linux-kernel - Re: [PATCH v3 5/7] gpio: Add GPIO Aggregator/Repeater driver

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Date:   Thu, 9 Jan 2020 14:49:56 +0100
From:   Eugeniu Rosca <erosca@...adit-jv.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
CC:     Eugeniu Rosca <roscaeugeniu@...il.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Jonathan Corbet <corbet@....net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Harish Jenny K N <harish_kandiga@...tor.com>,
        Eugeniu Rosca <erosca@...adit-jv.com>,
        Alexander Graf <graf@...zon.com>,
        Peter Maydell <peter.maydell@...aro.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Phil Reid <preid@...ctromag.com.au>,
        Marc Zyngier <marc.zyngier@....com>,
        Christoffer Dall <christoffer.dall@....com>,
        Magnus Damm <magnus.damm@...il.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        QEMU Developers <qemu-devel@...gnu.org>
Subject: Re: [PATCH v3 5/7] gpio: Add GPIO Aggregator/Repeater driver

Hi Geert,

On Thu, Jan 09, 2020 at 02:35:10PM +0100, Geert Uytterhoeven wrote:
> On Tue, Dec 3, 2019 at 11:51 AM Eugeniu Rosca <roscaeugeniu@...il.com> wrote:
> >
> > FWIW/FTR, doing some blind creation and deletion of gpio aggregator
> > chips [1] on R-Car H3ULCB overnight, kmemleak reported once [2]. Not
> > sure this is something 100% reproducible.
> >
> > [1] while true; do \
> >    echo e6055400.gpio 12,13 > /sys/bus/platform/drivers/gpio-aggregator/new_device; \
> >    echo gpio-aggregator.0 > /sys/bus/platform/drivers/gpio-aggregator/delete_device; \
> >    done
> >
> > [2] unreferenced object 0xffff0006d2c2e000 (size 128):
> >   comm "kworker/3:1", pid 55, jiffies 4294676978 (age 38546.676s)
> >   hex dump (first 32 bytes):
> >     00 d9 d2 d3 06 00 ff ff 0c 00 e0 0f ff ff ff ff  ................
> >     01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> >   backtrace:
> >     [<00000000a8e18c13>] slab_post_alloc_hook+0x8c/0x94
> >     [<000000006f419a4f>] __kmalloc+0x170/0x218
> >     [<0000000060d185ea>] kobj_map+0x78/0x1c0
> >     [<00000000c96645f3>] cdev_add+0x68/0x94
> >     [<00000000a7a5a8ac>] cdev_device_add+0x74/0x90
> >     [<00000000497871d3>] gpiochip_setup_dev+0x84/0x1f0
> >     [<00000000b993f95f>] gpiochip_add_data_with_key+0xbcc/0x11f0
> >     [<00000000fd728c0e>] devm_gpiochip_add_data+0x60/0xa8
> >     [<00000000442e34c1>] gpio_aggregator_probe+0x210/0x3c8
> >     [<00000000076e13fb>] platform_drv_probe+0x70/0xe4
> >     [<00000000de84b58b>] really_probe+0x2d8/0x434
> >     [<00000000c95c9784>] driver_probe_device+0x15c/0x16c
> >     [<00000000afb7dd4f>] __device_attach_driver+0xdc/0x120
> >     [<00000000efa40cae>] bus_for_each_drv+0x12c/0x154
> >     [<00000000c149acef>] __device_attach+0x148/0x1e0
> >     [<00000000a74fd158>] device_initial_probe+0x24/0x30
> 
> This is the allocation of the GPIO character device, which is allocated
> in response to the creation of the GPIO chip, from .probe().
> As that is done using devm_gpiochip_add_data(), the chardev should be
> deallocated automatically by devm_gpio_chip_release() when
> platform_device_unregister() is called.
> 
> Weird...

It might have been a false positive. Kmemleak is not w/o flaws.
I will retest and report later. In any case, it does not look
severe to me.

-- 
Best Regards,
Eugeniu