(subset) [PATCH] drm/vc4: drop all currently held locks if deadlock happens

[Maxime Ripard]

On Thu, 29 Dec 2022 16:46:38 -0300, Maíra Canal wrote:
> If vc4_hdmi_reset_link() returns -EDEADLK, it means that a deadlock
> happened in the locking context. This situation should be addressed by
> dropping all currently held locks and block until the contended lock
> becomes available. Currently, vc4 is not dealing with the deadlock
> properly, producing the following output when PROVE_LOCKING is enabled:
> 
> [  825.612809] ------------[ cut here ]------------
> [  825.612852] WARNING: CPU: 1 PID: 116 at drivers/gpu/drm/drm_modeset_lock.c:276 drm_modeset_drop_locks+0x60/0x68 [drm]
> [  825.613458] Modules linked in: 8021q mrp garp stp llc
> raspberrypi_cpufreq brcmfmac brcmutil crct10dif_ce hci_uart cfg80211
> btqca btbcm bluetooth vc4 raspberrypi_hwmon snd_soc_hdmi_codec cec
> clk_raspberrypi ecdh_generic drm_display_helper ecc rfkill
> drm_dma_helper drm_kms_helper pwm_bcm2835 bcm2835_thermal bcm2835_rng
> rng_core i2c_bcm2835 drm fuse ip_tables x_tables ipv6
> [  825.613735] CPU: 1 PID: 116 Comm: kworker/1:2 Tainted: G        W 6.1.0-rc6-01399-g941aae326315 #3
> [  825.613759] Hardware name: Raspberry Pi 3 Model B Rev 1.2 (DT)
> [  825.613777] Workqueue: events output_poll_execute [drm_kms_helper]
> [  825.614038] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [  825.614063] pc : drm_modeset_drop_locks+0x60/0x68 [drm]
> [  825.614603] lr : drm_helper_probe_detect+0x120/0x1b4 [drm_kms_helper]
> [  825.614829] sp : ffff800008313bf0
> [  825.614844] x29: ffff800008313bf0 x28: ffffcd7778b8b000 x27: 0000000000000000
> [  825.614883] x26: 0000000000000001 x25: 0000000000000001 x24: ffff677cc35c2758
> [  825.614920] x23: ffffcd7707d01430 x22: ffffcd7707c3edc7 x21: 0000000000000001
> [  825.614958] x20: 0000000000000000 x19: ffff800008313c10 x18: 000000000000b6d3
> [  825.614995] x17: ffffcd777835e214 x16: ffffcd7777cef870 x15: fffff81000000000
> [  825.615033] x14: 0000000000000000 x13: 0000000000000099 x12: 0000000000000002
> [  825.615070] x11: 72917988020af800 x10: 72917988020af800 x9 : 72917988020af800
> [  825.615108] x8 : ffff677cc665e0a8 x7 : d00a8c180000110c x6 : ffffcd77774c0054
> [  825.615145] x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000
> [  825.615181] x2 : ffff677cc55e1880 x1 : ffffcd7777cef8ec x0 : ffff800008313c10
> [  825.615219] Call trace:
> [  825.615232]  drm_modeset_drop_locks+0x60/0x68 [drm]
> [  825.615773]  drm_helper_probe_detect+0x120/0x1b4 [drm_kms_helper]
> [  825.616003]  output_poll_execute+0xe4/0x224 [drm_kms_helper]
> [  825.616233]  process_one_work+0x2b4/0x618
> [  825.616264]  worker_thread+0x24c/0x464
> [  825.616288]  kthread+0xec/0x110
> [  825.616310]  ret_from_fork+0x10/0x20
> [  825.616335] irq event stamp: 7634
> [  825.616349] hardirqs last  enabled at (7633): [<ffffcd777831ee90>] _raw_spin_unlock_irq+0x3c/0x78
> [  825.616384] hardirqs last disabled at (7634): [<ffffcd7778315a78>] __schedule+0x134/0x9f0
> [  825.616411] softirqs last  enabled at (7630): [<ffffcd7707aacea0>] local_bh_enable+0x4/0x30 [ipv6]
> [  825.617019] softirqs last disabled at (7618): [<ffffcd7707aace70>] local_bh_disable+0x4/0x30 [ipv6]
> [  825.617586] ---[ end trace 0000000000000000 ]---
> 
> [...]

Applied to drm/drm-misc (drm-misc-next).

Thanks!
Maxime