Status of reverted Linux patch "tty: Fix ldisc crash on reopened tty", Linux 4.9 kernel frequent crashes
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/?i...
but then reverted here: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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;#26...
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.
Thanks a lot,
-- Pasi
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/?i...
but then reverted here: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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;#26...
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 looked briefly at the patch and related discussion on the kernel mailing lists and it seemed to be reverted not due to any problems it caused with kernel behavior but rather due to concerns about insufficient review before it was committed and possible merge conflicts.
The issue is the problem doesn't appear to have been discussed any further on the kernel mailing lists since April, and I'm not sure why. My inclination would be to start back up discussion upstream and try to get clarification as to why the patch has remained reverted and there's been no effort to bring it back into the kernel, rather than assume the patch is safe to use. I doubt anyone else but people experiencing the issue have it up on their radar.
The 4.9 virt kernel does have some patches currently that haven't (yet) been accepted upstream, so it's definitely an option to do that here. As far as I know, nothing really gets pushed back upstream. Most often the patches are just plucked from upstream mailing lists before they get merged into an official upstream release.
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/?i...
but then reverted here: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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;#26...
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.
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/?i...
but then reverted here: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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;#26...
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
On 09/20/2017 03:10 AM, Pasi Kärkkäinen wrote:
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
It has already been built into the latest test kernel .. 4.9.48-29.el7
On Wed, Sep 20, 2017 at 04:49:10AM -0500, Johnny Hughes wrote:
On 09/20/2017 03:10 AM, Pasi Kärkkäinen wrote:
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
It has already been built into the latest test kernel .. 4.9.48-29.el7
Oh, I missed that. Thanks a lot!
-- Pasi
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Johnny Hughes -
Kevin Stange -
Nathan March -
Pasi Kärkkäinen