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Issue created by Administrator@rootContributor0 of 6 checklist items completed0/6 checklist items

container.close() holds GIL, causing deadlock when combined with pipe

Created by: ninja-

Overview

I have a PyAV stream that writes to output that is a unix pipe (mkfifo). When calling container.close(), libav waits for the other side to finish reading data written to pipe - as it should. Unfortunately, since the pipe consumer is another Python thread, that leads to deadlock during close(), as that thread can never read the last bits of data as container.close() holds the GIL.

The workaround I used is to push PyAV to "multiprocessing" process...

Expected behavior

There should be no GIL hold during calls to demux() or container.close()

Actual behavior

GIL is hold for container.close()

Build report:

Investigation

{{ What you did to isolate the problem. }}

Reproduction

Create a mkfifo file. Create two threads, one reads from the pipe, and other writes to it using PyAV container, and later does PyAV.close() See high chance of GIL deadlock during close()

Versions

  • OS: Linux
  • PyAV runtime: pip3 latest
  • PyAV build:
  • FFmpeg:

Research

I have done the following:

Additional context