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Re: kern/46522

The following reply was made to PR kern/46522; it has been noted by GNATS.

From: David Laight <>
Subject: Re: kern/46522
Date: Mon, 4 Jun 2012 10:06:18 +0100

 On Mon, Jun 04, 2012 at 02:40:05AM +0000, Nat Sloss wrote:
 >  I have a marginally better patch as it was a bad idea to sleep whilst 
 > holding 
 >  proc_lock it would cause it to hang and be unresponsive.
 >  @@ -2770,9 +2774,11 @@
 >                  sigemptyset(&tp->t_sigs[i]);
 >          if (tp->t_sigcount != 0)
 >                  TAILQ_REMOVE(&tty_sigqueue, tp, t_sigqueue);
 >  -       mutex_exit(&tty_lock);
 >          mutex_exit(proc_lock);
 >  +       ttysleep(tp, &tp->t_rawcv, true, mstohz(200));
 >  +       mutex_exit(&tty_lock);
 >  +
 While adding a fixed sleep is enough to show where the problem
 lies, it isn't an appropriate solution to the problem.
 You need to properly wait for the close to release a reference
 count on the resource, and then free the relevant data areas.
 The scheduler can always decide to not run the process you
 are waiting for - so the sleep has to be indefinitely long.
 I;m not saying a real fix is easy! the tty subsystem is full
 of places where it isn't remotely MP-safe.
 David Laight:

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