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03:07:51 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH] drm/msm/dp: move add fail safe mode to dp_connector_get_mode() Content-Language: en-GB To: Kuogee Hsieh , robdclark@gmail.com, sean@poorly.run, swboyd@chromium.org, vkoul@kernel.org, daniel@ffwll.ch, airlied@linux.ie, agross@kernel.org, bjorn.andersson@linaro.org Cc: quic_abhinavk@quicinc.com, quic_aravindh@quicinc.com, quic_sbillaka@quicinc.com, freedreno@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org References: <1650671124-14030-1-git-send-email-quic_khsieh@quicinc.com> From: Dmitry Baryshkov In-Reply-To: <1650671124-14030-1-git-send-email-quic_khsieh@quicinc.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On 23/04/2022 02:45, Kuogee Hsieh wrote: > Current DP driver implementation has adding safe mode done at > dp_hpd_plug_handle() which is expected to be executed under event > thread context. > > However there is possible circular locking happen (see blow stack trace) > after edp driver call dp_hpd_plug_handle() from dp_bridge_enable() which > is executed under drm_thread context. > > To break this circular locking, this patch have safe mode added at > dp_connector_get_mode() which is executed under drm thread context. > Therefore no lock acquired required for &dev->mode_config.mutex while > adding fail safe mode since it has been hold by drm thread already. > > ====================================================== > WARNING: possible circular locking dependency detected > 5.15.35-lockdep #6 Tainted: G W > ------------------------------------------------------ > frecon/429 is trying to acquire lock: > ffffff808dc3c4e8 (&dev->mode_config.mutex){+.+.}-{3:3}, at: > dp_panel_add_fail_safe_mode+0x4c/0xa0 > > but task is already holding lock: > ffffff808dc441e0 (&kms->commit_lock[i]){+.+.}-{3:3}, at: lock_crtcs+0xb4/0x124 > > which lock already depends on the new lock. > > the existing dependency chain (in reverse order) is: > > -> #3 (&kms->commit_lock[i]){+.+.}-{3:3}: > __mutex_lock_common+0x174/0x1a64 > mutex_lock_nested+0x98/0xac > lock_crtcs+0xb4/0x124 > msm_atomic_commit_tail+0x330/0x748 > commit_tail+0x19c/0x278 > drm_atomic_helper_commit+0x1dc/0x1f0 > drm_atomic_commit+0xc0/0xd8 > drm_atomic_helper_set_config+0xb4/0x134 > drm_mode_setcrtc+0x688/0x1248 > drm_ioctl_kernel+0x1e4/0x338 > drm_ioctl+0x3a4/0x684 > __arm64_sys_ioctl+0x118/0x154 > invoke_syscall+0x78/0x224 > el0_svc_common+0x178/0x200 > do_el0_svc+0x94/0x13c > el0_svc+0x5c/0xec > el0t_64_sync_handler+0x78/0x108 > el0t_64_sync+0x1a4/0x1a8 > > -> #2 (crtc_ww_class_mutex){+.+.}-{3:3}: > __mutex_lock_common+0x174/0x1a64 > ww_mutex_lock+0xb8/0x278 > modeset_lock+0x304/0x4ac > drm_modeset_lock+0x4c/0x7c > drmm_mode_config_init+0x4a8/0xc50 > msm_drm_init+0x274/0xac0 > msm_drm_bind+0x20/0x2c > try_to_bring_up_master+0x3dc/0x470 > __component_add+0x18c/0x3c0 > component_add+0x1c/0x28 > dp_display_probe+0x954/0xa98 > platform_probe+0x124/0x15c > really_probe+0x1b0/0x5f8 > __driver_probe_device+0x174/0x20c > driver_probe_device+0x70/0x134 > __device_attach_driver+0x130/0x1d0 > bus_for_each_drv+0xfc/0x14c > __device_attach+0x1bc/0x2bc > device_initial_probe+0x1c/0x28 > bus_probe_device+0x94/0x178 > deferred_probe_work_func+0x1a4/0x1f0 > process_one_work+0x5d4/0x9dc > worker_thread+0x898/0xccc > kthread+0x2d4/0x3d4 > ret_from_fork+0x10/0x20 > > -> #1 (crtc_ww_class_acquire){+.+.}-{0:0}: > ww_acquire_init+0x1c4/0x2c8 > drm_modeset_acquire_init+0x44/0xc8 > drm_helper_probe_single_connector_modes+0xb0/0x12dc > drm_mode_getconnector+0x5dc/0xfe8 > drm_ioctl_kernel+0x1e4/0x338 > drm_ioctl+0x3a4/0x684 > __arm64_sys_ioctl+0x118/0x154 > invoke_syscall+0x78/0x224 > el0_svc_common+0x178/0x200 > do_el0_svc+0x94/0x13c > el0_svc+0x5c/0xec > el0t_64_sync_handler+0x78/0x108 > el0t_64_sync+0x1a4/0x1a8 > > -> #0 (&dev->mode_config.mutex){+.+.}-{3:3}: > __lock_acquire+0x2650/0x672c > lock_acquire+0x1b4/0x4ac > __mutex_lock_common+0x174/0x1a64 > mutex_lock_nested+0x98/0xac > dp_panel_add_fail_safe_mode+0x4c/0xa0 > dp_hpd_plug_handle+0x1f0/0x280 > dp_bridge_enable+0x94/0x2b8 > drm_atomic_bridge_chain_enable+0x11c/0x168 > drm_atomic_helper_commit_modeset_enables+0x500/0x740 > msm_atomic_commit_tail+0x3e4/0x748 > commit_tail+0x19c/0x278 > drm_atomic_helper_commit+0x1dc/0x1f0 > drm_atomic_commit+0xc0/0xd8 > drm_atomic_helper_set_config+0xb4/0x134 > drm_mode_setcrtc+0x688/0x1248 > drm_ioctl_kernel+0x1e4/0x338 > drm_ioctl+0x3a4/0x684 > __arm64_sys_ioctl+0x118/0x154 > invoke_syscall+0x78/0x224 > el0_svc_common+0x178/0x200 > do_el0_svc+0x94/0x13c > el0_svc+0x5c/0xec > el0t_64_sync_handler+0x78/0x108 > el0t_64_sync+0x1a4/0x1a8 > > Signed-off-by: Kuogee Hsieh > --- > drivers/gpu/drm/msm/dp/dp_display.c | 6 ------ > drivers/gpu/drm/msm/dp/dp_panel.c | 23 +++++++++++++---------- > 2 files changed, 13 insertions(+), 16 deletions(-) > > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c > index 92cd50f..01453db 100644 > --- a/drivers/gpu/drm/msm/dp/dp_display.c > +++ b/drivers/gpu/drm/msm/dp/dp_display.c > @@ -555,12 +555,6 @@ static int dp_hpd_plug_handle(struct dp_display_private *dp, u32 data) > > 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 1aa9aa8c..23fee42 100644 > --- a/drivers/gpu/drm/msm/dp/dp_panel.c > +++ b/drivers/gpu/drm/msm/dp/dp_panel.c > @@ -151,15 +151,6 @@ 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) > { > @@ -216,7 +207,11 @@ int dp_panel_read_sink_caps(struct dp_panel *dp_panel, > goto end; > } > > - dp_panel_add_fail_safe_mode(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); > } > > if (panel->aux_cfg_update_done) { > @@ -266,6 +261,14 @@ int dp_panel_get_modes(struct dp_panel *dp_panel, > return -EINVAL; > } > > + /* > + * add fail safe mode (640x480) here > + * since we are executed in drm_thread context, > + * no mode_config.mutex acquired required > + */ > + if (drm_add_modes_noedid(connector, 640, 480)) > + drm_set_preferred_mode(connector, 640, 480); > + > if (dp_panel->edid) > return dp_panel_update_modes(connector, dp_panel->edid); > Also, wouldn't calling get_modes() several times make cause adding more and more 640x480 modes to the modes list? -- With best wishes Dmitry From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B835FC433FE for ; Sat, 23 Apr 2022 00:07:56 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id B8C3A10E044; Sat, 23 Apr 2022 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([37.153.55.125]) by smtp.gmail.com with ESMTPSA id v5-20020a196105000000b004718f60c025sm396522lfb.105.2022.04.22.17.07.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 22 Apr 2022 17:07:52 -0700 (PDT) Message-ID: <3b9588d2-d9f6-c96f-b316-953b56b59bfe@linaro.org> Date: Sat, 23 Apr 2022 03:07:51 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH] drm/msm/dp: move add fail safe mode to dp_connector_get_mode() Content-Language: en-GB To: Kuogee Hsieh , robdclark@gmail.com, sean@poorly.run, swboyd@chromium.org, vkoul@kernel.org, daniel@ffwll.ch, airlied@linux.ie, agross@kernel.org, bjorn.andersson@linaro.org References: <1650671124-14030-1-git-send-email-quic_khsieh@quicinc.com> From: Dmitry Baryshkov In-Reply-To: <1650671124-14030-1-git-send-email-quic_khsieh@quicinc.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: quic_sbillaka@quicinc.com, linux-arm-msm@vger.kernel.org, quic_abhinavk@quicinc.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, quic_aravindh@quicinc.com, freedreno@lists.freedesktop.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 23/04/2022 02:45, Kuogee Hsieh wrote: > Current DP driver implementation has adding safe mode done at > dp_hpd_plug_handle() which is expected to be executed under event > thread context. > > However there is possible circular locking happen (see blow stack trace) > after edp driver call dp_hpd_plug_handle() from dp_bridge_enable() which > is executed under drm_thread context. > > To break this circular locking, this patch have safe mode added at > dp_connector_get_mode() which is executed under drm thread context. > Therefore no lock acquired required for &dev->mode_config.mutex while > adding fail safe mode since it has been hold by drm thread already. > > ====================================================== > WARNING: possible circular locking dependency detected > 5.15.35-lockdep #6 Tainted: G W > ------------------------------------------------------ > frecon/429 is trying to acquire lock: > ffffff808dc3c4e8 (&dev->mode_config.mutex){+.+.}-{3:3}, at: > dp_panel_add_fail_safe_mode+0x4c/0xa0 > > but task is already holding lock: > ffffff808dc441e0 (&kms->commit_lock[i]){+.+.}-{3:3}, at: lock_crtcs+0xb4/0x124 > > which lock already depends on the new lock. > > the existing dependency chain (in reverse order) is: > > -> #3 (&kms->commit_lock[i]){+.+.}-{3:3}: > __mutex_lock_common+0x174/0x1a64 > mutex_lock_nested+0x98/0xac > lock_crtcs+0xb4/0x124 > msm_atomic_commit_tail+0x330/0x748 > commit_tail+0x19c/0x278 > drm_atomic_helper_commit+0x1dc/0x1f0 > drm_atomic_commit+0xc0/0xd8 > drm_atomic_helper_set_config+0xb4/0x134 > drm_mode_setcrtc+0x688/0x1248 > drm_ioctl_kernel+0x1e4/0x338 > drm_ioctl+0x3a4/0x684 > __arm64_sys_ioctl+0x118/0x154 > invoke_syscall+0x78/0x224 > el0_svc_common+0x178/0x200 > do_el0_svc+0x94/0x13c > el0_svc+0x5c/0xec > el0t_64_sync_handler+0x78/0x108 > el0t_64_sync+0x1a4/0x1a8 > > -> #2 (crtc_ww_class_mutex){+.+.}-{3:3}: > __mutex_lock_common+0x174/0x1a64 > ww_mutex_lock+0xb8/0x278 > modeset_lock+0x304/0x4ac > drm_modeset_lock+0x4c/0x7c > drmm_mode_config_init+0x4a8/0xc50 > msm_drm_init+0x274/0xac0 > msm_drm_bind+0x20/0x2c > try_to_bring_up_master+0x3dc/0x470 > __component_add+0x18c/0x3c0 > component_add+0x1c/0x28 > dp_display_probe+0x954/0xa98 > platform_probe+0x124/0x15c > really_probe+0x1b0/0x5f8 > __driver_probe_device+0x174/0x20c > driver_probe_device+0x70/0x134 > __device_attach_driver+0x130/0x1d0 > bus_for_each_drv+0xfc/0x14c > __device_attach+0x1bc/0x2bc > device_initial_probe+0x1c/0x28 > bus_probe_device+0x94/0x178 > deferred_probe_work_func+0x1a4/0x1f0 > process_one_work+0x5d4/0x9dc > worker_thread+0x898/0xccc > kthread+0x2d4/0x3d4 > ret_from_fork+0x10/0x20 > > -> #1 (crtc_ww_class_acquire){+.+.}-{0:0}: > ww_acquire_init+0x1c4/0x2c8 > drm_modeset_acquire_init+0x44/0xc8 > drm_helper_probe_single_connector_modes+0xb0/0x12dc > drm_mode_getconnector+0x5dc/0xfe8 > drm_ioctl_kernel+0x1e4/0x338 > drm_ioctl+0x3a4/0x684 > __arm64_sys_ioctl+0x118/0x154 > invoke_syscall+0x78/0x224 > el0_svc_common+0x178/0x200 > do_el0_svc+0x94/0x13c > el0_svc+0x5c/0xec > el0t_64_sync_handler+0x78/0x108 > el0t_64_sync+0x1a4/0x1a8 > > -> #0 (&dev->mode_config.mutex){+.+.}-{3:3}: > __lock_acquire+0x2650/0x672c > lock_acquire+0x1b4/0x4ac > __mutex_lock_common+0x174/0x1a64 > mutex_lock_nested+0x98/0xac > dp_panel_add_fail_safe_mode+0x4c/0xa0 > dp_hpd_plug_handle+0x1f0/0x280 > dp_bridge_enable+0x94/0x2b8 > drm_atomic_bridge_chain_enable+0x11c/0x168 > drm_atomic_helper_commit_modeset_enables+0x500/0x740 > msm_atomic_commit_tail+0x3e4/0x748 > commit_tail+0x19c/0x278 > drm_atomic_helper_commit+0x1dc/0x1f0 > drm_atomic_commit+0xc0/0xd8 > drm_atomic_helper_set_config+0xb4/0x134 > drm_mode_setcrtc+0x688/0x1248 > drm_ioctl_kernel+0x1e4/0x338 > drm_ioctl+0x3a4/0x684 > __arm64_sys_ioctl+0x118/0x154 > invoke_syscall+0x78/0x224 > el0_svc_common+0x178/0x200 > do_el0_svc+0x94/0x13c > el0_svc+0x5c/0xec > el0t_64_sync_handler+0x78/0x108 > el0t_64_sync+0x1a4/0x1a8 > > Signed-off-by: Kuogee Hsieh > --- > drivers/gpu/drm/msm/dp/dp_display.c | 6 ------ > drivers/gpu/drm/msm/dp/dp_panel.c | 23 +++++++++++++---------- > 2 files changed, 13 insertions(+), 16 deletions(-) > > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c > index 92cd50f..01453db 100644 > --- a/drivers/gpu/drm/msm/dp/dp_display.c > +++ b/drivers/gpu/drm/msm/dp/dp_display.c > @@ -555,12 +555,6 @@ static int dp_hpd_plug_handle(struct dp_display_private *dp, u32 data) > > 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 1aa9aa8c..23fee42 100644 > --- a/drivers/gpu/drm/msm/dp/dp_panel.c > +++ b/drivers/gpu/drm/msm/dp/dp_panel.c > @@ -151,15 +151,6 @@ 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) > { > @@ -216,7 +207,11 @@ int dp_panel_read_sink_caps(struct dp_panel *dp_panel, > goto end; > } > > - dp_panel_add_fail_safe_mode(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); > } > > if (panel->aux_cfg_update_done) { > @@ -266,6 +261,14 @@ int dp_panel_get_modes(struct dp_panel *dp_panel, > return -EINVAL; > } > > + /* > + * add fail safe mode (640x480) here > + * since we are executed in drm_thread context, > + * no mode_config.mutex acquired required > + */ > + if (drm_add_modes_noedid(connector, 640, 480)) > + drm_set_preferred_mode(connector, 640, 480); > + > if (dp_panel->edid) > return dp_panel_update_modes(connector, dp_panel->edid); > Also, wouldn't calling get_modes() several times make cause adding more and more 640x480 modes to the modes list? -- With best wishes Dmitry