Messages in this thread | | | Date | Wed, 3 Aug 2022 18:34:30 +0200 | From | Sebastian Andrzej Siewior <> | Subject | Re: [GIT PULL] printk for 5.20 |
| |
On 2022-08-03 09:08:07 [-0700], Linus Torvalds wrote: > But thinking some more about it, even the "serious RT" people almost > certainly don't really want some kind of static "disable it all". Not > even if it was a separate Kconfig question like I suggested. > > You'd most likely want it to be dynamic, because things like "log to > console" is different at bootup when the system hasn't started yet - > you can't really have realtime response when your hardware hasn't even > initialized yet - and when things are actually running. > > So I think even then you really just want a "turn off console logging" > dynamic flag, not a Kconfig option.
Having such a flag would mean we have to set it starting with SYSTEM_SCHEDULING because otherwise we risk a deadlock once the console driver tries to acquire its lock. The printk code invokes the console drivers with disabled interrupts and the console driver use spinlock_t locking which become sleeping locks on PREEMPT_RT and must not be acquired with disabled interrupts. The long term solution is to have a printing thread for the console driver and the atomic console support to print directly in an emergency case.
> Which I think we already have, in the form of log levels. No? > > Linus
Sebastian
| |