Re: [PATCH] net/skbuff: silence warnings under memory pressure

On Thu, 05 Sep 2019 12:03:13 -0400
Qian Cai [off-list ref] wrote:

quoted

quoted

and could deal with console hardware that involve irq_exit() anyway.  

printk->console_driver->write() does not involve irq.  

Hmm, from the article,

https://en.wikipedia.org/wiki/Universal_asynchronous_receiver-transmitter

"Since transmission of a single or multiple characters may take a long time
relative to CPU speeds, a UART maintains a flag showing busy status so that the
host system knows if there is at least one character in the transmit buffer or
shift register; "ready for next character(s)" may also be signaled with an
interrupt."

I'm pretty sure all serial consoles do a busy loop on the UART and not
use interrupts to notify when it's available. That would require an
asynchronous implementation of printk() which would be quite complex to
implement.

-- Steve