queue (and others) interrupt safe?

[vyruz1986]

Hi,

I am trying to use this library to have a FIFO buffer for ISR's. In the ISR I am calling the push() member function of a std::queue object like so:

struct STriggerRecord
{
   volatile int iSensorNumber;
   volatile int iSensorState;
   volatile unsigned long lTriggerTime;
};
std::queue<STriggerRecord> _STriggerQueue;
void RaceHandlerClass::TriggerSensor2()
{
   STriggerRecord S2Trigger;
   S2Trigger.lTriggerTime = micros();
   S2Trigger.iSensorNumber = 2;
   S2Trigger.iSensorState = digitalRead(_iS2Pin);;
   _STriggerQueue.push(S2Trigger);
}

However the last line of this code causes my arduino to freeze. After I posted this question on arduino.stackexchange, I got a comment from someone who implies the freeze is caused by 'malloc() not being reentrant, and since the.push()` member function of a queue tries to allocate memory, it causes the freeze.

Is there any way around this? I really need a FIFO buffer for my ISR's, and wouldn't know how to achieve this other than using an std::queue container (or similar).

[bobbyflowstate]

Did you figure this out? I'm trying to use a queue as well for me interrupt

[mike-matera]

Hi,

You can't use a queue this way in Arduino because you should never call malloc() in an ISR. Also, you can't use a mutex because an ISR should never block. Take a look at the documentation for Arduino's attachInterrupt():

https://www.arduino.cc/en/Reference/AttachInterrupt

That shows an ISR setting a variable declared 'volatile' and the main loop checking that variable. Your implementation must follow that pattern.