On 09/04/2022 00:04, Kuogee Hsieh wrote:
There is possible circular locking dependency detected on event_mutex
(see below logs). This is due to set fail safe mode is done at
dp_panel_read_sink_caps() within event_mutex scope. To break this
possible circular locking, this patch move setting fail safe mode
out of event_mutex scope.
[ 23.958078] ======================================================
[ 23.964430] WARNING: possible circular locking dependency detected
[ 23.970777] 5.17.0-rc2-lockdep-00088-g05241de1f69e #148 Not tainted
[ 23.977219] ------------------------------------------------------
[ 23.983570] DrmThread/1574 is trying to acquire lock:
[ 23.988763] ffffff808423aab0 (&dp->event_mutex){+.+.}-{3:3}, at: msm_dp_displ ay_enable+0x58/0x164
[ 23.997895]
[ 23.997895] but task is already holding lock:
[ 24.003895] ffffff808420b280 (&kms->commit_lock[i]/1){+.+.}-{3:3}, at: lock_c rtcs+0x80/0x8c
[ 24.012495]
[ 24.012495] which lock already depends on the new lock.
[ 24.012495]
[ 24.020886]
[ 24.020886] the existing dependency chain (in reverse order) is:
[ 24.028570]
[ 24.028570] -> #5 (&kms->commit_lock[i]/1){+.+.}-{3:3}:
[ 24.035472] __mutex_lock+0xc8/0x384
[ 24.039695] mutex_lock_nested+0x54/0x74
[ 24.044272] lock_crtcs+0x80/0x8c
[ 24.048222] msm_atomic_commit_tail+0x1e8/0x3d0
[ 24.053413] commit_tail+0x7c/0xfc
[ 24.057452] drm_atomic_helper_commit+0x158/0x15c
[ 24.062826] drm_atomic_commit+0x60/0x74
[ 24.067403] drm_mode_atomic_ioctl+0x6b0/0x908
[ 24.072508] drm_ioctl_kernel+0xe8/0x168
[ 24.077086] drm_ioctl+0x320/0x370
[ 24.081123] drm_compat_ioctl+0x40/0xdc
[ 24.085602] __arm64_compat_sys_ioctl+0xe0/0x150
[ 24.090895] invoke_syscall+0x80/0x114
[ 24.095294] el0_svc_common.constprop.3+0xc4/0xf8
[ 24.100668] do_el0_svc_compat+0x2c/0x54
[ 24.105242] el0_svc_compat+0x4c/0xe4
[ 24.109548] el0t_32_sync_handler+0xc4/0xf4
[ 24.114381] el0t_32_sync+0x178
[ 24.118688]
[ 24.118688] -> #4 (&kms->commit_lock[i]){+.+.}-{3:3}:
[ 24.125408] __mutex_lock+0xc8/0x384
[ 24.129628] mutex_lock_nested+0x54/0x74
[ 24.134204] lock_crtcs+0x80/0x8c
[ 24.138155] msm_atomic_commit_tail+0x1e8/0x3d0
[ 24.143345] commit_tail+0x7c/0xfc
[ 24.147382] drm_atomic_helper_commit+0x158/0x15c
[ 24.152755] drm_atomic_commit+0x60/0x74
[ 24.157323] drm_atomic_helper_set_config+0x68/0x90
[ 24.162869] drm_mode_setcrtc+0x394/0x648
[ 24.167535] drm_ioctl_kernel+0xe8/0x168
[ 24.172102] drm_ioctl+0x320/0x370
[ 24.176135] drm_compat_ioctl+0x40/0xdc
[ 24.180621] __arm64_compat_sys_ioctl+0xe0/0x150
[ 24.185904] invoke_syscall+0x80/0x114
[ 24.190302] el0_svc_common.constprop.3+0xc4/0xf8
[ 24.195673] do_el0_svc_compat+0x2c/0x54
[ 24.200241] el0_svc_compat+0x4c/0xe4
[ 24.204544] el0t_32_sync_handler+0xc4/0xf4
[ 24.209378] el0t_32_sync+0x174/0x178
[ 24.213680] -> #3 (crtc_ww_class_mutex){+.+.}-{3:3}:
[ 24.220308] __ww_mutex_lock.constprop.20+0xe8/0x878
[ 24.225951] ww_mutex_lock+0x60/0xd0
[ 24.230166] modeset_lock+0x190/0x19c
[ 24.234467] drm_modeset_lock+0x34/0x54
[ 24.238953] drmm_mode_config_init+0x550/0x764
[ 24.244065] msm_drm_bind+0x170/0x59c
[ 24.248374] try_to_bring_up_master+0x244/0x294
[ 24.253572] __component_add+0xf4/0x14c
[ 24.258057] component_add+0x2c/0x38
[ 24.262273] dsi_dev_attach+0x2c/0x38
[ 24.266575] dsi_host_attach+0xc4/0x120
[ 24.271060] mipi_dsi_attach+0x34/0x48
[ 24.275456] devm_mipi_dsi_attach+0x28/0x68
[ 24.280298] ti_sn_bridge_probe+0x2b4/0x2dc
[ 24.285137] auxiliary_bus_probe+0x78/0x90
[ 24.289893] really_probe+0x1e4/0x3d8
[ 24.294194] __driver_probe_device+0x14c/0x164
[ 24.299298] driver_probe_device+0x54/0xf8
[ 24.304043] __device_attach_driver+0xb4/0x118
[ 24.309145] bus_for_each_drv+0xb0/0xd4
[ 24.313628] __device_attach+0xcc/0x158
[ 24.318112] device_initial_probe+0x24/0x30
[ 24.322954] bus_probe_device+0x38/0x9c
[ 24.327439] deferred_probe_work_func+0xd4/0xf0
[ 24.332628] process_one_work+0x2f0/0x498
[ 24.337289] process_scheduled_works+0x44/0x48
[ 24.342391] worker_thread+0x1e4/0x26c
[ 24.346788] kthread+0xe4/0xf4
[ 24.350470] ret_from_fork+0x10/0x20
[ 24.354683]
[ 24.354683]
[ 24.354683] -> #2 (crtc_ww_class_acquire){+.+.}-{0:0}:
[ 24.361489] drm_modeset_acquire_init+0xe4/0x138
[ 24.366777] drm_helper_probe_detect_ctx+0x44/0x114
[ 24.372327] check_connector_changed+0xbc/0x198
[ 24.377517] drm_helper_hpd_irq_event+0xcc/0x11c
[ 24.382804] dsi_hpd_worker+0x24/0x30
[ 24.387104] process_one_work+0x2f0/0x498
[ 24.391762] worker_thread+0x1d0/0x26c
[ 24.396158] kthread+0xe4/0xf4
[ 24.399840] ret_from_fork+0x10/0x20
[ 24.404053]
[ 24.404053] -> #1 (&dev->mode_config.mutex){+.+.}-{3:3}:
[ 24.411032] __mutex_lock+0xc8/0x384
[ 24.415247] mutex_lock_nested+0x54/0x74
[ 24.419819] dp_panel_read_sink_caps+0x23c/0x26c
[ 24.425108] dp_display_process_hpd_high+0x34/0xd4
[ 24.430570] dp_display_usbpd_configure_cb+0x30/0x3c
[ 24.436205] hpd_event_thread+0x2ac/0x550
[ 24.440864] kthread+0xe4/0xf4
[ 24.444544] ret_from_fork+0x10/0x20
[ 24.448757]
[ 24.448757] -> #0 (&dp->event_mutex){+.+.}-{3:3}:
[ 24.455116] __lock_acquire+0xe2c/0x10d8
[ 24.459690] lock_acquire+0x1ac/0x2d0
[ 24.463988] __mutex_lock+0xc8/0x384
[ 24.468201] mutex_lock_nested+0x54/0x74
[ 24.472773] msm_dp_display_enable+0x58/0x164
[ 24.477789] dp_bridge_enable+0x24/0x30
[ 24.482273] drm_atomic_bridge_chain_enable+0x78/0x9c
[ 24.488006] drm_atomic_helper_commit_modeset_enables+0x1bc/0x244
[ 24.494801] msm_atomic_commit_tail+0x248/0x3d0
[ 24.499992] commit_tail+0x7c/0xfc
[ 24.504031] drm_atomic_helper_commit+0x158/0x15c
[ 24.509404] drm_atomic_commit+0x60/0x74
[ 24.513976] drm_mode_atomic_ioctl+0x6b0/0x908
[ 24.519079] drm_ioctl_kernel+0xe8/0x168
[ 24.523650] drm_ioctl+0x320/0x370
[ 24.527689] drm_compat_ioctl+0x40/0xdc
[ 24.532175] __arm64_compat_sys_ioctl+0xe0/0x150
[ 24.537463] invoke_syscall+0x80/0x114
[ 24.541861] el0_svc_common.constprop.3+0xc4/0xf8
[ 24.547235] do_el0_svc_compat+0x2c/0x54
[ 24.551806] el0_svc_compat+0x4c/0xe4
[ 24.556106] el0t_32_sync_handler+0xc4/0xf4
[ 24.560948] el0t_32_sync+0x174/0x178
Changes in v2:
-- add circular lockiing trace
Fixes: d4aca422539c ("drm/msm/dp: always add fail-safe mode into connector mode list")
I'll carry over this from Stephen's reply to the previous iteration:
Reported-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
Signed-off-by: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx>
---
drivers/gpu/drm/msm/dp/dp_display.c | 6 ++++++
drivers/gpu/drm/msm/dp/dp_panel.c | 20 ++++++++++----------
drivers/gpu/drm/msm/dp/dp_panel.h | 1 +
3 files changed, 17 insertions(+), 10 deletions(-)
diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index 178b774..a42732b 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -580,6 +580,12 @@ static int dp_hpd_plug_handle(struct dp_display_private *dp, u32 data)
dp->dp_display.connector_type, state);
mutex_unlock(&dp->event_mutex);
+ /*
+ * add fail safe mode outside event_mutex scope
+ * to avoid potiential circular lock with drm thread
+ */
+ dp_panel_add_fail_safe_mode(dp->dp_display.connector);
+
/* uevent will complete connection part */
return 0;
};
diff --git a/drivers/gpu/drm/msm/dp/dp_panel.c b/drivers/gpu/drm/msm/dp/dp_panel.c
index f141872..26c3653 100644
--- a/drivers/gpu/drm/msm/dp/dp_panel.c
+++ b/drivers/gpu/drm/msm/dp/dp_panel.c
@@ -151,6 +151,15 @@ static int dp_panel_update_modes(struct drm_connector *connector,
return rc;
}
+void dp_panel_add_fail_safe_mode(struct drm_connector *connector)
+{
+ /* fail safe edid */
+ mutex_lock(&connector->dev->mode_config.mutex);
+ if (drm_add_modes_noedid(connector, 640, 480))
+ drm_set_preferred_mode(connector, 640, 480);
+ mutex_unlock(&connector->dev->mode_config.mutex);
+}
+
int dp_panel_read_sink_caps(struct dp_panel *dp_panel,
struct drm_connector *connector)
{
@@ -207,16 +216,7 @@ int dp_panel_read_sink_caps(struct dp_panel *dp_panel,
goto end;
}
- /* fail safe edid */
- mutex_lock(&connector->dev->mode_config.mutex);
- if (drm_add_modes_noedid(connector, 640, 480))
- drm_set_preferred_mode(connector, 640, 480);
- mutex_unlock(&connector->dev->mode_config.mutex);
- } else {
- /* always add fail-safe mode as backup mode */
- mutex_lock(&connector->dev->mode_config.mutex);
- drm_add_modes_noedid(connector, 640, 480);
- mutex_unlock(&connector->dev->mode_config.mutex);
+ dp_panel_add_fail_safe_mode(connector);
}
if (panel->aux_cfg_update_done) {
diff --git a/drivers/gpu/drm/msm/dp/dp_panel.h b/drivers/gpu/drm/msm/dp/dp_panel.h
index 9023e5b..99739ea 100644
--- a/drivers/gpu/drm/msm/dp/dp_panel.h
+++ b/drivers/gpu/drm/msm/dp/dp_panel.h
@@ -59,6 +59,7 @@ int dp_panel_init_panel_info(struct dp_panel *dp_panel);
int dp_panel_deinit(struct dp_panel *dp_panel);
int dp_panel_timing_cfg(struct dp_panel *dp_panel);
void dp_panel_dump_regs(struct dp_panel *dp_panel);
+void dp_panel_add_fail_safe_mode(struct drm_connector *connector);
int dp_panel_read_sink_caps(struct dp_panel *dp_panel,
struct drm_connector *connector);
u32 dp_panel_get_mode_bpp(struct dp_panel *dp_panel, u32 mode_max_bpp,
--
With best wishes
Dmitry
