GIL acquire needed in ValueCache::trimPrefixes (#81061)
Summary: Dubugged a segfault issue in Ondemand python tracing. Committing as a a separate diff from D37410204.
Test Plan:
- run a python test case with the following command for on-demand flow:
echo -e "PYTHON_STACK_TRACE=true" > /tmp/scott_kineto.conf && dyno gputrace --gputrace_duration 300ms --gpuconf /tmp/scott_kineto.conf
Reviewed By: chaekit
Differential Revision: D37662988
Pull Request resolved: https://github.com/pytorch/pytorch/pull/81061
Approved by: https://github.com/albanD
