Re: [RFC PATCH v1 00/25] printk: new implementation

From: Sergey Senozhatsky
Date: Tue Feb 12 2019 - 20:41:49 EST

On (02/12/19 15:29), John Ogness wrote:
> - console_flush_on_panic() currently is a NOP. It is pretty clear how
> this could be implemented if atomic_write was available. But if no
> such console is registered, it is not clear what should be done. Is
> this function really even needed?

If you now rely on a fully preemptible printk kthread to flush
pending logbuf messages, then console_flush_on_panic() is your
only chance to see those pending logbuf messages on the serial
console when the system dies.

Non-atomic consoles should become atomic once you call bust_spinlocks(1),
this is what we currently have:

bust_spinlocks(1) // sets oops_in_progress
-> serial_driver_write()
if (oops_in_progress)
locked = spin_trylock_irqsave(&port->lock);
if (locked)