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

From: Sergey Senozhatsky <[email-masked]>
Date: Fri, 6 Sep 2019 11:50:22 +0900

On (09/05/19 13:14), Steven Rostedt wrote:
> > 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.

Yes. Besides, we call console drivers with local IRQs disabled.

	-ss