fix(iot-dev): Fix potential deadlock when closing while reconnecting #1393
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| @@ -452,28 +455,17 @@ void registerMultiplexingConnectionStateCallback(IotHubConnectionStatusChangeCal | |||
| @Override | |||
| public void execute(IotHubConnectionStatus status, IotHubConnectionStatusChangeReason statusChangeReason, Throwable throwable, Object callbackContext) | |||
| { | |||
| synchronized (this.stateLock) | |||
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This lock statement was the cause of the issue. The reconnection thread would first grab the reconnectionLock in IotHubTransport.java, then attempt to notify this DeviceIO layer that the transport is reconnecting, so it would need to grab this stateLock, too.
But if the user had initiated a close call already, then this lock was grabbed already by the user's thread. Once the user's thread has grabbed this stateLock, it then attempts to grab the reconnectionLock in IothubTransport.java.
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There is no need to synchronize on this lock in this callback since it is either called by the user's thread that called open/close (which already grabbed this lock in this deviceIO layer), or it is called by the reconnection thread. When it is called by the reconnection thread, we know that there isn't a close call happening since we have the reconnectionLock in the IotHubTransport layer preventing exactly that.
timtay-microsoft
requested review from
abhipsaMisra,
azabbasi,
drwill-ms and
jamdavi
as code owners
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/azp run |
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Azure Pipelines successfully started running 4 pipeline(s). |
If a user calls open/close while already closing/opening, the deviceIO layer will make the first call finish before running the second call.
If a user calls close while the client is reconnecting, the close call will notify the reconnection thread to stop, and will wait until reconnection has finished (failed or success) before closing the client.
If a user calls open while the client is reconnecting, the open call will return without doing anything because the SDK is still considered "open"
If a reconnection event happens while the user is closing, the reconnection event is ignored.
#1393