Ceph » CephFS

Using signals to abruptly kill the MDS has a few issues:

- teuthology logs are polluted with stacktraces
- coredumps are generated and need cleaned up. These cores are not useful.
- signal handlers are invoked and allow some threads of the MDS to continue executing
- signal handlers may use malloc and lock up the mds

Instead, use the _exit syscall to stop the MDS immediately with an abnormal exit code*. This will immediately stop all threads atomically in the kernel, not generate a coredump, and quietly log to the teuthology.log.

Beyond changing the syscall, the qa suite will need cleaned up to stop looking for cores and may need adjustments to look for genuine exits instead of abnormal termination via signals.

• I'm using exit code 120 in the ceph-mgr in https://github.com/ceph/ceph/pull/56997