Remove `join_workers` from Pipeline destructor. (#53433)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53433
As described in https://github.com/pytorch/pytorch/issues/53413, the
pipeline destructor ends up hanging sometimes. The reason for this is that Pipe
uses daemon threads and as a result these threads could be destroyed before the
Pipe destructor is done. The Pipe destructor then calls `join_workers` which
waits on signals from the worker threads, which might be already dead and
results in the main thread blocking forever.
To resolve this issue, in this PR we remove `join_workers` completely since it
is not necessary to wait for daemon threads.
#Closes: https://github.com/pytorch/pytorch/issues/53413
ghstack-source-id: 123641509
Test Plan:
1) Tested with repro in
https://github.com/pytorch/pytorch/issues/53413.
2) Hard to add a unit test for this since the bug really depends on order of
objects being destroyed.
Reviewed By: rohan-varma
Differential Revision: D26863321
fbshipit-source-id: 18fff072cabacfb10390e971eac789859d3dcc81
