Re: [RFC][PATCHv3 2/5] printk: introduce printing kernel thread

Steven Rostedt
2017-06-30T13:33:15Z

On Fri, 30 Jun 2017 21:42:24 +0900
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> wrote:

> I apply a very simple litmus test. if the answer to the question
> "so we leave console_unlock() and there are pending messages,
> who and when is going to flush the remaining messages?" is
> "something sometime in the future" then it's a no-no.

I totally agree with this, but...

>
> "something sometime in the future" is equal to "no one".
>
> we must stay and continue printing. because it gives the right
> answer - "current process and right now. until someone else
> (+printk_kthread) takes over".

Would it be acceptable to have a user knob that allows for it not to
happen? That is, let the user of the kernel decide if they care about
critical prints or not? If a knob says, "only print X, then offload"
would that be allowed. Of course the default would be "only print ALL
OF IT" to keep the current behavior.

A lot of times the console isn't recorded to debug hard lock ups. I
know most desktops running a GUI do not. When ever my workstation locks
up, and it has no serial, I don't get to see the dmesg at all. In this
situation, I don't care if the prints are offloaded or not.

-- Steve