linux-kernel - Re: [PATCH] hwmon: (fam15h_power) Disable preemption when reading registers

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Date:	Wed, 1 Jun 2016 11:15:09 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Ingo Molnar <mingo@...nel.org>, linux-hwmon@...r.kernel.org,
	X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	Rui Huang <ray.huang@....com>,
	Sherry Hurwitz <sherry.hurwitz@....com>
Subject: Re: [PATCH] hwmon: (fam15h_power) Disable preemption when reading
 registers

On Wed, Jun 01, 2016 at 03:41:26PM +0200, Borislav Petkov wrote:
> On Wed, Jun 01, 2016 at 06:22:59AM -0700, Guenter Roeck wrote:
> > An explanation would be helpful. Is this a bug fix ?
> 
> That's a good point - yes, it is necessary. Both smp_processor_id()
> *and* smp_call_function_many() need to be called with preemption
> disabled.
> 
> It did fire the BUG thing in check_preemption_disabled() with 4.7-rc1
> here without those fixes.
> 
It would be great if you can add at least part of the BUG message as well
as a Fixes: tag into the patch description. If you had, I would not have
asked, saving both of us time ;-).

> But, we need the other patch too -
> 
> "[PATCH] x86/cpu/AMD: Extend X86_FEATURE_TOPOEXT workaround to newer models"
> 
> because the cpumask generation in read_registers() doesn't work on those
> Carrizo CPUs.
> 
> IINM, the breakage came in during this merge window so we don't have to
> CC:stable but both should be sent to Linus as fixes for 4.7.
> 
> You could sync with Ingo who takes/acks what... but they could go
> through tip and hwmon tree too, I don't see a hard dependency between
> the two - they'd only need to be in 4.7-final.
> 

Sounds like separate trees should be fine then.

Thanks,
Guenter