Re: [PATCH] software node: balance refcount for managed sw nodes

Heikki Krogerus
2021-09-14T14:00:11Z

On Fri, Jul 16, 2021 at 01:16:02PM +0300, laurentiu.tudor@nxp.com wrote:
> From: Laurentiu Tudor <laurentiu.tudor@nxp.com>
>
> software_node_notify(), on KOBJ_REMOVE drops the refcount twice on managed
> software nodes, thus leading to underflow errors. Balance the refcount by
> bumping it in the device_create_managed_software_node() function.
>
> The error [1] was encountered after adding a .shutdown() op to our
> fsl-mc-bus driver.
>
> [1]
> pc : refcount_warn_saturate+0xf8/0x150
> lr : refcount_warn_saturate+0xf8/0x150
> sp : ffff80001009b920
> x29: ffff80001009b920 x28: ffff1a2420318000 x27: 0000000000000000
> x26: ffffccac15e7a038 x25: 0000000000000008 x24: ffffccac168e0030
> x23: ffff1a2428a82000 x22: 0000000000080000 x21: ffff1a24287b5000
> x20: 0000000000000001 x19: ffff1a24261f4400 x18: ffffffffffffffff
> x17: 6f72645f726f7272 x16: 0000000000000000 x15: ffff80009009b607
> x14: 0000000000000000 x13: ffffccac16602670 x12: 0000000000000a17
> x11: 000000000000035d x10: ffffccac16602670 x9 : ffffccac16602670
> x8 : 00000000ffffefff x7 : ffffccac1665a670 x6 : ffffccac1665a670
> x5 : 0000000000000000 x4 : 0000000000000000 x3 : 00000000ffffffff
> x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff1a2420318000
> Call trace:
> refcount_warn_saturate+0xf8/0x150
> kobject_put+0x10c/0x120
> software_node_notify+0xd8/0x140
> device_platform_notify+0x4c/0xb4
> device_del+0x188/0x424
> fsl_mc_device_remove+0x2c/0x4c
> rebofind sp.c__fsl_mc_device_remove+0x14/0x2c
> device_for_each_child+0x5c/0xac
> dprc_remove+0x9c/0xc0
> fsl_mc_driver_remove+0x28/0x64
> __device_release_driver+0x188/0x22c
> device_release_driver+0x30/0x50
> bus_remove_device+0x128/0x134
> device_del+0x16c/0x424
> fsl_mc_bus_remove+0x8c/0x114
> fsl_mc_bus_shutdown+0x14/0x20
> platform_shutdown+0x28/0x40
> device_shutdown+0x15c/0x330
> __do_sys_reboot+0x218/0x2a0
> __arm64_sys_reboot+0x28/0x34
> invoke_syscall+0x48/0x114
> el0_svc_common+0x40/0xdc
> do_el0_svc+0x2c/0x94
> el0_svc+0x2c/0x54
> el0t_64_sync_handler+0xa8/0x12c
> el0t_64_sync+0x198/0x19c
> ---[ end trace 32eb1c71c7d86821 ]---
>
> Reported-by: Jon Nettleton <jon@solid-run.com>
> Suggested-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>

FWIW:

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
> Changes since RFC:
> - use software_node_notify(KOBJ_ADD) instead of directly bumping
> refcount (Heikki)
>
> drivers/base/swnode.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
> index d1f1a8240120..bdb50a06c82a 100644
> --- a/drivers/base/swnode.c
> +++ b/drivers/base/swnode.c
> @@ -1113,6 +1113,9 @@ int device_create_managed_software_node(struct device *dev,
> to_swnode(fwnode)->managed = true;
> set_secondary_fwnode(dev, fwnode);
>
> + if (device_is_registered(dev))
> + software_node_notify(dev, KOBJ_ADD);
> +
> return 0;
> }
> EXPORT_SYMBOL_GPL(device_create_managed_software_node);
> --
> 2.17.1

thanks,

--
heikki