[C++][ArrowFlight] Crash due to UCS thread mode

[amirgon]

Describe the bug, including details regarding any error messages, version, and platform.

ArrowFlight UCX transport sets UCS_THREAD_MODE_SERIALIZED mode:

arrow/cpp/src/arrow/flight/transport/ucx/ucx_client.cc

Line 100 in fd6bf5a

worker_params.thread_mode = UCS_THREAD_MODE_SERIALIZED;

This can cause UCX to crash (mpool corruption).
This happens when buffer is deallocated on a different thread. In such case two threads access UCX memory pool simultaneously.
To fix that, need to change thread mode to UCS_THREAD_MODE_MULTI.

See discussion on UCX forum: openucx/ucx#9987

Opened a PR: #43120

Component(s)

C++, FlightRPC

[lidavidm]

Issue resolved by pull request 43120
#43120