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

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Date:	Fri, 3 Jun 2016 11:18:36 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	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 Thu, Jun 02, 2016 at 10:14:39AM +0200, Borislav Petkov wrote:
> On Thu, Jun 02, 2016 at 09:58:30AM +0200, Borislav Petkov wrote:
> > Ha, very nice! Let me try it.
> 
> Yap, much better than opencoding on_each_cpu_mask() :-)
> 
> ---
> From: Borislav Petkov <bp@...e.de>
> Date: Wed, 1 Jun 2016 11:36:13 +0200
> Subject: [PATCH] hwmon: (fam15h_power) Disable preemption when reading
>  registers
> 
> We need to read a bunch of registers on each compute unit and possibly
> on the current CPU too. Disable preemption around it. Otherwise, you
> get:
> 
>   BUG: using smp_processor_id() in preemptible [00000000] code: systemd-udevd/327
>   caller is read_registers+0x6a/0x110 [fam15h_power]
>   CPU: 3 PID: 327 Comm: systemd-udevd Not tainted 4.7.0-rc1+ #4
>   Hardware name: HP HP EliteBook 745 G3/807E, BIOS N73 Ver. 01.08 01/28/2016
>   ...
> 
> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Borislav Petkov <bp@...e.de>
> Cc: Rui Huang <ray.huang@....com>
> Cc: Sherry Hurwitz <sherry.hurwitz@....com>
> Cc: Guenter Roeck <linux@...ck-us.net>
> Fixes: fa7943449943 ("hwmon: (fam15h_power) Add compute unit accumulated power")

I like this version. Applied, though it would be nice to get a Tested-by: or
Acked-by: from someone at AMD. I'll hold back until early next week before
sending it to Linus.

Thanks,
Guenter