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Message-ID: <b6e417b4-f4c5-30fc-ce0e-d5887220bae9@linaro.org>
Date: Tue, 26 Apr 2022 02:17:29 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Kuogee Hsieh <quic_khsieh@...cinc.com>, robdclark@...il.com,
sean@...rly.run, swboyd@...omium.org, vkoul@...nel.org,
daniel@...ll.ch, airlied@...ux.ie, agross@...nel.org,
bjorn.andersson@...aro.org
Cc: quic_abhinavk@...cinc.com, quic_aravindh@...cinc.com,
quic_sbillaka@...cinc.com, freedreno@...ts.freedesktop.org,
dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/msm/dp: add fail safe mode outside of event_mutex
context
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@...omium.org>
> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
> ---
> 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
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