Re: [PATCH 1/3] mm: Check if mmu notifier callbacks are allowed to fail

Michal Hocko
2018-11-23T12:44:02Z

On Fri 23-11-18 13:30:57, Daniel Vetter wrote:
> On Fri, Nov 23, 2018 at 12:15:57PM +0100, Michal Hocko wrote:
> > On Thu 22-11-18 17:51:04, Daniel Vetter wrote:
> > > Just a bit of paranoia, since if we start pushing this deep into
> > > callchains it's hard to spot all places where an mmu notifier
> > > implementation might fail when it's not allowed to.
> >
> > What does WARN give you more than the existing pr_info? Is really
> > backtrace that interesting?
>
> Automated tools have to ignore everything at info level (there's too much
> of that). I guess I could do something like
>
> if (blockable)
> pr_warn(...)
> else
> pr_info(...)
>
> WARN() is simply my goto tool for getting something at warning level
> dumped into dmesg. But I think the pr_warn with the callback function
> should be enough indeed.

I wouldn't mind s@pr_info@pr_warn@

> If you wonder where all the info level stuff happens that we have to
> ignore: suspend/resume is a primary culprit (fairly important for
> gfx/desktops), but there's a bunch of other places. Even if we ignore
> everything at info and below we still need filters because some drivers
> are a bit too trigger-happy (i915 definitely included I guess, so everyone
> contributes to this problem).

Thanks for the clarification.
--
Michal Hocko
SUSE Labs