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

Sun Sep 3 12:10:01 UTC 2017
Pasi Kärkkäinen <pasik at iki.fi>

On Sat, Sep 02, 2017 at 08:12:53AM -0500, Johnny Hughes wrote:
> On 08/30/2017 03:10 PM, Pasi Kärkkäinen 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