Re: [PATCH 0/5] Fix deadlock on runtime suspend in DRM drivers

Lukas Wunner
2018-02-15T05:38:44Z

On Wed, Feb 14, 2018 at 09:58:43AM -0500, Sean Paul wrote:
> On Wed, Feb 14, 2018 at 03:43:56PM +0100, Michel Dänzer wrote:
> > On 2018-02-14 03:08 PM, Sean Paul wrote:
> > > On Wed, Feb 14, 2018 at 10:26:35AM +0100, Maarten Lankhorst wrote:
> > >> Op 14-02-18 om 09:46 schreef Lukas Wunner:
> > >>> On Sun, Feb 11, 2018 at 10:38:28AM +0100, Lukas Wunner wrote:
> > >>>> Fix a deadlock on hybrid graphics laptops that's been present since 2013:
> > >>> This series has been reviewed, consent has been expressed by the most
> > >>> interested parties, patch [1/5] which touches files outside drivers/gpu
> > >>> has been acked and I've just out a v2 addressing the only objection
> > >>> raised. My plan is thus to wait another two days for comments and,
> > >>> barring further objections, push to drm-misc this weekend.
> > >>>
> > >>> However I'm struggling with the decision whether to push to next or
> > >>> fixes. The series is marked for stable, however the number of
> > >>> affected machines is limited and for an issue that's been present
> > >>> for 5 years it probably doesn't matter if it soaks another two months
> > >>> in linux-next befor it gets backported. Hence I tend to err on the
> > >>> side of caution and push to next, however a case could be made that
> > >>> fixes is more appropriate.
> > >>>
> > >>> I'm lacking experience making such decisions and would be interested
> > >>> to learn how you'd handle this.
> > >>
> > >> I would say fixes, it doesn't look particularly scary. :)
> > >
> > > Agreed. If it's good enough for stable, it's good enough for -fixes!
> >
> > It's not that simple, is it? Fast-tracking patches (some of which appear
> > to be untested) to stable without an immediate cause for urgency seems
> > risky to me.
>
> /me should be more careful what he says
>
> Given where we are in the release cycle, it's barely a fast track.
> If these go in -fixes, they'll get in -rc2 and will have plenty of
> time to bake. If we were at rc5, it might be a different story.

The patches are marked for stable though, so if they go in through
drm-misc-fixes, they may appear in stable kernels before 4.16-final
is out. Greg picks up patches once they're in Linus' tree, though
often with a delay of a few days or weeks. If they go in through
drm-misc-next, they're guaranteed not to appear in *any* release
before 4.16-final is out.

This allows for differentiation between no-brainer stable fixes that
can be sent immediately and scarier, but similarly important stable
fixes that should soak for a while. I'm not sure which category
this series belongs to, though it's true what Maarten says, it's
not *that* grave a change.

Thanks,

Lukas
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