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ttydev_write: prevent stops while terminal is busied

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Since busy state is checked by all blocked writes, stopping a process
which waits in ttydisc_write() causes cascade.  Utilize sigdeferstop()
to avoid the issue.

Submitted by:	Jakub Piecuch <j.piecuch96@gmail.com>
PR:	255816
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2021-05-13 04:35:06 +03:00
parent cc6f46ac2f
commit 8cf912b017
1 changed files with 3 additions and 1 deletions
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4
sys/kern/tty.c
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@ -525,7 +525,7 @@ static int
ttydev_write(struct cdev *dev, struct uio *uio, int ioflag)
{
struct tty *tp = dev->si_drv1;
int error;
int defer, error;
error = ttydev_enter(tp);
if (error)
@ -549,7 +549,9 @@ ttydev_write(struct cdev *dev, struct uio *uio, int ioflag)
}
tp->t_flags |= TF_BUSY_OUT;
defer = sigdeferstop(SIGDEFERSTOP_ERESTART);
error = ttydisc_write(tp, uio, ioflag);
sigallowstop(defer);
tp->t_flags &= ~TF_BUSY_OUT;
cv_signal(&tp->t_outserwait);
}