[PATCH v2] drm/i2c: tda998x: Fix lockdep warning about possible circular dependency
From: Liviu Dudau
Date: Thu Jul 20 2017 - 10:19:40 EST
When enabling lockdep debugging on Juno platform with HDLCD and TDA998x
I get the following warning from the system:
[ 25.990733] ======================================================
[ 25.998637] WARNING: possible circular locking dependency detected
[ 26.006531] 4.13.0-rc1-00284-g28c0a682ecbf-dirty #17 Not tainted
[ 26.014246] ------------------------------------------------------
[ 26.022142] kworker/1:2/140 is trying to acquire lock:
[ 26.029001] (&priv->audio_mutex){+.+.+.}, at: [<ffff000000d0319c>] tda998x_encoder_mode_set+0x12c/0x5a0 [tda998x]
[ 26.041100]
[ 26.041100] but task is already holding lock:
[ 26.050436] (crtc_ww_class_mutex){+.+.+.}, at: [<ffff000000eaefe4>] drm_modeset_lock+0x64/0xf8 [drm]
[ 26.061531]
[ 26.061531] which lock already depends on the new lock.
[ 26.061531]
[ 26.075063]
[ 26.075063] the existing dependency chain (in reverse order) is:
[ 26.086031]
[ 26.086031] -> #2 (crtc_ww_class_mutex){+.+.+.}:
[ 26.095657] __lock_acquire+0x18a0/0x19b8
[ 26.101918] lock_acquire+0xd0/0x2b0
[ 26.107731] __ww_mutex_lock.constprop.3+0x90/0xe78
[ 26.114817] ww_mutex_lock+0x54/0xe0
[ 26.120672] drm_modeset_lock+0x64/0xf8 [drm]
[ 26.127253] drm_helper_probe_single_connector_modes+0x7c/0x6b8 [drm_kms_helper]
[ 26.136829] tda998x_connector_fill_modes+0x44/0xa8 [tda998x]
[ 26.144797] drm_setup_crtcs+0x19c/0xba0 [drm_kms_helper]
[ 26.152429] drm_fb_helper_initial_config+0x70/0x440 [drm_kms_helper]
[ 26.161097] drm_fbdev_cma_init_with_funcs+0x94/0x168 [drm_kms_helper]
[ 26.169857] drm_fbdev_cma_init+0x38/0x50 [drm_kms_helper]
[ 26.177559] hdlcd_drm_bind+0x1f8/0x4a8 [hdlcd]
[ 26.184310] try_to_bring_up_master+0x180/0x1e0
[ 26.191043] component_master_add_with_match+0xb0/0x108
[ 26.198458] hdlcd_probe+0x58/0x80 [hdlcd]
[ 26.204735] platform_drv_probe+0x60/0xc0
[ 26.210913] driver_probe_device+0x23c/0x2e8
[ 26.217350] __driver_attach+0xd4/0xd8
[ 26.223256] bus_for_each_dev+0x5c/0xa8
[ 26.229232] driver_attach+0x30/0x40
[ 26.234917] bus_add_driver+0x1d8/0x248
[ 26.240831] driver_register+0x6c/0x118
[ 26.246715] __platform_driver_register+0x54/0x60
[ 26.253461] 0xffff000000e1b018
[ 26.258644] do_one_initcall+0x44/0x138
[ 26.264503] do_init_module+0x64/0x1d4
[ 26.270238] load_module+0x1f90/0x2590
[ 26.275957] SyS_finit_module+0xb0/0xc8
[ 26.281765] __sys_trace_return+0x0/0x4
[ 26.281767]
[ 26.281767] -> #1 (crtc_ww_class_acquire){+.+.+.}:
[ 26.281778] __lock_acquire+0x18a0/0x19b8
[ 26.281782] lock_acquire+0xd0/0x2b0
[ 26.281877] drm_modeset_acquire_init+0xa8/0xe0 [drm]
[ 26.281921] drm_helper_probe_single_connector_modes+0x48/0x6b8 [drm_kms_helper]
[ 26.281929] tda998x_connector_fill_modes+0x44/0xa8 [tda998x]
[ 26.281970] drm_setup_crtcs+0x19c/0xba0 [drm_kms_helper]
[ 26.282009] drm_fb_helper_initial_config+0x70/0x440 [drm_kms_helper]
[ 26.282049] drm_fbdev_cma_init_with_funcs+0x94/0x168 [drm_kms_helper]
[ 26.282088] drm_fbdev_cma_init+0x38/0x50 [drm_kms_helper]
[ 26.282095] hdlcd_drm_bind+0x1f8/0x4a8 [hdlcd]
[ 26.282099] try_to_bring_up_master+0x180/0x1e0
[ 26.282104] component_master_add_with_match+0xb0/0x108
[ 26.282110] hdlcd_probe+0x58/0x80 [hdlcd]
[ 26.282114] platform_drv_probe+0x60/0xc0
[ 26.282117] driver_probe_device+0x23c/0x2e8
[ 26.282121] __driver_attach+0xd4/0xd8
[ 26.282124] bus_for_each_dev+0x5c/0xa8
[ 26.282127] driver_attach+0x30/0x40
[ 26.282130] bus_add_driver+0x1d8/0x248
[ 26.282134] driver_register+0x6c/0x118
[ 26.282138] __platform_driver_register+0x54/0x60
[ 26.282141] 0xffff000000e1b018
[ 26.282145] do_one_initcall+0x44/0x138
[ 26.282149] do_init_module+0x64/0x1d4
[ 26.282152] load_module+0x1f90/0x2590
[ 26.282156] SyS_finit_module+0xb0/0xc8
[ 26.282159] __sys_trace_return+0x0/0x4
[ 26.282161]
[ 26.282161] -> #0 (&priv->audio_mutex){+.+.+.}:
[ 26.282172] print_circular_bug+0x80/0x2e0
[ 26.282176] __lock_acquire+0x15a8/0x19b8
[ 26.282180] lock_acquire+0xd0/0x2b0
[ 26.282184] __mutex_lock+0x78/0x8e0
[ 26.282188] mutex_lock_nested+0x3c/0x50
[ 26.282196] tda998x_encoder_mode_set+0x12c/0x5a0 [tda998x]
[ 26.282237] drm_atomic_helper_commit_modeset_disables+0x328/0x3a0 [drm_kms_helper]
[ 26.282251] malidp_atomic_commit_tail+0x44/0x6b0 [mali_dp]
[ 26.282292] commit_tail+0x4c/0x80 [drm_kms_helper]
[ 26.282333] drm_atomic_helper_commit+0xe8/0x180 [drm_kms_helper]
[ 26.282427] drm_atomic_commit+0x54/0x70 [drm]
[ 26.282467] restore_fbdev_mode_atomic+0x1f0/0x220 [drm_kms_helper]
[ 26.282507] restore_fbdev_mode+0x38/0x188 [drm_kms_helper]
[ 26.282547] drm_fb_helper_restore_fbdev_mode_unlocked+0x44/0xd0 [drm_kms_helper]
[ 26.282586] drm_fb_helper_set_par+0x34/0x80 [drm_kms_helper]
[ 26.282625] drm_fb_helper_hotplug_event.part.19+0x94/0xb0 [drm_kms_helper]
[ 26.282665] drm_fb_helper_hotplug_event+0x2c/0x48 [drm_kms_helper]
[ 26.282704] drm_fbdev_cma_hotplug_event+0x24/0x30 [drm_kms_helper]
[ 26.282716] malidp_output_poll_changed+0x24/0x30 [mali_dp]
[ 26.282757] drm_kms_helper_hotplug_event+0x34/0x40 [drm_kms_helper]
[ 26.282797] output_poll_execute+0x1a0/0x1f0 [drm_kms_helper]
[ 26.282803] process_one_work+0x280/0x790
[ 26.282808] worker_thread+0x48/0x450
[ 26.282812] kthread+0x138/0x140
[ 26.282815] ret_from_fork+0x10/0x40
[ 26.282817]
[ 26.282817] other info that might help us debug this:
[ 26.282817]
[ 26.282819] Chain exists of:
[ 26.282819] &priv->audio_mutex --> crtc_ww_class_acquire --> crtc_ww_class_mutex
[ 26.282819]
[ 26.282830] Possible unsafe locking scenario:
[ 26.282830]
[ 26.282832] CPU0 CPU1
[ 26.282834] ---- ----
[ 26.282835] lock(crtc_ww_class_mutex);
[ 26.282840] lock(crtc_ww_class_acquire);
[ 26.282845] lock(crtc_ww_class_mutex);
[ 26.282850] lock(&priv->audio_mutex);
[ 26.282854]
[ 26.282854] *** DEADLOCK ***
[ 26.282854]
[ 26.282858] 5 locks held by kworker/1:2/140:
[ 26.282859] #0: ("events"){.+.+.+}, at: [<ffff0000080f8500>] process_one_work+0x1d8/0x790
[ 26.282871] #1: ((&(&dev->mode_config.output_poll_work)->work)){+.+.+.}, at: [<ffff0000080f8500>] process_one_work+0x1d8/0x790
[ 26.282883] #2: (&helper->lock){+.+.+.}, at: [<ffff000000c0631c>] drm_fb_helper_restore_fbdev_mode_unlocked+0x3c/0xd0 [drm_kms_helper]
[ 26.282929] #3: (crtc_ww_class_acquire){+.+.+.}, at: [<ffff000000c02d80>] restore_fbdev_mode_atomic+0x38/0x220 [drm_kms_helper]
[ 26.282976] #4: (crtc_ww_class_mutex){+.+.+.}, at: [<ffff000000eaefe4>] drm_modeset_lock+0x64/0xf8 [drm]
[ 26.283077]
[ 26.283077] stack backtrace:
[ 26.283082] CPU: 1 PID: 140 Comm: kworker/1:2 Not tainted 4.13.0-rc1-00284-g28c0a682ecbf-dirty #17
[ 26.283084] Hardware name: ARM Juno development board (r0) (DT)
[ 26.283127] Workqueue: events output_poll_execute [drm_kms_helper]
[ 26.283131] Call trace:
[ 26.283137] [<ffff00000808a778>] dump_backtrace+0x0/0x268
[ 26.283142] [<ffff00000808aabc>] show_stack+0x24/0x30
[ 26.283146] [<ffff000008aa36a8>] dump_stack+0xbc/0xf4
[ 26.283151] [<ffff00000812f454>] print_circular_bug+0x1d4/0x2e0
[ 26.283155] [<ffff000008132480>] __lock_acquire+0x15a8/0x19b8
[ 26.283159] [<ffff000008133008>] lock_acquire+0xd0/0x2b0
[ 26.283163] [<ffff000008aba060>] __mutex_lock+0x78/0x8e0
[ 26.283168] [<ffff000008aba904>] mutex_lock_nested+0x3c/0x50
[ 26.283176] [<ffff000000d0319c>] tda998x_encoder_mode_set+0x12c/0x5a0 [tda998x]
[ 26.283217] [<ffff000000c00050>] drm_atomic_helper_commit_modeset_disables+0x328/0x3a0 [drm_kms_helper]
[ 26.283230] [<ffff000000f1bd0c>] malidp_atomic_commit_tail+0x44/0x6b0 [mali_dp]
[ 26.283271] [<ffff000000c0045c>] commit_tail+0x4c/0x80 [drm_kms_helper]
[ 26.283312] [<ffff000000c00630>] drm_atomic_helper_commit+0xe8/0x180 [drm_kms_helper]
[ 26.283406] [<ffff000000eb1604>] drm_atomic_commit+0x54/0x70 [drm]
[ 26.283447] [<ffff000000c02f38>] restore_fbdev_mode_atomic+0x1f0/0x220 [drm_kms_helper]
[ 26.283487] [<ffff000000c03cf0>] restore_fbdev_mode+0x38/0x188 [drm_kms_helper]
[ 26.283526] [<ffff000000c06324>] drm_fb_helper_restore_fbdev_mode_unlocked+0x44/0xd0 [drm_kms_helper]
[ 26.283566] [<ffff000000c0619c>] drm_fb_helper_set_par+0x34/0x80 [drm_kms_helper]
[ 26.283606] [<ffff000000c0627c>] drm_fb_helper_hotplug_event.part.19+0x94/0xb0 [drm_kms_helper]
[ 26.283645] [<ffff000000c062c4>] drm_fb_helper_hotplug_event+0x2c/0x48 [drm_kms_helper]
[ 26.283685] [<ffff000000c07124>] drm_fbdev_cma_hotplug_event+0x24/0x30 [drm_kms_helper]
[ 26.283697] [<ffff000000f1b44c>] malidp_output_poll_changed+0x24/0x30 [mali_dp]
[ 26.283738] [<ffff000000bf5264>] drm_kms_helper_hotplug_event+0x34/0x40 [drm_kms_helper]
[ 26.283779] [<ffff000000bf5480>] output_poll_execute+0x1a0/0x1f0 [drm_kms_helper]
[ 26.283784] [<ffff0000080f85a8>] process_one_work+0x280/0x790
[ 26.283788] [<ffff0000080f8b00>] worker_thread+0x48/0x450
[ 26.283792] [<ffff000008100430>] kthread+0x138/0x140
[ 26.283796] [<ffff000008083710>] ret_from_fork+0x10/0x40
This looks like it has been introduced by 'commit 02efac0fbfd5 ("drm/i2c:
tda998x: remove complexity from tda998x_audio_get_eld()")'.
Fix the warning by dropping the use of local audio_mutex and switch to
taking the modeset connection_mutex in tda998x_audio_get_eld() for
avoidance of race conditions with drm_helper_probe_single_connector_modes()
updating the ELD data.
v2: Change to taking the modeset connection_mutex rather than changing
the time when audio_mutex lock was taken, as suggested by Russell King.
Signed-off-by: Liviu Dudau <Liviu.Dudau@xxxxxxx>
Cc: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
Fixes: 02efac0fbfd5 ("drm/i2c: tda998x: remove complexity from tda998x_audio_get_eld()")
---
drivers/gpu/drm/i2c/tda998x_drv.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c b/drivers/gpu/drm/i2c/tda998x_drv.c
index d1e7ac540199..e34c3a032a7d 100644
--- a/drivers/gpu/drm/i2c/tda998x_drv.c
+++ b/drivers/gpu/drm/i2c/tda998x_drv.c
@@ -926,13 +926,26 @@ static int tda998x_audio_get_eld(struct device *dev, void *data,
uint8_t *buf, size_t len)
{
struct tda998x_priv *priv = dev_get_drvdata(dev);
+ struct drm_modeset_acquire_ctx ctx;
+ struct drm_device *drm_dev = priv->connector.dev;
+ int ret;
- mutex_lock(&priv->audio_mutex);
- memcpy(buf, priv->connector.eld,
- min(sizeof(priv->connector.eld), len));
- mutex_unlock(&priv->audio_mutex);
+ drm_modeset_acquire_init(&ctx, 0);
+retry:
+ ret = drm_modeset_lock(&drm_dev->mode_config.connection_mutex, &ctx);
+ if (!ret)
+ memcpy(buf, priv->connector.eld,
+ min(sizeof(priv->connector.eld), len));
- return 0;
+ if (ret == -EDEADLK) {
+ drm_modeset_backoff(&ctx);
+ goto retry;
+ }
+
+ drm_modeset_drop_locks(&ctx);
+ drm_modeset_acquire_fini(&ctx);
+
+ return ret;
}
static const struct hdmi_codec_ops audio_codec_ops = {
@@ -983,7 +996,6 @@ static int tda998x_connector_fill_modes(struct drm_connector *connector,
struct tda998x_priv *priv = conn_to_tda998x_priv(connector);
int ret;
- mutex_lock(&priv->audio_mutex);
ret = drm_helper_probe_single_connector_modes(connector, maxX, maxY);
if (connector->edid_blob_ptr) {
@@ -993,7 +1005,6 @@ static int tda998x_connector_fill_modes(struct drm_connector *connector,
} else {
priv->sink_has_audio = false;
}
- mutex_unlock(&priv->audio_mutex);
return ret;
}
--
2.13.2