Re: [PATCH 5.10-rt+] drm/i915/gt: transform irq_disable into local_lock.

From: Steven Rostedt
Date: Tue Nov 16 2021 - 15:25:39 EST


On Sat, 9 Oct 2021 12:49:08 -0400
Joe Korty <joe.korty@xxxxxxxxxxxxxxxxx> wrote:

> On Thu, Oct 07, 2021 at 07:19:29PM +0200, Sebastian Andrzej Siewior wrote:
> > On 2021-10-07 12:59:28 [-0400], Joe Korty wrote:
> > > Convert IRQ blocking in intel_breadcrumbs_park() to a local lock.
> > >
> > > Affects 5.10-rt and all later releases, up to and including when
> > > rt was merged into mainline.
> >
> > RT was merged into mainline? Nobody tells me anything anymore???
> >
> > > This problem has been reported in two other linux-rt-users postings,
> > >
> > > [PREEMPT_RT] i915: fix PREEMPT_RT locking splats (Clark Williams)
> > > [linux-5.12.y-rt] drm/i915/gt: Fix a lockdep warning with interrupts enabled (Jun Miao)
> > >
> > > Neither of these submit the obvious solution, nor,
> > > AFAICT, has either yet been acted on. So I muddy the
> > > waters further by submitting this, a third fix.
> >
> > 5.12 is longer maintained. Could you please take the latest devel tree
> > for testing and participate in
> > https://lore.kernel.org/all/20211005150046.1000285-1-bigeasy@xxxxxxxxxxxxx/
> >
> > If anything I would prefer those patches backported into v5.10 if it is
> > affected.
>
>
> Hi Sebastian,
> Please add my 'Tested-by' to the below patch.
>
> [linux-5.12.y-rt] drm/i915/gt: Fix a lockdep warning with interrupts enabled (Jun Miao)
>
> What was tested was a backport to 5.10-rt. One reject
> was encountered, trivially resolved. No other adjustments
> were made.
>
> My regression tests of last night all passed without any
> of the usual lockdep splats occuring. Prior to this,
> I could be assured of a large enough flood of splats to
> overwhelm the kernel log.
>
> My test stand is a Supermicro C7Z170-SQ. This is tthe
> only system I have on which I could trigger the problem.
>
> I could not find this patch in the 5.12-rt or the 5.15-rt
> tree, so I fetched a copy out of the linux-rt-users
> archives, and backported that.
>
> Tested-by: Joe Korty <joe.korty@xxxxxxxxxxxxxxxxx>

I'm looking to see what needs to be added to 5.10-rt. Is there a particular
fix in one of the 5.x-rt trees (x > 10) that I can pull from? Or is this
only an issue with 5.10 and below?

-- Steve