On Tue 2024-06-04 01:30:51, John Ogness wrote: > For PREEMPT_RT, legacy console printing is performed in a dedicated > kthread. However, this behavior can also be interesting for other > preemption models as it minimizes the duration of printk() calls by > deferring all printing. > > Provide a new boot argument "threadprintk" that will create the > dedicated kthread for legacy console printing for !PREEMPT_RT > systems. > > The implementation is the same as the "threadirqs" boot argument. > > Users should be aware that if this option is enabled, the shutdown, > reboot, and panic messages probably will not be visible on the > legacy consoles. printk() is _heavily_ limited in this mode. Users would see the messages only when the system is running well. I think that this is a _big_ difference against "threadirqs". It still allows to handle some critical IRQ handlers directly by using IRQF_NO_THREAD. > Non-legacy consoles (NBCON) already have their own dedicated kernel > threads for printing and reliable shutdown, reboot, and panic > printing. This option really only applies to legacy consoles. OK, the NBCON consoles might make it a bit more useful. But there will be only one at the beginning. And it won't work with boot consoles. All I want to say is that this mode has big limitations and kind of weird semantic. This semantic is basically needed only with PREEMPT_RT. I would prefer to remove this patch for now. It would give us more time to think about the threaded and sync modes. Or I would at least use "force" in the name to make it more clear that it forces some non-default (non-optimal) behavior. I would call it "printk_thread_force" or "printk_legacy_thread_force". Best Regards, Petr
