linux-kernel - Re: [GIT PULL] 2 RAS fixes for 3.17, refreshed

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Date:	Fri, 27 Jun 2014 12:59:56 -0400
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Borislav Petkov <bp@...en8.de>
CC:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	x86-ml <x86@...nel.org>, Tony Luck <tony.luck@...el.com>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] 2 RAS fixes for 3.17, refreshed

On 06/27/2014 12:08 PM, Borislav Petkov wrote:
> On Fri, Jun 27, 2014 at 11:12:59AM -0400, Boris Ostrovsky wrote:
>> Yes, it fails because xen_late_init_mcelog() registers /dev/mcelog and (I
>> think) it happens before mcheck_init_device().
> Yes, mcheck_init_device is device_initcall_sync() while
> xen_late_init_mcelog() is device_initcall().
>
>> In other words, misc_register() expected to fail in mcheck/mce.c on
>> (privileged?) PV guests (provided right CONFIG_XEN_* is set).
> So
>
> 	cef12ee52b05 ("xen/mce: Add mcelog support for Xen platform")
>
> made it this way so that xen's init routine runs first.
>
> So it is not the case that misc_register() fails often on xen but it is
> *supposed* to fail by design, when running in dom0. And *then* you need
> the notifier *not* unregistered on the error path so that the timers do
> get deleted properly.
>
> Ok, I see it now. Frankly, I'm not really sure I want to rush this in
> now because it might break something else, Who TF knows what.
>
> Right now my gut feeling tells me we should still queue it for 3.17 and
> have it run for a while in linux-next. We can backport it to stable
> later after some testing...

I don't have a problem with having it soak in linux-next for a while but 
I am not too crazy about releasing 3.16 with this bug (even knowing that 
there will be a backport later). When we hit this problem the results 
are rather unpleasant in that it's not immediately clear what's happened.

We are still at rc2 so we have 3-4 weeks before 3.16 goes out.


-boris


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