linux-kernel - Re: [BUG]: Intel uncore boot warning introduced in 4.1

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Date:	Tue, 15 Sep 2015 09:35:45 -0400
From:	Josh Boyer <jwboyer@...oraproject.org>
To:	"Liang, Kan" <kan.liang@...el.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Matthew Leach <matthew@...tleach.net>,
	Ingo Molnar <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
	"eranian@...gle.com" <eranian@...gle.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Vince Weaver <vincent.weaver@...ne.edu>,
	Sonny Rao <sonnyrao@...omium.org>
Subject: Re: [BUG]: Intel uncore boot warning introduced in 4.1

On Mon, Aug 10, 2015 at 9:23 AM, Liang, Kan <kan.liang@...el.com> wrote:
>
>> On Thu, Aug 06, 2015 at 06:10:40PM +0000, Liang, Kan wrote:
>> > The issue may be caused by uncore box initialization.
>> >
>> > For preventing the potential issues of uncore box initialization, I
>> > once moved the uncore_box_init() out of driver initialization in
>> > commit c05199e5a57a579fea1e8fa65e2b511ceb524ffc.
>> >
>> > However, it cause some desktop crash, because the box initialization
>> > codes were moved in IPI context.
>> >
>> > For fixing the crash issue, we had two choice at that time.
>> >  - Simply revert the codes. That's where is
>> > 15c1247953e8a45232ed5a5540f291d2d0a77665 from.
>> >  - Move uncore_box_init out of IPI context to uncore event
>> >    init. I provided a patch for it. https://lkml.org/lkml/2015/4/28/21
>> >   Stephane Eranian also verified it on his platform
>> >
>> > At that time, we chose first option. But it looks there is some issue
>> > now. I guess we may try the second option this time.
>> >
>> > Matthew,
>> >
>> > Could you please revert
>> > 15c1247953e8a45232ed5a5540f291d2d0a77665
>> > and apply the patch https://lkml.org/lkml/2015/4/26/294?
>> > See if it works?
>>
>> That patch is wrong though; how can even publish a PMU which is not
>> initialized?
>
> It's initialized but not in the driver initialization.
> We once encountered boot crashes which caused by uncore
> driver who trying to access non-existing boxes. Also this uncore
> boot warning.
> So I think it's better to move the box init code out of driver
> initialization to prevent such potential boot failures.
> Uncore event init should be a good place to do box init.
> Only when the box is not initialized and user tries to use
> uncore event, we do box initialization.

We're still getting reports of this in Fedora with 4.1.y kernels.  Was
there any resolution to this?

josh
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