CentOS virt - Sep 2017 - Status of reverted Linux patch "tty: Fix ldisc crash on reopened tty", Linux 4.9 kernel frequent crashes

On Sat, Sep 02, 2017 at 08:12:53AM -0500, Johnny Hughes
wrote:
> On 08/30/2017 03:10 PM, Pasi K?rkk?inen wrote:
> > Hello everyone,
> > 
> > Recently Nathan March reported on centos-virt list he's getting
frequent Linux kernel crashes with Linux 4.9 LTS kernel because of the missing
patch "tty: Fix ldisc crash on reopened tty".
> > 
> > The patch was already merged upstream here:
> >
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=71472fa9c52b1da27663c275d416d8654b905f05
> > 
> > but then reverted here:
> >
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=896d81fefe5d1919537db2c2150ab6384e4a6610
> > 
> > Nathan confirmed if he applies the patch from
71472fa9c52b1da27663c275d416d8654b905f05 to his Linux 4.9 LTS kernel the
bug/problem goes away, so the patch (or similar fix) is still needed, at least
for 4.9 LTS kernel.
> > 
> > 
> > Mikulas reported he's able to trigger the same crash on Linux
4.10:
> > https://www.spinics.net/lists/kernel/msg2440637.html
> >
https://lists.gt.net/linux/kernel/2664604?search_string=ldisc%20reopened;#2664604
> > 
> > Michael Neuling reported he's able to trigger the bug on PowerPC:
> > https://lkml.org/lkml/2017/3/10/1582
> > 
> > 
> > So now the question is.. is anyone currently working on getting this
patch fixed and applied upstream? I think one of the problems earlier was being
able to reliable reproduce the crash.. Nathan says he's able to reproduce it
many times per week on his environment on x86_64.
> > 
> 
> I have no issues rolling this patch in , while we wait on upstream, if
> it makes our tree more stable.
> 
I think we should do that.. What do others think?


Thanks,

-- Pasi

> > I have no issues rolling this patch in , while we wait on upstream, if
> > it makes our tree more stable.
> >
> 
> I think we should do that.. What do others think?
> 
I've had the patch deployed to a group of 32 hosts (with hundreds of vms)
for about 10 days now and no sign of any issues.

So I support it =)

Cheers,
Nathan

On Tue, Sep 05, 2017 at 10:49:13AM -0700, Nathan March
wrote:
> > > I have no issues rolling this patch in , while we wait on
upstream, if
> > > it makes our tree more stable.
> > >
> > 
> > I think we should do that.. What do others think?
> > 
> 
> I've had the patch deployed to a group of 32 hosts (with hundreds of
vms)
> for about 10 days now and no sign of any issues.
> 
> So I support it =)
> 
Thanks Nathan.

Johnny: Can you please add the patch to next Linux 4.9 kernel build? 


Thanks,

-- Pasi
> Cheers,
> Nathan