Don Lewis writes:
> } * Archie Cobbs <[EMAIL PROTECTED]> [000317 17:55] wrote:
> } > This bug has been around since at least 2.2.6 and is still present
> } > in RELENG_3, RELENG_4, and -current.
> } >
> } > http://www.freebsd.org/cgi/query-pr.cgi?pr=8324
> } >
> } > Is anyone planning to tackle it? What would be required to fix it?
> } > (it's not clear (to me anyway) from Bruce's description how hard
> } > this is to fix..)
>
> I never heard of using SIGIO for output, but section 6.4 of the daemon
> book says that SIGIO is sent "when a read or write becomes possible".
> On the other hand, section 10.8 (Terminal Operations) mentions SIGIO
> for input but not for output. I also looked at rev 1.1 of kern/tty.c
> and it only sends a SIGIO when input is ready, so this seems to be
> the historical behaviour, so I'm suprised that this program even
> worked with plain tty devices.
>
> } I think Bruce sort of went off into a tangent with his diagnosis,
> } anyhow this is untested (of course :) ), but looks like the right
> } thing to do (from sys_pipe.c).
> }
> } Perhaps the fcntls and ioctls aren't being propogated enough to set
> } the flags properly, but if they are then it should work sort of the
> } way SIGIO does, basically generating a signal for /some condition/
> } on a descriptor.
>
> This patch (vs the 3.4-STABLE version of tty.c) causes SIGIO to be
> sent when a regular or pseudo tty becomes writeable.
>
>
> --- tty.c.orig Sun Aug 29 09:26:09 1999
> +++ tty.c Sat Mar 18 03:09:32 2000
> @@ -2133,6 +2133,8 @@
>
> if (tp->t_wsel.si_pid != 0 && tp->t_outq.c_cc <= tp->t_olowat)
> selwakeup(&tp->t_wsel);
> + if (ISSET(tp->t_state, TS_ASYNC) && tp->t_sigio != NULL)
> + pgsigio(tp->t_sigio, SIGIO, (tp->t_session != NULL));
> if (ISSET(tp->t_state, TS_BUSY | TS_SO_OCOMPLETE) ==
> TS_SO_OCOMPLETE && tp->t_outq.c_cc == 0) {
> CLR(tp->t_state, TS_SO_OCOMPLETE);
>
>
> BTW, I had to add:
> fcntl(1, F_SETOWN, getpid());
> to the test program since there is no longer a default target to send
> the signal to. The old scheme had the defect of sending SIGIO to the
> process group that owned the terminal, which implied that the terminal
> had to be the controlling terminal for the process group. This limited
> a process to only receiving SIGIO from one terminal device even if it
> had more than one open and it wanted to receive SIGIO from all of them.
> Also, SIGIO was sent to the entire process group, but it may be desireable
> to limit this to one process. I wonder if it might make sense to go
> back to the old default for tty devices so that processes only receive
> SIGIO when they are in the foreground ...
Don-
After applying your patch to kern/tty.c and adding the F_SETOWN,
the problem indeed seems to go away..
Is this patch ready to be committed, or do we need more reviewers?
Thanks,
-Archie
___________________________________________________________________________
Archie Cobbs * Whistle Communications, Inc. * http://www.whistle.com
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