Re: [PATCH 1/2] bug: Provide WARN_ON.*DEFERRED() macros for console deferred output

[Petr Mladek]

On Wed 2026-06-24 17:24:31, Sebastian Andrzej Siewior wrote:
> On 2026-06-24 11:17:31 [+0200], Petr Mladek wrote:
> > For Linus, it was a no-go, definitely.
> …
> > I would vote for adding the WARN_*DEFERRED() into the scheduler code
> > at least until majority of console drivers are converted to nbcon API.
> 
> I see four nbcon serial console drivers (+netconsole, + drm_log). We
> have at least four times that many console drivers. What is the
> majority from your point of view? The 8250 should cover all of x86.

Good question. IMHO, there are about 100 console drivers:

$> git grep "struct console.*= {" | wc -l
107

But I guess that many of them are some old rarely used ones.

I tried to google amount of market share from various architectures
and it seems that most spread are: arm, x86_64, and risc-v.

Arm might already be mostly covered by pl011.
x86_64 will be covered by 8250.

I am not sure about risc-v. It seems that it might use 8250 as well
at least in virtual machines. Also there is drivers/tty/hvc/hvc_riscv_sbi.c.

Hmm, 8250 might the breakpoint. Maybe, we could leave the rest as a
motivation to convert the console driver instead of adding workarounds
using the printk_deferred() mechanism.

That said, AFAIK, the netconsole is often used when the device does
not have a serial console. And it is pity that it does not have
the .write_atomic callbacks implemented.

Best Regards,
Petr