Re: [PATCH tty 1/1] serial: 8250: Change console_msr_work to IRQ_WORK_LAZY

[Sebastian Andrzej Siewior]

On 2026-08-28 18:04:08 [+0206], John Ogness wrote:
> For some platforms it is a problem to queue irq_work when entering
> cpuidle states. Since irq_work is used for deferred MSR handling,
> any atomic console printing when entering cpuidle states can lead
> to the affected hardware hanging. Tegra20 and Tegra30 are examples
> of such platforms. Avoiding raising the irq_work IRQ has shown to
> circumvent the problem.

I would argue that this is done for the benefit of less interrupts since
there no need to handle console_msr_work immediately. With the side
effect that it might fix a bug that was not yet reported on Tegra[23]0. 

Ideally the Tegra folks should figure out what exactly is broken instead
of adding duct tape everywhere else.

> Change the console_msr_work to be IRQ_WORK_LAZY, thus not raising
> an IRQ upon irq_work queuing. The irq_work is then handled on the
> next interrupt (worst case, kernel tick).

Not on the next interrupt, on the next jiffies tick. Should you run
tickless and should the CPU have the tick switch off then it will raise
the irq-work interrupt anyway.

side-note: Wasn't there another tegra workaround in v5/take1?

Sebastian