std::lock_guard<wpi::mutex> sync(m_processMutex);
m_handler = handler;
}
/**
@@ -132,11 +136,6 @@ void Notifier::StartPeriodic(double period) {
*/
void Notifier::Stop() {
int32_t status = 0;
HAL_StopNotifierAlarm(m_notifier, &status);
HAL_CancelNotifierAlarm(m_notifier, &status);
wpi_setErrorWithContext(status, HAL_GetErrorMessage(status));
// Wait for a currently executing handler to complete before returning from
// Stop()
std::lock_guard<wpi::mutex> lockStatic(Notifier::m_destructorMutex);
std::lock_guard<wpi::mutex> lock(m_processMutex);
}