mod_audio_fork - need of multiple locks/mutexes

[anshumanr]

Hi @davehorton
We are using mod_audio_fork module. I was going through the code and could not understand the need to acquire/lock multiple mutexes in func fork_frame()

1. mutex part of variable type struct private_data is acquired at lws_glue.cpp#L530.
2. mutex part of class AudioPipe and used to access the audio buffers is acquired at lws_glue.cpp#L541

Also, this callback is invoked from func switch_core_session_read_frame() in switch_core_io.c inside a lock (bug->read_mutex). So I could not understand the need to acquire multiple mutexes in fork_frame().
Could you please throw some pointers as to what I missed?
Thanks.

[davehorton]

please be patient as you are asking for a detailed investigation and description of the code. If possible I will get to this.

[anshumanr]

I seem to have found the missing piece of my understanding.

1. struct private_data is accessed in 2 different threads - fork_frame() and fork_session_cleanup(). I believe they can be invoked by FS in 2 different threads.
2. same for object of type AudioPipe. It is accessed in fork_frame() and in AudioPipe::lws_callback() for case LWS_CALLBACK_CLIENT_WRITEABLE. Need to check what that case means.