Re: [PATCH] phylib: fix device deletion order in mdiobus_unregister()

[Mark Langsdorf]

On 09/01/2015 08:36 AM, Mark Salter wrote:
> commit 8b63ec1837fa ("phylib: Make PHYs children of their MDIO bus, not
> the bus' parent.") uncovered a problem in mdiobus_unregister() which
> leads to this warning when I reboot an APM Mustang (arm64) platform:
>
>    WARNING: CPU: 7 PID: 4239 at fs/sysfs/group.c:224 sysfs_remove_group+0xa0/0xa4()
>    sysfs group fffffe0000e07a10 not found for kobject 'xgene-mii-eth0:03'
>    ...
>    CPU: 7 PID: 4239 Comm: reboot Tainted: G            E   4.2.0-0.18.el7.test15.aarch64 #1
>    Hardware name: AppliedMicro Mustang/Mustang, BIOS 1.1.0 Aug 26 2015
>    Call Trace:
>    [<fffffe000009739c>] dump_backtrace+0x0/0x170
>    [<fffffe000009752c>] show_stack+0x20/0x2c
>    [<fffffe00007436f0>] dump_stack+0x78/0x9c
>    [<fffffe00000c2cb4>] warn_slowpath_common+0xa0/0xd8
>    [<fffffe00000c2d60>] warn_slowpath_fmt+0x74/0x88
>    [<fffffe0000293d3c>] sysfs_remove_group+0x9c/0xa4
>    [<fffffe00004a8bac>] dpm_sysfs_remove+0x5c/0x70
>    [<fffffe000049b388>] device_del+0x44/0x208
>    [<fffffe000049b578>] device_unregister+0x2c/0x7c
>    [<fffffe000050dc68>] mdiobus_unregister+0x48/0x94
>    [<fffffe000052afd0>] xgene_enet_mdio_remove+0x28/0x44
>    [<fffffe000052d3f0>] xgene_enet_remove+0xd0/0xd8
>    [<fffffe000052d424>] xgene_enet_shutdown+0x2c/0x3c
>    [<fffffe00004a204c>] platform_drv_shutdown+0x24/0x40
>    [<fffffe000049d4f4>] device_shutdown+0xf0/0x1b4
>    [<fffffe00000e31ec>] kernel_restart_prepare+0x40/0x4c
>    [<fffffe00000e32f8>] kernel_restart+0x1c/0x80
>    [<fffffe00000e3670>] SyS_reboot+0x17c/0x250
>
> The problem is that mdiobus_unregister() deletes the bus device before
> unregistering the phy devices on the bus. This wasn't a problem before
> because the phys were not children of the bus:
>
>    /sys/devices/platform/APMC0D05:00/net/eth0/xgene-mii-eth0:03
>    /sys/devices/platform/APMC0D05:00/net/eth0/xgene-mii-eth0
>
> But now that they are:
>
>    /sys/devices/platform/APMC0D05:00/net/eth0/xgene-mii-eth0/xgene-mii-eth0:03
>
> when mdiobus_unregister deletes the bus device, the phy subdirs are
> removed from sysfs also. So when the phys are unregistered afterward,
> we get the warning. This patch changes the order so that phys are
> unregistered before the bus device is deleted.
>
> Signed-off-by: Mark Salter <msalter@xxxxxxxxxx>
> ---

Tested-by: Mark Langsdorf <mlangsdo@xxxxxxxxxx>

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