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[hal, wpilib] New DS thread model and implementation (#3787)

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The current DS thread model has some pretty major issues. It makes it difficult to know if all data is from the same remote packet, and if the data changes while the robot loop is running. Additionally, the DS thread is used for a few other things (MotorSafety and State Tracking for EducationalRobot). This also makes sim difficult, as user code has to wait for the thread to know it has new data.

This change completely rethinks how threading works in the driver station model.

First, the DS HAL system receives a new data callback, either from Netcomm or DriverStationSim. Inside the context of this callback, all the low latency data is read and put into a cache. Doing some investigation on the robot side, this is perfectly safe to do, and also ensures a ds packet will not be parsed before we finish reading the current packet data.

After all data is read, the cache is swapped with a 2nd buffer. This buffer just stores the data, none of the HAL DS calls read from this buffer. An event is then fired, stating there is new data ready to go.

Robot code calls HAL_UpdateDSData(). This swaps the 2nd buffer with a 3rd buffer, which always contains the current data. This data will not be updated until HAL_UpdateDSData is called again. Which solves the state problem.

The high level driver station classes have. an updateData() call, which calls HAL_UpdateDSData, and then update button state variables, then data log and update the NT FMS data table (Java also caches across the JNI boundary here, but that could trivially be removed). An extra event provider is provided, allowing other threads to know when this call has been completed.

IterativeRobotBase calls DS.updateData() at the beginning of each loop, and only once per loop. This means all commands will always have the same state.

All of this means there is no longer a DS thread. Everything happens synchronously. This means Sim and testing is easier, as you can just call DriverStationSim.NotifyNewData(), and then DriverStation.UpdateData(), and you can guarantee that all the DriverStation.*** data is up to date.

As for Motor Safety and Educational Robot State Handling, those can all be handled by their own threads. The Educational Thread only needs to run under EducationalRobot, and MotorSafety will only be started if there is a motor safety object enabled.
This commit is contained in:
Thad House
2022-10-21 22:01:55 -07:00
committed by GitHub
parent c195b4fc46
commit 4a401b89d7
53 changed files with 1649 additions and 1384 deletions
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235
hal/src/main/native/sim/DriverStation.cpp
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@@ -14,32 +14,78 @@
#include <string>
#include <fmt/format.h>
#include <wpi/EventVector.h>
#include <wpi/condition_variable.h>
#include <wpi/mutex.h>
#include "HALInitializer.h"
#include "hal/Errors.h"
#include "hal/cpp/fpga_clock.h"
#include "hal/simulation/MockHooks.h"
#include "mockdata/DriverStationDataInternal.h"
static wpi::mutex msgMutex;
static wpi::condition_variable* newDSDataAvailableCond;
static wpi::mutex newDSDataAvailableMutex;
static int newDSDataAvailableCounter{0};
static std::atomic_bool isFinalized{false};
static std::atomic<HALSIM_SendErrorHandler> sendErrorHandler{nullptr};
static std::atomic<HALSIM_SendConsoleLineHandler> sendConsoleLineHandler{
nullptr};
using namespace hal;
static constexpr int kJoystickPorts = 6;
namespace {
struct JoystickDataCache {
JoystickDataCache() { std::memset(this, 0, sizeof(*this)); }
void Update();
HAL_JoystickAxes axes[kJoystickPorts];
HAL_JoystickPOVs povs[kJoystickPorts];
HAL_JoystickButtons buttons[kJoystickPorts];
HAL_AllianceStationID allianceStation;
double matchTime;
bool updated;
};
static_assert(std::is_standard_layout_v<JoystickDataCache>);
// static_assert(std::is_trivial_v<JoystickDataCache>);
static std::atomic_bool gShutdown{false};
struct FRCDriverStation {
~FRCDriverStation() { gShutdown = true; }
wpi::EventVector newDataEvents;
wpi::mutex cacheMutex;
};
} // namespace
void JoystickDataCache::Update() {
for (int i = 0; i < kJoystickPorts; i++) {
SimDriverStationData->GetJoystickAxes(i, &axes[i]);
SimDriverStationData->GetJoystickPOVs(i, &povs[i]);
SimDriverStationData->GetJoystickButtons(i, &buttons[i]);
}
allianceStation = SimDriverStationData->allianceStationId;
matchTime = SimDriverStationData->matchTime;
}
#define CHECK_JOYSTICK_NUMBER(stickNum) \
if ((stickNum) < 0 || (stickNum) >= HAL_kMaxJoysticks) \
return PARAMETER_OUT_OF_RANGE
static HAL_ControlWord newestControlWord;
static JoystickDataCache caches[3];
static JoystickDataCache* currentRead = &caches[0];
static JoystickDataCache* currentCache = &caches[1];
static JoystickDataCache* cacheToUpdate = &caches[2];
static ::FRCDriverStation* driverStation;
namespace hal::init {
void InitializeDriverStation() {
static wpi::condition_variable nddaC;
newDSDataAvailableCond = &nddaC;
static FRCDriverStation ds;
driverStation = &ds;
}
} // namespace hal::init
using namespace hal;
extern "C" {
void HALSIM_SetSendError(HALSIM_SendErrorHandler handler) {
@@ -122,39 +168,49 @@ int32_t HAL_SendConsoleLine(const char* line) {
}
int32_t HAL_GetControlWord(HAL_ControlWord* controlWord) {
std::memset(controlWord, 0, sizeof(HAL_ControlWord));
controlWord->enabled = SimDriverStationData->enabled;
controlWord->autonomous = SimDriverStationData->autonomous;
controlWord->test = SimDriverStationData->test;
controlWord->eStop = SimDriverStationData->eStop;
controlWord->fmsAttached = SimDriverStationData->fmsAttached;
controlWord->dsAttached = SimDriverStationData->dsAttached;
std::scoped_lock lock{driverStation->cacheMutex};
*controlWord = newestControlWord;
return 0;
}
HAL_AllianceStationID HAL_GetAllianceStation(int32_t* status) {
*status = 0;
return SimDriverStationData->allianceStationId;
std::scoped_lock lock{driverStation->cacheMutex};
return currentRead->allianceStation;
}
int32_t HAL_GetJoystickAxes(int32_t joystickNum, HAL_JoystickAxes* axes) {
SimDriverStationData->GetJoystickAxes(joystickNum, axes);
CHECK_JOYSTICK_NUMBER(joystickNum);
std::scoped_lock lock{driverStation->cacheMutex};
*axes = currentRead->axes[joystickNum];
return 0;
}
int32_t HAL_GetJoystickPOVs(int32_t joystickNum, HAL_JoystickPOVs* povs) {
SimDriverStationData->GetJoystickPOVs(joystickNum, povs);
CHECK_JOYSTICK_NUMBER(joystickNum);
std::scoped_lock lock{driverStation->cacheMutex};
*povs = currentRead->povs[joystickNum];
return 0;
}
int32_t HAL_GetJoystickButtons(int32_t joystickNum,
HAL_JoystickButtons* buttons) {
SimDriverStationData->GetJoystickButtons(joystickNum, buttons);
CHECK_JOYSTICK_NUMBER(joystickNum);
std::scoped_lock lock{driverStation->cacheMutex};
*buttons = currentRead->buttons[joystickNum];
return 0;
}
void HAL_GetAllJoystickData(HAL_JoystickAxes* axes, HAL_JoystickPOVs* povs,
HAL_JoystickButtons* buttons) {
std::scoped_lock lock{driverStation->cacheMutex};
std::memcpy(axes, currentRead->axes, sizeof(currentRead->axes));
std::memcpy(povs, currentRead->povs, sizeof(currentRead->povs));
std::memcpy(buttons, currentRead->buttons, sizeof(currentRead->buttons));
}
int32_t HAL_GetJoystickDescriptor(int32_t joystickNum,
HAL_JoystickDescriptor* desc) {
CHECK_JOYSTICK_NUMBER(joystickNum);
SimDriverStationData->GetJoystickDescriptor(joystickNum, desc);
return 0;
}
@@ -196,7 +252,8 @@ int32_t HAL_SetJoystickOutputs(int32_t joystickNum, int64_t outputs,
}
double HAL_GetMatchTime(int32_t* status) {
return SimDriverStationData->matchTime;
std::scoped_lock lock{driverStation->cacheMutex};
return currentRead->matchTime;
}
int32_t HAL_GetMatchInfo(HAL_MatchInfo* info) {
@@ -224,103 +281,57 @@ void HAL_ObserveUserProgramTest(void) {
// TODO
}
static int& GetThreadLocalLastCount() {
// There is a rollover error condition here. At Packet# = n * (uintmax), this
// will return false when instead it should return true. However, this at a
// 20ms rate occurs once every 2.7 years of DS connected runtime, so not
// worth the cycles to check.
thread_local int lastCount{0};
return lastCount;
void HAL_RefreshDSData(void) {
HAL_ControlWord controlWord;
std::memset(&controlWord, 0, sizeof(controlWord));
controlWord.enabled = SimDriverStationData->enabled;
controlWord.autonomous = SimDriverStationData->autonomous;
controlWord.test = SimDriverStationData->test;
controlWord.eStop = SimDriverStationData->eStop;
controlWord.fmsAttached = SimDriverStationData->fmsAttached;
controlWord.dsAttached = SimDriverStationData->dsAttached;
std::scoped_lock lock{driverStation->cacheMutex};
if (currentCache->updated) {
std::swap(currentCache, currentRead);
currentCache->updated = false;
}
newestControlWord = controlWord;
}
HAL_Bool HAL_IsNewControlData(void) {
std::scoped_lock lock(newDSDataAvailableMutex);
int& lastCount = GetThreadLocalLastCount();
int currentCount = newDSDataAvailableCounter;
if (lastCount == currentCount) {
return false;
}
lastCount = currentCount;
return true;
}
void HAL_WaitForDSData(void) {
HAL_WaitForDSDataTimeout(0);
}
HAL_Bool HAL_WaitForDSDataTimeout(double timeout) {
std::unique_lock lock(newDSDataAvailableMutex);
int& lastCount = GetThreadLocalLastCount();
int currentCount = newDSDataAvailableCounter;
if (lastCount != currentCount) {
lastCount = currentCount;
return true;
}
if (isFinalized.load()) {
return false;
}
auto timeoutTime =
std::chrono::steady_clock::now() + std::chrono::duration<double>(timeout);
while (newDSDataAvailableCounter == currentCount) {
if (timeout > 0) {
auto timedOut = newDSDataAvailableCond->wait_until(lock, timeoutTime);
if (timedOut == std::cv_status::timeout) {
return false;
}
} else {
newDSDataAvailableCond->wait(lock);
}
}
lastCount = newDSDataAvailableCounter;
return true;
}
// Constant number to be used for our occur handle
constexpr int32_t refNumber = 42;
static int32_t newDataOccur(uint32_t refNum) {
// Since we could get other values, require our specific handle
// to signal our threads
if (refNum != refNumber) {
return 0;
}
SimDriverStationData->CallNewDataCallbacks();
std::scoped_lock lock(newDSDataAvailableMutex);
// Nofify all threads
newDSDataAvailableCounter++;
newDSDataAvailableCond->notify_all();
return 0;
}
void HAL_InitializeDriverStation(void) {
hal::init::CheckInit();
static std::atomic_bool initialized{false};
static wpi::mutex initializeMutex;
// Initial check, as if it's true initialization has finished
if (initialized) {
void HAL_ProvideNewDataEventHandle(WPI_EventHandle handle) {
if (gShutdown) {
return;
}
std::scoped_lock lock(initializeMutex);
// Second check in case another thread was waiting
if (initialized) {
return;
}
SimDriverStationData->ResetData();
std::atexit([]() {
isFinalized.store(true);
HAL_ReleaseDSMutex();
});
initialized = true;
driverStation->newDataEvents.Add(handle);
}
void HAL_ReleaseDSMutex(void) {
newDataOccur(refNumber);
void HAL_RemoveNewDataEventHandle(WPI_EventHandle handle) {
if (gShutdown) {
return;
}
driverStation->newDataEvents.Remove(handle);
}
HAL_Bool HAL_GetOutputsEnabled(void) {
std::scoped_lock lock{driverStation->cacheMutex};
return newestControlWord.enabled && newestControlWord.dsAttached;
}
} // extern "C"
namespace hal {
void NewDriverStationData() {
cacheToUpdate->Update();
{
std::scoped_lock lock{driverStation->cacheMutex};
std::swap(currentCache, cacheToUpdate);
currentCache->updated = true;
}
driverStation->newDataEvents.Wakeup();
SimDriverStationData->CallNewDataCallbacks();
}
void InitializeDriverStation() {
SimDriverStationData->ResetData();
}
} // namespace hal