as in main(), we use `stop_signal` to handle SIGINT and SIGTERM,
so when scylla receives a SIGTERM, the corresponding signal handler
could get called on any threads created by this program. so there
is chance that the alien_runner thread could be choosen to run the
signal handler setup by `main()`, but that signal handler assumes
the availability of Seastar reactor. unfortunately, we don't have
a Seastar reactor in alien thread. the same applies to Seastar's
`thread_pool` which handles the slow and blocking POSIX calls typically
used for interacting with files.
so, in this change, we use the same approach as Seastar's
`thread_pool::work()` -- just block all signals, so the alien threads
used by wasm for compiling UDF won't handle the signals using the
handlers planted by `main()`.
Fixes#13228
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes#13233
0ba6627d5c