Re: [PATCH printk v4 00/15] implement threaded console printing

[Petr Mladek <pmladek@suse.com>]

On Thu 2022-04-21 23:28:35, John Ogness wrote:
> This is v4 of a series to implement a kthread for each registered
> console. v3 is here [0]. The kthreads locklessly retrieve the
> records from the printk ringbuffer and also do not cause any lock
> contention between each other. This allows consoles to run at full
> speed. For example, a netconsole is able to dump records much
> faster than a serial or vt console. Also, during normal operation,
> printk() callers are completely decoupled from console printing.
> 
> There are situations where kthread printing is not sufficient. For
> example, during panic situations, where the kthreads may not get a
> chance to schedule. In such cases, the current method of attempting
> to print directly within the printk() caller context is used. New
> functions printk_prefer_direct_enter() and
> printk_prefer_direct_exit() are made available to mark areas of the
> kernel where direct printing is preferred. (These should only be
> areas that do not occur during normal operation.)
> 
> This series also introduces pr_flush(): a might_sleep() function
> that will block until all active printing threads have caught up
> to the latest record at the time of the pr_flush() call. This
> function is useful, for example, to wait until pending records
> are flushed to consoles before suspending.
> 
> Note that this series does *not* increase the reliability of console
> printing. Rather it focuses on the non-interference aspect of
> printk() by decoupling printk() callers from printing (during normal
> operation). Nonetheless, the reliability aspect should not worsen
> due to this series.

This version looks good enough for linux-next. I do not see any
functional problem and it should work as designed. It is time to
see how it works in various "real life" work loads.

I am going to push it later today unless anyone (John) complains ;-)

Best Regards,
Petr