Hi Eugeniu,
Thanks for your report, the issue is known and fixed in [1] which is in
the media-tree [2] on it's way to mainline.
1. d950fd992ef89f39 ("media: rcar-vin: Fix lockdep warning at stream on")
2. https://git.linuxtv.org/media_tree.git/
On 2019-04-05 16:17:18 +0200, Eugeniu Rosca wrote:
> Hi Niklas,
>
> jFYI/FWIW, checking the functionality of rcar-vin using the
> procedure/commands described in https://elinux.org/R-Car/Tests:rcar-vin
> on the recent Linux commit ea2cec24c8d429ee6f99040e4eb6c7ad627fe777, I
> consistently reproduce below lockdep splat [2] (full log and .config at
> https://gist.github.com/erosca/67a46451b3cb342fa59b558022278fff).
>
> Since the locking primitives of rvin_group_link_notify (popping up in
> the log) haven't suffered changes since v4.18-rc1 commit [1], I conclude
> this thread [0] might be an appropriate place for reporting the issue.
>
> Best regards,
> Eugeniu.
>
> [0] https://patchwork.kernel.org/patch/10341183/ [v14,29/33] rcar-vin: add link notify for Gen3
> [1] c0cc5aef31704c ("media: rcar-vin: add link notify for Gen3")
> [2] media-ctl -l "'rcar_csi2 feaa0000.csi2':1 -> 'VIN0 output':0 [1]"
>
> ======================================================
> WARNING: possible circular locking dependency detected
> 5.1.0-rc3+ #27 Tainted: G W
> ------------------------------------------------------
> media-ctl/2407 is trying to acquire lock:
> 00000000be992082 (&group->lock){+.+.}, at: rvin_group_link_notify+0xc4/0x4f4
>
> but task is already holding lock:
> 0000000064693a2a (&mdev->graph_mutex){+.+.}, at: media_device_ioctl+0x1f8/0x2b8
>
> which lock already depends on the new lock.
>
> the existing dependency chain (in reverse order) is:
>
> -> #2 (&mdev->graph_mutex){+.+.}:
> lock_acquire+0x144/0x39c
> __mutex_lock+0xe8/0xb54
> mutex_lock_nested+0x3c/0x4c
> media_device_register_entity+0x15c/0x308
> v4l2_device_register_subdev+0x1c8/0x288
> v4l2_async_match_notify+0x3c/0x200
> v4l2_async_notifier_try_all_subdevs+0xb8/0xc0
> __v4l2_async_notifier_register+0xac/0x214
> v4l2_async_notifier_register+0x68/0x80
> rcar_vin_probe+0x8d8/0xa0c
> platform_drv_probe+0x70/0xe4
> really_probe+0x2d8/0x3d8
> driver_probe_device+0x154/0x164
> device_driver_attach+0x98/0xa0
> __driver_attach+0xf0/0xf4
> bus_for_each_dev+0x114/0x13c
> driver_attach+0x38/0x44
> bus_add_driver+0x234/0x288
> driver_register+0x148/0x190
> __platform_driver_register+0x84/0x90
> rcar_vin_driver_init+0x20/0x28
> do_one_initcall+0x124/0x68c
> kernel_init_freeable+0xa5c/0xa60
> kernel_init+0x18/0x134
> ret_from_fork+0x10/0x18
>
> -> #1 (list_lock){+.+.}:
> lock_acquire+0x144/0x39c
> __mutex_lock+0xe8/0xb54
> mutex_lock_nested+0x3c/0x4c
> v4l2_async_notifier_add_subdev+0x3c/0xdc
> __v4l2_async_notifier_parse_fwnode_ep+0x240/0x2b8
> v4l2_async_notifier_parse_fwnode_endpoints_by_port+0x4c/0x60
> rcar_vin_probe+0x858/0xa0c
> platform_drv_probe+0x70/0xe4
> really_probe+0x2d8/0x3d8
> driver_probe_device+0x154/0x164
> device_driver_attach+0x98/0xa0
> __driver_attach+0xf0/0xf4
> bus_for_each_dev+0x114/0x13c
> driver_attach+0x38/0x44
> bus_add_driver+0x234/0x288
> driver_register+0x148/0x190
> __platform_driver_register+0x84/0x90
> rcar_vin_driver_init+0x20/0x28
> do_one_initcall+0x124/0x68c
> kernel_init_freeable+0xa5c/0xa60
> kernel_init+0x18/0x134
> ret_from_fork+0x10/0x18
>
> -> #0 (&group->lock){+.+.}:
> __lock_acquire+0x1c7c/0x1dd0
> lock_acquire+0x144/0x39c
> __mutex_lock+0xe8/0xb54
> mutex_lock_nested+0x3c/0x4c
> rvin_group_link_notify+0xc4/0x4f4
> __media_entity_setup_link+0x238/0x2f0
> media_device_setup_link+0x114/0x11c
> media_device_ioctl+0x21c/0x2b8
> __media_ioctl+0x78/0x84
> media_ioctl+0x58/0x68
> vfs_ioctl+0x68/0x78
> do_vfs_ioctl+0x134/0xbfc
> ksys_ioctl+0x68/0x98
> __arm64_sys_ioctl+0x4c/0x60
> el0_svc_common+0xd0/0x16c
> el0_svc_handler+0x94/0xa0
> el0_svc+0x8/0xc
>
> other info that might help us debug this:
>
> Chain exists of:
> &group->lock --> list_lock --> &mdev->graph_mutex
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(&mdev->graph_mutex);
> lock(list_lock);
> lock(&mdev->graph_mutex);
> lock(&group->lock);
>
> *** DEADLOCK ***
>
> 1 lock held by media-ctl/2407:
> #0: 0000000064693a2a (&mdev->graph_mutex){+.+.}, at: media_device_ioctl+0x1f8/0x2b8
>
> stack backtrace:
> CPU: 0 PID: 2407 Comm: media-ctl Tainted: G W 5.1.0-rc3+ #27
> Hardware name: Renesas Salvator-X board based on r8a7795 ES2.0+ (DT)
> Call trace:
> dump_backtrace+0x0/0x1c0
> show_stack+0x24/0x30
> dump_stack+0xcc/0x128
> print_circular_bug.isra.16+0x22c/0x364
> check_prev_add.constprop.25+0x35c/0x1098
> __lock_acquire+0x1c7c/0x1dd0
> lock_acquire+0x144/0x39c
> __mutex_lock+0xe8/0xb54
> mutex_lock_nested+0x3c/0x4c
> rvin_group_link_notify+0xc4/0x4f4
> __media_entity_setup_link+0x238/0x2f0
> media_device_setup_link+0x114/0x11c
> media_device_ioctl+0x21c/0x2b8
> __media_ioctl+0x78/0x84
> media_ioctl+0x58/0x68
> vfs_ioctl+0x68/0x78
> do_vfs_ioctl+0x134/0xbfc
> ksys_ioctl+0x68/0x98
> __arm64_sys_ioctl+0x4c/0x60
> el0_svc_common+0xd0/0x16c
> el0_svc_handler+0x94/0xa0
> el0_svc+0x8/0xc
--
Regards,
Niklas Söderlund
