lkml.org 
[lkml]   [2019]   [Sep]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] net/skbuff: silence warnings under memory pressure
On Thu, 05 Sep 2019 12:03:13 -0400
Qian Cai <cai@lca.pw> wrote:

> > > 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

\
 
 \ /
  Last update: 2019-09-05 19:15    [W:0.181 / U:2.400 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site