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

On Thu, Sep 20, 2018 at 10:25:01AM -0400, Mikulas Patocka wrote:
>
>
> On Wed, 19 Sep 2018, Dmitry Safonov wrote:
>
> > On Wed, 2018-09-19 at 16:03 -0400, Mikulas Patocka wrote:
> > >
> > > On Wed, 19 Sep 2018, Dmitry Safonov wrote:
> > > > Thanks much for the testing, Mikulas.
> > > > Could you try to bisect which of the patches causes it?
> > > > The most important are 1,2,3 - probably, one of them caused it..
> > > > I'll stare a bit into the code.
> > >
> > > The patch 3 causes it.
> > >
> > > The hangs during reboot take either 80 seconds, 3 minutes or 3:25.
> >
> > Thanks much for that again.
> > Any chance you have sysrq enabled and could print: locks held in system
> > and kernel backtraces for applications?
>
> Stacktrace doesn't work on parisc. It used to work on 4.18, but the kernel
> 4.19 reportedly requires patched binutils.
>
> Mikulas
>
> > I suppose, userspace hangs in n_tty_receive_buf_common(), which is
> > better of cause than null-ptr dereference, but I believe we can improve
> > it by stopping a reader earlier if there is any writer pending.
> >
> > --
> > Thanks,
> > Dmitry
> >

Any progress here? Or is more info/stacktrace needed about the hang?


Thanks,

-- Pasi

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