linux-kernel - Re: lockdep: incorrect deadlock warning with two GPIO expanders

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Date:   Fri, 16 Sep 2016 13:14:33 +0200
From:   Bartosz Golaszewski <bgolaszewski@...libre.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Alexandre Courbot <gnurou@...il.com>,
        Ingo Molnar <mingo@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-gpio <linux-gpio@...r.kernel.org>
Subject: Re: lockdep: incorrect deadlock warning with two GPIO expanders

2016-09-16 12:56 GMT+02:00 Peter Zijlstra <peterz@...radead.org>:
> On Thu, Sep 15, 2016 at 03:39:22PM +0200, Peter Zijlstra wrote:
>
>> In any case, if this fails, we can always punt and simply count the
>> total number of instances of this driver on the system and go with that.
>
> One caveat with that approach is that if this is s module, someone doing
> rmmod, insmod a number of times gets tricky.

The whole thing is a bit more complicated - I'm trying to figure out
the code behind it, but the first expander has four parents whose
driver == pca953x, while the second has five of them. There is no
device name, but kobj->name corresponds with the i2c device
sub-directories on correct addresses and busses (1-0021 for the first
one and 4-0020 for the second on my board).

With both devices having pca953x parents I still can't tell one from
another. Still working on it.

Thanks,
Bartosz Golaszewski