LTOBD2Adapter: Race Condition in Command Queue Access about ltsupportautomotive HOT 7 OPEN

Thanks for this report. The actual problem looks like a multithreading race condition – I should check whether access of the command queue is a) coordinated or b) make the command queue thread-safe.

That said, if you're checking values in a loop, you have to take care that you're not adding commands faster than they are handled, so instead of adding based on a timer it would be better to use the completion handler to schedule the next iteration.

Last but not least, there are several optimizations that I want to tackle in 2019, namely adding facilities to group multiple PID queries (in order to save bandwidth), and also something to ease repeating queries.

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Tested this in debug and _commandQueue is between 1 and 6 after adding commands.
i dont know why it can go up to 7000.
And why it is possible to get this Error: index beyond bounds

i will try it with this solution:

if ( [_commandQueue count] > 200 )
{
    NSLog( @"cancelPendingCommands : Has more than 200" );
    [self cancelPendingCommands];
}

after: asyncProcessCommandQueue

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created an outlet for the queue count and slow down the new requests if needed.
for me its currently ok.
Thank you for detailed answer 👍

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Have you any idea how to fix this ?
Yesterday it was 0...4 [index 6 beyond bounds]

I start the "transmitMultipleCommands" function in the main queue but it doesn´t help.

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This Error only happens all >50.000 readings so its hard to find the error but i think this might be help.

-(void)asyncEnqueueInternalCommand:(LTOBD2AdapterInternalCommand*)internalCommand
{
    @synchronized(self) {
        [_commandQueue addObject:internalCommand];
        [self asyncProcessCommandQueue];
    }
}

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@synchronized(self) is not the solution.
Now i test with the serial dispatchqueue.

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created pull request for the solution. #26

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