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Re: [PATCH] regulator: Add lockdep asserts to help detecting locking misuse

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  Re: [PATCH] regulator: Add lockdep asserts to help detecting locking misuse Geert Uytterhoeven <geert@linux-m68k.org> - 2015-08-19 15:10 +0200
    Re: [PATCH] regulator: Add lockdep asserts to help detecting locking  misuse Mark Brown <broonie@kernel.org> - 2015-08-19 18:30 +0200
    Re: [PATCH] regulator: Add lockdep asserts to help detecting locking  misuse Krzysztof Kozlowski <k.kozlowski@samsung.com> - 2015-08-20 02:10 +0200

#1209824 — Re: [PATCH] regulator: Add lockdep asserts to help detecting locking misuse

Hi Krzysztof,

On Wed, Jun 10, 2015 at 8:23 AM, Krzysztof Kozlowski
<k.kozlowski@samsung.com> wrote:
> Add lockdep_assert_held_once() to functions explicitly mentioning that
> rdev or regulator_list mutex must be held. Using WARN_ONCE shouldn't
> pollute the dmesg to much.
>
> The patch (if CONFIG_LOCKDEP enabled) will show warnings in certain
> regulators calling regulator_notifier_call_chain() without rdev->mutex
> held.
>
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
>
> ---
>
> Warnings for missing locks when calling regulator_notifier_call_chain()
> should appear on many regulators except wm8350-regulator.c, e.g.:
> da9055-regulator.c, da9062-regulator.c, da9063-regulator.c,
> da9211-regulator.c, wm831x-dcdc.c and few more.
>
> The question is whether the lock during that call should be held?

That was a (so far, not counting the "Applied, thanks!") unanswered question?

For the first time ever, I got:

        drivers/regulator/core.c:3480 regulator_notifier_call_chain+0x54/0x80()

due to da9210_irq_handler() not taking the mutex.

Drivers calling regulator_notifier_call_chain() from a threaded interrupt
handler should be OK calling mutex_lock().

Does anyone have plans to fix all affected drivers?

Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

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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#1209938 — Re: [PATCH] regulator: Add lockdep asserts to help detecting locking misuse

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On Wed, Aug 19, 2015 at 03:08:34PM +0200, Geert Uytterhoeven wrote:

> Drivers calling regulator_notifier_call_chain() from a threaded interrupt
> handler should be OK calling mutex_lock().

> Does anyone have plans to fix all affected drivers?

I'm not aware of anyone who's shown an interest.

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#1210092 — Re: [PATCH] regulator: Add lockdep asserts to help detecting locking misuse

On 19.08.2015 22:08, Geert Uytterhoeven wrote:
> Hi Krzysztof,
> 
> On Wed, Jun 10, 2015 at 8:23 AM, Krzysztof Kozlowski
> <k.kozlowski@samsung.com> wrote:
>> Add lockdep_assert_held_once() to functions explicitly mentioning that
>> rdev or regulator_list mutex must be held. Using WARN_ONCE shouldn't
>> pollute the dmesg to much.
>>
>> The patch (if CONFIG_LOCKDEP enabled) will show warnings in certain
>> regulators calling regulator_notifier_call_chain() without rdev->mutex
>> held.
>>
>> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
>>
>> ---
>>
>> Warnings for missing locks when calling regulator_notifier_call_chain()
>> should appear on many regulators except wm8350-regulator.c, e.g.:
>> da9055-regulator.c, da9062-regulator.c, da9063-regulator.c,
>> da9211-regulator.c, wm831x-dcdc.c and few more.
>>
>> The question is whether the lock during that call should be held?
> 
> That was a (so far, not counting the "Applied, thanks!") unanswered question?
> 
> For the first time ever, I got:
> 
>         drivers/regulator/core.c:3480 regulator_notifier_call_chain+0x54/0x80()
> 
> due to da9210_irq_handler() not taking the mutex.
> 
> Drivers calling regulator_notifier_call_chain() from a threaded interrupt
> handler should be OK calling mutex_lock().
> 
> Does anyone have plans to fix all affected drivers?

Question is still unanswered. I don't have plans to fix the drivers
because I don't have necessary hardware. Blindly fixing such minor issue
could do more harm than good. I just polluted the dmesg with WARN hoping
that this will wake up someone :) .

Best regards,
Krzysztof
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