Re: [PATCHv5 0/7] tty: Hold write ldisc sem in tty_reopen()

[Mikulas Patocka]

On Wed, 19 Sep 2018, Mikulas Patocka wrote:

> 
> 
> On Tue, 18 Sep 2018, Dmitry Safonov wrote:
> 
> > Hi all,
> > 
> > Three fixes that worth to have in the @stable, as they were hit by
> > different people, including Arista on v4.9 stable.
> > 
> > And for linux-next - adding lockdep asserts for line discipline changing
> > code, verifying that write ldisc sem will be held forthwith.
> > 
> > The last patch is an optional and probably, timeout can be dropped for
> > read_lock(). I'll do it if everyone agrees.
> > (Or as per discussion with Peter in v3, just convert ldisc to
> > a regular rwsem).
> > 
> > Thanks,
> > Dima
> 
> I confirm that this patch series fixes the crash for me.
> 
> Tested-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>

I was too quick to acknowledge this patchset. It doesn't work.

This patchset fixes the crash, but it introduces another bug - when I type 
'reboot' on the console, it prints 'INIT: Switching to runlevel: 6' and 
then it gets stuck for 80 seconds before proceeding with the reboot. When 
I revert this patchset 'reboot' reboots the machine without any delay. 
This bug was reproduced on Debian 5 userspace on pa-risc.

Mikulas