In the Single Unix Spec man page for syslog, I read
LOG_NOWAIT
Do not wait for child processes that may have been created during the course of logging the message.
This option should be used by processes that enable notification of child termination using SIGCHLD,
since syslog() may otherwise block waiting for a child whose exit status has already been collected.
Well, the postmaster certainly enables SIGCHLD, so it seems pretty
dangerous that we don't use this option ...
regards, tom lane