[v2] nbcon irq_work fixes

[PATCH printk v2 0/2] nbcon irq_work fixes

Posted by John Ogness 4 weeks, 1 day ago

Hi,

This is v2 of a series to address some irq_work issues with nbcon.
Initially motivated as a workaround for hardware-related regressions
reported [0], it turns out that the workaround is actually a nice
improvement for nbcon deferred printing in general.

v1 is here [1].

John Ogness

The changes since v1:

- Add a preceding patch to flush the irq_work on nbcon_free(). This
  pre-existing issue was reported [2] by Sashiko while it was
  reviewing v1.

[0] https://lore.kernel.org/lkml/f3757a75-0ba1-4558-bf57-f19ab7e59a4c@nvidia.com
[1] https://lore.kernel.org/lkml/20260827184750.203521-1-john.ogness@linutronix.de
[2] https://sashiko.dev/#/patchset/20260827184750.203521-1-john.ogness%40linutronix.de

John Ogness (2):
  printk/nbcon: Flush nbcon_irq_work in nbcon_free()
  printk/nbcon: Change nbcon_irq_work to IRQ_WORK_LAZY

 kernel/printk/nbcon.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)


base-commit: ffe0486b139e45cd9c9ca2584f04a1910fe4f8a6
-- 
2.47.3

Re: [PATCH printk v2 0/2] nbcon irq_work fixes

Posted by Bradley Morgan 4 weeks ago

On 28 August 2026 15:02:07 BST, John Ogness <john.ogness@linutronix.de>
wrote:
>Hi,
>
>This is v2 of a series to address some irq_work issues with nbcon.
>Initially motivated as a workaround for hardware-related regressions
>reported [0], it turns out that the workaround is actually a nice
>improvement for nbcon deferred printing in general.
>
>v1 is here [1].
>
>John Ogness
>
>The changes since v1:
>
>- Add a preceding patch to flush the irq_work on nbcon_free(). This
>  pre-existing issue was reported [2] by Sashiko while it was
>  reviewing v1.
>
>[0]
>https://lore.kernel.org/lkml/f3757a75-0ba1-4558-bf57-f19ab7e59a4c@nvidia.com
>[1]
>https://lore.kernel.org/lkml/20260827184750.203521-1-john.ogness@linutronix.de
>[2]
>https://sashiko.dev/#/patchset/20260827184750.203521-1-john.ogness%40linutronix.de
>
>John Ogness (2):
>  printk/nbcon: Flush nbcon_irq_work in nbcon_free()
>  printk/nbcon: Change nbcon_irq_work to IRQ_WORK_LAZY
>
> kernel/printk/nbcon.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
>
>base-commit: ffe0486b139e45cd9c9ca2584f04a1910fe4f8a6
>
Tested-by: Bradley Morgan <brads@mainlining.org> # PKVM, based on Pixel 7 (ARM64)



--- Thanks!
https://lore.kernel.org/all/EE579805-42F2-4C58-B752-F28779EEB717@grrlz.net/

Re: [PATCH printk v2 0/2] nbcon irq_work fixes

Posted by Sebastian Andrzej Siewior 3 weeks, 5 days ago

On 2026-08-29 00:39:15 [+0100], Bradley Morgan wrote:
> Tested-by: Bradley Morgan <brads@mainlining.org> # PKVM, based on Pixel 7 (ARM64)

Does this PKVM even use a nbcon and if so which one?

Sebastian

Re: [PATCH printk v2 0/2] nbcon irq_work fixes

Posted by Bradley Morgan 3 weeks, 5 days ago

On 31 August 2026 07:36:48 BST, Sebastian Andrzej Siewior
<bigeasy@linutronix.de> wrote:
>On 2026-08-29 00:39:15 [+0100], Bradley Morgan wrote:
>> Tested-by: Bradley Morgan <brads@mainlining.org> # PKVM, based on Pixel
>7 (ARM64)
>
>Does this PKVM even use a nbcon and if so which one?
>

heh, not PKVM itself, I booted a kernel inside PKVM, which is the
hypervisor, the kernel has nbcon inside. My T-B is for the kernel 

>Sebastian

--- Thanks!
https://lore.kernel.org/all/EE579805-42F2-4C58-B752-F28779EEB717@grrlz.net/

Re: [PATCH printk v2 0/2] nbcon irq_work fixes

Posted by Sebastian Andrzej Siewior 3 weeks, 5 days ago

On 2026-08-31 08:31:22 [+0100], Bradley Morgan wrote:
> On 31 August 2026 07:36:48 BST, Sebastian Andrzej Siewior
> <bigeasy@linutronix.de> wrote:
> >On 2026-08-29 00:39:15 [+0100], Bradley Morgan wrote:
> >> Tested-by: Bradley Morgan <brads@mainlining.org> # PKVM, based on Pixel
> >7 (ARM64)
> >
> >Does this PKVM even use a nbcon and if so which one?
> >
> 
> heh, not PKVM itself, I booted a kernel inside PKVM, which is the
> hypervisor, the kernel has nbcon inside. My T-B is for the kernel 

That tested-by is futile if none of the suggested changes were actually
tested.

Sebastian

Re: [PATCH printk v2 0/2] nbcon irq_work fixes

Posted by Petr Mladek 3 weeks, 5 days ago

On Mon 2026-08-31 10:22:37, Sebastian Andrzej Siewior wrote:
> On 2026-08-31 08:31:22 [+0100], Bradley Morgan wrote:
> > On 31 August 2026 07:36:48 BST, Sebastian Andrzej Siewior
> > <bigeasy@linutronix.de> wrote:
> > >On 2026-08-29 00:39:15 [+0100], Bradley Morgan wrote:
> > >> Tested-by: Bradley Morgan <brads@mainlining.org> # PKVM, based on Pixel
> > >7 (ARM64)
> > >
> > >Does this PKVM even use a nbcon and if so which one?
> > >
> > 
> > heh, not PKVM itself, I booted a kernel inside PKVM, which is the
> > hypervisor, the kernel has nbcon inside. My T-B is for the kernel 
> 
> That tested-by is futile if none of the suggested changes were actually
> tested.

Yeah, I am going to omit this tested-by tag if I remember to remove
it from the patch generated by b4.

Best Regards,
Petr

PS: Bradley, this is not a good way to become part of the kernel
    community. The tested-by flag would be valuable only when
    the modified code was used during the test.

Re: [PATCH printk v2 0/2] nbcon irq_work fixes

Posted by Bradley Morgan 3 weeks, 5 days ago

On 31 August 2026 09:22:37 BST, Sebastian Andrzej Siewior
<bigeasy@linutronix.de> wrote:
>On 2026-08-31 08:31:22 [+0100], Bradley Morgan wrote:
>> On 31 August 2026 07:36:48 BST, Sebastian Andrzej Siewior
>> <bigeasy@linutronix.de> wrote:
>> >On 2026-08-29 00:39:15 [+0100], Bradley Morgan wrote:
>> >> Tested-by: Bradley Morgan <brads@mainlining.org> # PKVM, based on
>Pixel
>> >7 (ARM64)
>> >
>> >Does this PKVM even use a nbcon and if so which one?
>> >
>> 
>> heh, not PKVM itself, I booted a kernel inside PKVM, which is the
>> hypervisor, the kernel has nbcon inside. My T-B is for the kernel 
>
>That tested-by is futile if none of the suggested changes were actually
>tested.
>
>Sebastian
urgh im on holiday, I'll elaborate later.
--- Thanks!
https://lore.kernel.org/all/EE579805-42F2-4C58-B752-F28779EEB717@grrlz.net/

Re: [PATCH printk v2 0/2] nbcon irq_work fixes

Posted by Jon Hunter 4 weeks, 1 day ago

Hi John,

On 28/08/2026 15:02, John Ogness wrote:
> Hi,
> 
> This is v2 of a series to address some irq_work issues with nbcon.
> Initially motivated as a workaround for hardware-related regressions
> reported [0], it turns out that the workaround is actually a nice
> improvement for nbcon deferred printing in general.
> 
> v1 is here [1].
> 
> John Ogness
> 
> The changes since v1:
> 
> - Add a preceding patch to flush the irq_work on nbcon_free(). This
>    pre-existing issue was reported [2] by Sashiko while it was
>    reviewing v1.
> 
> [0] https://lore.kernel.org/lkml/f3757a75-0ba1-4558-bf57-f19ab7e59a4c@nvidia.com
> [1] https://lore.kernel.org/lkml/20260827184750.203521-1-john.ogness@linutronix.de
> [2] https://sashiko.dev/#/patchset/20260827184750.203521-1-john.ogness%40linutronix.de
> 
> John Ogness (2):
>    printk/nbcon: Flush nbcon_irq_work in nbcon_free()
>    printk/nbcon: Change nbcon_irq_work to IRQ_WORK_LAZY
> 
>   kernel/printk/nbcon.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)

I have tested these on Tegra and all is working well, so for
the series ...

Tested-by: Jon Hunter <jonathanh@nvidia.com>

Thanks for fixing this!

Cheers
Jon

-- 
nvpublic