Date: Fri, 16 Feb 1996 22:18:55 +1100 From: Bruce Evans <bde@zeta.org.au> To: babkin@hq.icb.chel.su, bde@zeta.org.au Cc: hackers@freebsd.org Subject: Re: Digi patch Message-ID: <199602161118.WAA07943@godzilla.zeta.org.au>
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>There is a fix for the bug reported to me by Alexis Yashin (sometimes
>the process hangs when closing digi port). Commit it please.
>Thank you!
>*** dgb.c 1996/02/05 04:35:28
>--- dgb.c 1996/02/05 04:40:17
>***************
>*** 1386,1391 ****
>--- 1386,1392 ----
> }
> #ifndef TS_ASLEEP /* post 2.0.5 FreeBSD */
> ttwwakeup(tp);
>+ wakeup(TSA_OCOMPLETE(tp));
> #else
> if(tp->t_state & TS_ASLEEP) {
> tp->t_state &= ~TS_ASLEEP;
Er, it's wrong. Processes sleeping on TSA_OCOMPLETE(tp) should not be
woken up until output is complete. ttwwakeup() does this. Output is
complete if t_outq is empty and the TS_BUSY bit is clear. The bug is
probably that TS_BUSY doesn't get cleared properly. TS_BUSY apparently
gets cleared in the next call to t_oproc() - otherwise ttywait() would
loop forever waking itself up. The extra wakeup would be harmless if
this livelock wasn't a possibility.
Bruce
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