Re: Calling irq_set_irq_wake() from .set_irq_wake()?

[Geert Uytterhoeven]

On Fri, Jun 5, 2015 at 11:47 AM, Grygorii Strashko
<grygorii.strashko@xxxxxx> wrote:
> On 06/05/2015 05:35 AM, Roger Quadros wrote:
>> On Wed, 3 Jun 2015 22:52:47 +0300
>> Grygorii Strashko <grygorii.strashko@xxxxxx> wrote:
>>> On 05/19/2015 12:38 PM, Geert Uytterhoeven wrote:
>>>> On Mon, May 18, 2015 at 4:52 PM, Grygorii.Strashko@xxxxxxxxxx
>>>> <grygorii.strashko@xxxxxxxxxx> wrote:
>>>>> On 05/18/2015 05:31 PM, Thomas Gleixner wrote:
>>>>>> On Sun, 17 May 2015, Geert Uytterhoeven wrote:
>>>>>>>>>> At least the recursive locking message no longer appears after the revert.
>>>>>>>>>>
>>>>>>>>>> [   30.591905] PM: Syncing filesystems ... done.
>>>>>>>>>> [   30.623060] Freezing user space processes ... (elapsed 0.003 seconds) done.
>>>>>>>>>> [   30.634470] Freezing remaining freezable tasks ... (elapsed 0.002 seconds) done.
>>>>>>>>>> [   30.658288] sd 0:0:0:0: [sda] Synchronizing SCSI cache
>>>>>>>>>> [   30.663678]
>>>>>>>>>> [   30.663681] =============================================
>>>>>>>>>> [   30.663683] [ INFO: possible recursive locking detected ]
>>>>>>>>>> [   30.663688] 4.1.0-rc3 #1115 Not tainted
>>>>>>>>>> [   30.663693] ---------------------------------------------
>>>>>>>>>> [   30.663697] suspend.sh/2319 is trying to acquire lock:
>>>>>>>>>> [   30.663719]  (class){......}, at: [<c0096ebc>] __irq_get_desc_lock+0x48/0x88
>>>>>>>>>> [   30.663722]
>>>>>>>>>> [   30.663722] but task is already holding lock:
>>>>>>>>>> [   30.663734]  (class){......}, at: [<c0096ebc>] __irq_get_desc_lock+0x48/0x88
>>>>>>>>>
>>>>>>>>> Does this mean .set_irq_wake() cannot call irq_set_irq_wake()?
>>>>>>
>>>>>> It can call it, if it's guaranteed that this wont deadlock.
>>>>>>
>>>>>> To tell lockdep that you sure about that, you need to set a different
>>>>>> lock class for the child interrupts. irq_set_lockdep_class() is what
>>>>>> you want to use here.
>>>>>
>>>>> Hm. Seems we already have corresponding call in gpiochip_irq_map:
>>>>>
>>>>>    static int gpiochip_irq_map(struct irq_domain *d, unsigned int irq,
>>>>>                               irq_hw_number_t hwirq)
>>>>> {
>>>>>           struct gpio_chip *chip = d->host_data;
>>>>>
>>>>>           irq_set_chip_data(irq, chip);
>>>>>           irq_set_lockdep_class(irq, &gpiochip_irq_lock_class);
>>>>> ^^^^
>>>>
>>>> That piece of code sets the lockdep class of the gpiochip's interrupts, not
>>>> the parent interrupt.
>>>>
>>>> Found out the hard way by adding some debug code ;-)
>>> [..]
>>>>
>>>> However, I cannot reproduce the problem on sh73a0/kzm9g with
>>>> s2ram on a current tree (renesas-drivers-2015-05-19-v4.1-rc4 from
>>>> (https://git.kernel.org/cgit/linux/kernel/git/geert/renesas-drivers.git), using
>>>>
>>>> CONFIG_LOCKDEP_SUPPORT=y
>>>> CONFIG_LOCKDEP=y
>>>> CONFIG_DEBUG_LOCKDEP=y
>>>> CONFIG_PROVE_LOCKING=y
>>>>
>>>> Wake-up from gpio-keys works fine, no scary messages.
>>>>
>>>>> commit e45d1c80c0eee88e82751461e9cac49d9ed287bc
>>>>> Author: Linus Walleij <linus.walleij@xxxxxxxxxx>
>>>>> Date:   Tue Apr 22 14:01:46 2014 +0200
>>>>>
>>>>>       gpio: put GPIO IRQs into their own lock clas
>>>>>
>>>>> added in Kernel v3.16
>>>>>
>>>>> Roger, can you confirm that you've observed this issue with latest kernel, pls?
>>>>
>>>> Yes please. Thanks!
>>
>> Issue is reproducible on v4.1-rc6
>>
>>>
>>> Unfortunately, I was able to reproduce it, but have no clue how to fix it gracefully.
>>> lockdep_set_class_and_subclass(..,gpio_chip->base)?
>>>
>>> HW configuration which generates lockdep warning:
>>>
>>> [SOC GPIO bankA.gpioX] <- irq - [pcf875x.gpioY] <- irq - DevZ.enable_irq_wake(pcf_gpioY_irq);
>>>
>>> There stacked GPIO chips, but gpiolib uses only one lockdep class for all GPIOirqchips -
>>> - gpiochip_irq_lock_class.
>>
>> If this is a gpiolib core issue are we (dra7-evm) the only stacked GPIO users facing
>> this problem?
>>
>> Linus/Alexandre/Geert,
>>
>> Please advise what can be done for v4.1. The warning is annoying for dra7-evm users.
>> Should we temporarily revert the patch even though it is correct and add it back when the
>> gpiolib core issue is fixed?
>
> No. Pls. don't do that. See https://lkml.org/lkml/2015/6/3/965

I'm about to leave for a business trip to Japan. I will give it a try when I'm
back home.

> Simple revert is not good solution.
>
> Probably we need to allow GPIO drivers to specify own lockdep class somehow.

Indeed.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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