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

panic()
bust_spinlocks(1) // sets oops_in_progress
console_flush_on_panic()
call_console_drivers()
-> serial_driver_write()
if (oops_in_progress)
locked = spin_trylock_irqsave(&port->lock);
uart_console_write();
if (locked)
spin_unlock_irqrestore(&port->lock);

-ss

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