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 [off-list ref] wrote:

quoted

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