linux-kernel - Re: [RFC PATCH V2 5/8] irqchip/gic: Return an error if GIC initialisation fails

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Date:	Fri, 18 Dec 2015 10:24:16 +0000
From:	Jon Hunter <jonathanh@...dia.com>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Marc Zyngier <marc.zyngier@....com>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Kevin Hilman <khilman@...nel.org>,
	"Geert Uytterhoeven" <geert@...ux-m68k.org>,
	Grygorii Strashko <grygorii.strashko@...com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	"Soren Brinkmann" <soren.brinkmann@...inx.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [RFC PATCH V2 5/8] irqchip/gic: Return an error if GIC
 initialisation fails


On 17/12/15 13:26, Linus Walleij wrote:
> On Thu, Dec 17, 2015 at 11:48 AM, Jon Hunter <jonathanh@...dia.com> wrote:
> 
>> If the GIC initialisation fails, then currently we do not return an error
>> or clean-up afterwards. Although for root controllers, this failure may be
>> fatal anyway, for secondary controllers, it may not be fatal and so return
>> an error on failure and clean-up.
>>
>> Also for non-banked GIC controllers, make sure that we free any memory
>> allocated if we fail to initialise the IRQ domain.
>>
>> Signed-off-by: Jon Hunter <jonathanh@...dia.com>
> (...)
> 
> Almost perfect but...
> 
>> +err:
>> +       if (IS_ENABLED(CONFIG_GIC_NON_BANKED) && percpu_offset) {
>> +               free_percpu(gic->dist_base.percpu_base);
>> +               free_percpu(gic->cpu_base.percpu_base);
> 
> What if the first map worked but not the second?
> 
> Should it be:
> 
> if (gic->dist_base.percpu_base)
>    free_percpu(gic->dist_base.percpu_base);
> if (gic->cpu_base.percpu_base)
>    free_percpu(gic->cpu_base.percpu_base);
> 
> ?

Yes this is a bit lazy, but the first thing free_percpu() checks if the
pointer is NULL and simply returns.

If you look at the current code in __gic_init_bases(), if one of the two
fail, we still try to free both. I did not like this, but when I looked
at it, I could see that is does work. Happy to change it though.

Cheers
Jon


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