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https://github.com/wpilibsuite/allwpilib
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e3191b0bfd
For the previous couple of months, the PID tests have been hanging. The reason that the tests have been hanging lies with the Notifier, not the PID controller. Basically, a deadlock was occuring during Notifier destruction when the notifier destructor was called while the notifier interrupt handler was being called. Because the low-level interrupt manager waits for the interrupt handler to finish executing before disabling itself, the notifier destructor would not exit until the ProcessQueue function finished. However, at the same time, the handler was attempting to lock the queueMutex before continuing; the Notifier destructor had locked the queueMutex while wrapping things up, meaning that the last run of the handler would not complete until the destructor did, resulting in a deadlock. In order to repair this, I reduced the scope of the lock on the queueMutex in the destructor so that it only locks when absolutely necessary. This should work now. This bug was likely introduced over the summer when we updated to stl mutexes and locks, which may have messed up the original lock structure. This likely did not affect any teams, as it can only occur if you are actively destroying every* Notifier object present and if the destructor happens to be called while the handler is being run. *Note: the component of the destructor causing issues only ran if the last Notifier object is being destroyed. Change-Id: I38ba4e60816a2a8d523e927c25378390a0755444
58 lines
2.1 KiB
C++
58 lines
2.1 KiB
C++
/*----------------------------------------------------------------------------*/
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/* Copyright (c) FIRST 2008. All Rights Reserved.
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*/
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/* Open Source Software - may be modified and shared by FRC teams. The code */
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/* must be accompanied by the FIRST BSD license file in $(WIND_BASE)/WPILib. */
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/*----------------------------------------------------------------------------*/
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#pragma once
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#include "ErrorBase.h"
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#include "HAL/cpp/priority_mutex.h"
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#include <thread>
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#include <atomic>
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typedef void (*TimerEventHandler)(void *param);
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class Notifier : public ErrorBase {
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public:
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Notifier(TimerEventHandler handler, void *param = nullptr);
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virtual ~Notifier();
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Notifier(const Notifier&) = delete;
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Notifier& operator=(const Notifier&) = delete;
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void StartSingle(double delay);
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void StartPeriodic(double period);
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void Stop();
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private:
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static Notifier *timerQueueHead;
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static priority_recursive_mutex queueMutex;
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static priority_mutex halMutex;
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static void *m_notifier;
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static std::atomic<int> refcount;
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static void ProcessQueue(
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uint32_t mask, void *params); // process the timer queue on a timer event
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static void
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UpdateAlarm(); // update the FPGA alarm since the queue has changed
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void InsertInQueue(
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bool reschedule); // insert this Notifier in the timer queue
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void DeleteFromQueue(); // delete this Notifier from the timer queue
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TimerEventHandler m_handler; // address of the handler
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void *m_param; // a parameter to pass to the handler
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double m_period = 0; // the relative time (either periodic or single)
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double m_expirationTime = 0; // absolute expiration time for the current event
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Notifier *m_nextEvent = nullptr; // next Nofifier event
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bool m_periodic = false; // true if this is a periodic event
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bool m_queued = false; // indicates if this entry is queued
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priority_mutex m_handlerMutex; // held by interrupt manager task while
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// handler call is in progress
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#ifdef FRC_SIMULATOR
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static std::thread m_task;
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static std::atomic<bool> m_stopped;
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#endif
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static void Run();
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};
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