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SubjectRe: [PATCH v2 03/28] vsprintf: %pf(%p)
On Fri, May 20, 2022 at 09:40:24AM +0200, Michal Hocko wrote:
> On Thu 19-05-22 13:23:56, Kent Overstreet wrote:
> [...]
> > The goal is to replace most of our %p format extensions with this
> > interface, and to move pretty-printers out of the core vsprintf.c code -
> > this will get us better organization and better discoverability (you'll
> > be able to cscope to pretty printer calls!), as well as eliminate a lot
> > of dispatch code in vsprintf.c.
>
> Is this really something that we want? While I do see arguments about
> our existing %p$FOO mess there is at least one good argument to have all
> those "pretty printers" at a single location. That approach allows to do
> a proper review whether those printers are safe from the printk point of
> view. If we allow any random callback to be called from the printk
> context we just give a free ticket to anybody to do whatever from there
> without understanding of all potential consequences.
>
> Maybe that is less of a concern these days when printk locking has been
> reworked a lot but I still do remember how frustrating it is to debug
> issues related to printk getting stuck...

So for now, I added a note in the documentation that pretty-printers may not
sleep if passed to printk() - but if they're just passed to pr_buf() or
sprintf() it's completely fine.

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