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

[Grygorii Strashko <grygorii.strashko@ti.com>]

Hi Geert,

On 05/19/2015 12:38 PM, Geert Uytterhoeven wrote:
> On Mon, May 18, 2015 at 4:52 PM, Grygorii.Strashko@linaro.org
> <grygorii.strashko@linaro.org> 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@linaro.org>
>> 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!

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.


> 
>>>>>> Many GPIO drivers do that, as they need to propagate wake-up state to the
>>>>>> parent interrupt controller?
>>>>>
>>>>> As I remember, there was similar problem, so I found corresponding patch (just FYI)
>>>>>
>>>>> ab2b926 mfd: Fix twl6030 lockdep recursion warning on setting wake IRQs
>>>>>
>>>>> Not sure such kind of solution is the best choice (
>>>>
>>>> That looks like a convoluted solution...
>>>

regards,
-grygorii