daemonStreamEvent() holds priv->lock across its whole body and closes the client from every error path. The close hook runs in the same thread and takes priv->lock again, so the daemon main loop deadlocks against itself and the host stops answering RPC entirely while its guests keep running. Only a restart of the daemon recovers.
We hit this in the field on 9.5.0, and current master is affected the same way. Getting there needs a client already marked wantClose while one of its streams still delivers events, which is presumably why it has gone unnoticed since 9.2.0. Patch 1 closes the client after the lock guard has gone out of scope. Patch 2 adds a test for it, which needs remote_daemon_stream.c compiled into a test binary; that is the only build change and it pulls in the generated protocol headers via remote_daemon.h. The test deadlocks without patch 1 and passes with it. Signed-off-by: Denis V. Lunev <[email protected]> Denis V. Lunev (2): remote: fix daemon deadlock when a stream event closes its client tests: add daemonstreamtest covering the stream close deadlock src/remote/meson.build | 7 +- src/remote/remote_daemon_stream.c | 58 ++++---- tests/daemonstreamtest.c | 212 ++++++++++++++++++++++++++++++ tests/meson.build | 9 ++ 4 files changed, 262 insertions(+), 24 deletions(-) create mode 100644 tests/daemonstreamtest.c base-commit: 91d4618734bd6d02174b909aadb7d84a99560ebe -- 2.53.0
