Subject: Re: Sane exit from a program on receipt of a signal
To: None <>
From: ITOH Yasufumi <>
List: tech-userlevel
Date: 07/21/2007 21:27:24
mouse@Rodents.Montreal.QC.CA writes:
> > As for SIGTSTP and other tty signals, the signal should be sent to
> > the process group rather than to just the current process.
> I disagree.

Take a look at curses(3) and other SIGTSTP-aware software.
You will easily find kill(0, SIGTSTP).

Stopping only one process of a process group will cause serious problems
with BSD job control and must be avoided.

> If it was generated from the tty, it's *already* been sent to other
> processes in the foreground process group; sending it again would be
> wrong (and could lose big due to our send racing against the other
> process handling it).  If it was sent to this process specifically,
> rebroadcasting it to the whole process group just so *we* can handle it
> with the default action is equally wrong.

Neither is wrong.

BSD is carefully designed to allow kill(0, SIGTSTP) in the former case.
Sending SIGTSTP to already stopped processes is ignored happily.

In the latter case, stopping one process of a process group may left
the terminal in unusable state, and stopping the process group is
user's benefit.

ITOH Yasufumi