Didier Kryn <kryn@???> writes:
> Le 06/04/2026 à 12:57, Rainer Weikusat via Dng a écrit :
>> Traditionally, the set of pending signal is bitmask, this means only one
>> signal of every kind can be pending at the same time. Judging from code
>> I read yesterday, Linux queues one non-realtime signal but this still
>> only makes two. Since the issue is timing dependent, some fiddling may
>> be necessaary to demonstrate the effect, but this program:
>
>     It is well known that signals can be missed, because of this. You
> can use signalfd() to serialize them, thouth I'm not sure it
> completely grants to not miss any.

The signal manpage (signal(7)) says:

Standard signals do not queue. If multiple instances of a standard
signal are generated while that signal is blocked, then only one
instance of the signal is marked as pending (and the signal will be
delivered just once when it is unblocked). In the case where a
standard signal is already pending, the siginfo_t structure (see
sigaction(2)) associated with that signal is not overwritten on arrival
of subsequent instances of the same signal. Thus, the process will
receive the information associated with the first instance of the
signal.