rcar-du/vsp1: possible recursive locking detected

[Kieran Bingham <kieran.bingham@ideasonboard.com>]

Observing this on linux-media/master branch, while running a simple
kmstest with dual outputs (HDMI, VGA)


Just reporting for the moment. We'll have to look at bisecting to see if
it was introduced recently.


[   31.644076] ============================================
[   31.649412] WARNING: possible recursive locking detected
[   31.654752] 4.18.0-rc2-arm64-renesas-12862-g666e994aa227 #25 Not tainted
[   31.661483] --------------------------------------------
[   31.666818] kmstest/986 is trying to acquire lock:
[   31.671631] 000000008bb5ef8e (&vsp1->drm->lock){+.+.}, at:
vsp1_du_setup_lif+0x90/0x438
[   31.679693]
[   31.679693] but task is already holding lock:
[   31.685551] 00000000ef2edc5c (&vsp1->drm->lock){+.+.}, at:
vsp1_du_atomic_begin+0x1c/0x28
[   31.693775]
[   31.693775] other info that might help us debug this:
[   31.700331]  Possible unsafe locking scenario:
[   31.700331]
[   31.706276]        CPU0
[   31.708731]        ----
[   31.711185]   lock(&vsp1->drm->lock);
[   31.714864]   lock(&vsp1->drm->lock);
[   31.718543]
[   31.718543]  *** DEADLOCK ***
[   31.718543]
[   31.724489]  May be due to missing lock nesting notation
[   31.724489]
[   31.731308] 3 locks held by kmstest/986:
[   31.735246]  #0: 0000000073af26f9 (crtc_ww_class_acquire){+.+.}, at:
drm_mode_atomic_ioctl+0xa0/0xa50
[   31.744523]  #1: 000000007a933c3a (crtc_ww_class_mutex){+.+.}, at:
drm_modeset_lock+0x64/0x118
[   31.753184]  #2: 00000000ef2edc5c (&vsp1->drm->lock){+.+.}, at:
vsp1_du_atomic_begin+0x1c/0x28
[   31.761844]
[   31.761844] stack backtrace:
[   31.766223] CPU: 1 PID: 986 Comm: kmstest Not tainted
4.18.0-rc2-arm64-renesas-12862-g666e994aa227 #25
[   31.775571] Hardware name: Renesas Salvator-X 2nd version board based
on r8a7795 ES2.0+ (DT)
[   31.784047] Call trace:
[   31.786509]  dump_backtrace+0x0/0x1c8
[   31.790187]  show_stack+0x14/0x20
[   31.793521]  dump_stack+0xbc/0xf4
[   31.796853]  __lock_acquire+0x964/0x1888
[   31.800792]  lock_acquire+0x48/0x64
[   31.804297]  __mutex_lock+0x70/0x838
[   31.807887]  mutex_lock_nested+0x1c/0x28
[   31.811826]  vsp1_du_setup_lif+0x90/0x438
[   31.815856]  rcar_du_vsp_enable+0x108/0x138
[   31.820057]  rcar_du_crtc_setup+0x3d8/0x548
[   31.824258]  rcar_du_crtc_atomic_begin+0x5c/0x70
[   31.828899]  drm_atomic_helper_commit_planes+0x70/0x208
[   31.834147]  rcar_du_atomic_commit_tail+0x30/0x68
[   31.838871]  commit_tail+0x44/0x78
[   31.842287]  drm_atomic_helper_commit+0xe8/0x160
[   31.846925]  drm_atomic_commit+0x48/0x58
[   31.850865]  drm_mode_atomic_ioctl+0x850/0xa50
[   31.855328]  drm_ioctl_kernel+0x88/0x108
[   31.859267]  drm_ioctl+0x1b8/0x400
[   31.862686]  do_vfs_ioctl+0xb8/0xa20
[   31.866276]  ksys_ioctl+0x44/0x90
[   31.869605]  sys_ioctl+0xc/0x18
[   31.872759]  el0_svc_naked+0x30/0x34

-- 
Regards
--
Kieran