On Fri, 2020-08-14 at 15:46 -0700, Linus Torvalds wrote:
> On Thu, Aug 13, 2020 at 4:54 AM Sergey Senozhatsky
> <sergey.senozhatsky@xxxxxxxxx> wrote:
> > I think what Linus said a long time ago was that the initial purpose of
> > pr_cont was
> >
> > pr_info("Initialize feature foo...");
> > if (init_feature_foo() == 0)
> > pr_cont("ok\n");
> > else
> > pr_cont("not ok\n");
> >
> > And if init_feature_foo() crashes the kernel then the first printk()
> > form panic() will flush the cont buffer.
>
> Right.
>
> This is why I think any discussion that says "people should buffer
> their lines themselves and we should get rid if pr_cont()" is
> fundamentally broken.
>
> Don't go down that hole. I won't take it. It's wrong.
I don't think it's wrong per se.
It's reasonable to avoid pr_cont when appropriate.
Trivial buffering, or adding and using YA vsprintf
extension can avoid unnecessary message interleaving.
For instance, I just sent this patch to allow removal
of print_vma_addr and its use of pr_cont.
https://lore.kernel.org/lkml/09f11651f0e913e159b955ac447cd8cadf36cb0d.camel@xxxxxxxxxxx/
This is similar to the dump_flags_names removal back
in commit edf14cdbf9a0 ("mm, printk: introduce new format
string for flags")
> The fact is, pr_cont() goes back to the original kernel. No, it wasn't
> pr_cont() back then, and no, there were no actual explicit markers for
> "this is a continuation" at all, it was all just "the last printk
> didn't have a newline, so we continue where we left off".
>
> We've added pr_cont (and KERN_CONT) since then, and I realize that a
> lot of people hate the complexity it introduces, but it's a
> fundamental complexity that you have to live with.
>
> If you can't live with pr_cont(), you shouldn't be working on
> printk(), and find some other area of the kernel that you _can_ live
> with.
>
> It really is that simple.
>
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