cvs commit: src/sys/kern tty.c

[Martin Blapp]

Hi,

Since nobody wants to burn his fingers and touch the tty subsystem,
I've committed this fix as a bandaid to CURRENT and will MCF it after
a week. More work is needed to properly lock and protect the tty subsystem
of course.

During two month of testing this patch stopped the frequent panics we got on
our SMP systems.

I'm willing to do the tty locking changes if someone helps
me to do it and reviews the changes.

--
Martin

On Sun, 10 Sep 2006, Martin Blapp wrote:

> mbr         2006-09-10 16:51:56 UTC
>
>  FreeBSD src repository
>
>  Modified files:
>    sys/kern             tty.c
>  Log:
>  Fix locking race in ttymodem(). The locking of the proctree happens too late
>  and opens a small race window before tp->t_session->s_leader is accessed. In case
>  tp->t_session has just been set to NULL elsewhere, we get a panic().
>
>  This fix is a bandaid until someone else fixes the whole locking in the tty subsystem.
>  Definitly more work needs to be done.
>
>  MFC after:      1 week
>  Reviewed by:    mlaier
>  PR:             kern/103101
>
>  Revision  Changes    Path
>  1.258     +2 -2      src/sys/kern/tty.c
>