Re: [PATCH 0/1] printk: Yield console_sem to blocking waiters

[Petr Mladek]

On Wed 2026-09-16 18:22:12, Aruna Ramakrishna wrote:
> 
> > On Sep 11, 2026, at 11:24 AM, Aruna Ramakrishna <aruna.ramakrishna@xxxxxxxxxx> wrote:
> > 
> >> 
> >> On Sep 11, 2026, at 1:08 AM, John Ogness <john.ogness@xxxxxxxxxxxxx> wrote:
> >> 
> >> This Message Is From an External Sender
> >> This message came from outside your organization.
> >> Report Suspicious
> >> On 2026-09-10, Aruna Ramakrishna <aruna.ramakrishna@xxxxxxxxxx> wrote:
> >>> Problem context:
> >>> 
> >>> After a reboot, NetworkManager failed to bring up interfaces because
> >>> systemd was stalled, due to a flood of printk warnings.
> >> 
> >> Note that kernel warnings are considered serious and will put the CPU
> >> into emergency state.
> > 
> > I apologize - I misspoke. These were not KERN_WARNs, rather KERN_INFOs
> > being used by RDS to warn of connection failures etc. A flood of these caused
> > the console_lock starvation.
> > 
> >> 
> >>> Systemd was
> >>> blocked waiting on the console lock for over 122 seconds:
> >> 
> >> Also note that the console lock is related to legacy consoles. Rather
> >> than trying to make the legacy console trainwreck more reliable and
> >> non-interfering, efforts should be spent converting legacy consoles to
> >> NBCON.
> >> 
> >> What console driver are you using?
> >> 
> >> For v7.3 the 8250 driver will be NBCON.
> >> 
> >> John
> >> 
> > 
> > This is for the legacy 8250 serial console.
> > 
> > Thanks,
> > Aruna
> 
> Hi John,
> 
> Even if this patch is not applicable to v7.3, it is still applicable to the older kernel
> versions, right? Will this be considered for the stable tree, without being merged
> upstream first? If yes, would you mind reviewing the patch?

The patch is not acceptable as is. In particular, it does not handle
panic, suspend, various emergency situations where the waiters likely
won't be waken or we do not want to risk the handoff.

I agree with John, let's focus on converting console drivers
to the NBCON API.

I am sorry but I personally do not have time and motivation to review
hacks which would be suitable only for stable.

Best Regards,
Petr