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FreeRTOS / FreeRTOS-Cellular-Interface

FreeRTOS Cellular Interface implementation of the 3GPP TS v27.007 standard.
MIT License
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[BUG] Sara R4 socket opening race condition #91

Closed es-kaga closed 2 years ago

es-kaga commented 2 years ago

Hi. I am using Sara R4 module with the FreeRTOS library I noticed that when I am opening the socket using Cellular_SocketConnect then I got URC callback registered by the Cellular_SocketRegisterSocketOpenCallback before exiting Cellular_SocketConnect which leads to race condition on the socket state socketHandle->socketState since it is set to SOCKETSTATE_CONNECTING despite the fact that socket is already connected. I am not able to send any data on the socket because send function has a check against socket state.

I checked that it happens when cellular module return URC(+UUSOCO: 0,0) just right after response to the AT+USOCO= and the calling thread has lower priorioty then the cellular library receive thread then the URC handler is executed before exiting Cellular_SocketConnect and socket state is invalid.

The temporary workaround seems to be increasing the priority of thread calling Cellular_SocketConnect and setting it back after this function execution.

Could you take a look into this issue ?

chinglee-iot commented 2 years ago

@es-kaga Thank you for your feedback. We will look into this problem and reply later.

chinglee-iot commented 2 years ago

@es-kaga I reproduced the problem you described by adding delay before this line.

Socket connected URC should only be received after successfully sending the AT command to modem. PR #92 move the line to set CONNECTING state before sending the AT command. The state is reverted if the AT command failed.

Once this PR is merged. I will update the issue again.

chinglee-iot commented 2 years ago

The PR is merged. Thank you for your feedback. If there is further question related to this issue, please reopen this issue.