tree a1399e0f470f1e7651ba31da5ed7b19b8d2dc011
parent 6884aa3eb00d1a5eb6f9c81a3a00288c13652938
author Willy Tarreau <w@1wt.eu> 1567529702 +0200
committer Willy Tarreau <w@1wt.eu> 1569255277 +0200
encoding latin1

BUG/MEDIUM: check/threads: make external checks run exclusively on thread 1

See GH issues #141 for all the context. In short, registered signal
handlers are not inherited by other threads during startup, which is
normally not a problem, except that we need that the same thread as
the one doing the fork() cleans up the old process using waitpid()
once its death is reported via SIGCHLD, as happens in external checks.

The only simple solution to this at the moment is to make sure that
external checks are exclusively run on the first thread, the one
which registered the signal handlers on startup. It will be far more
than enough anyway given that external checks must not require to be
load balanced on multiple threads! A more complex solution could be
designed over the long term to let each thread deal with all signals
but it sounds overkill.

This must be backported as far as 1.8.