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[109.252.193.47]) by smtp.googlemail.com with ESMTPSA id t10sm1607291lfp.162.2021.03.22.09.01.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 22 Mar 2021 09:01:35 -0700 (PDT) Subject: Re: [PATCH v5 01/21] gpu: host1x: Use different lock classes for each client To: Mikko Perttunen , Thierry Reding Cc: jonathanh@nvidia.com, airlied@linux.ie, daniel@ffwll.ch, linux-tegra@vger.kernel.org, dri-devel@lists.freedesktop.org, talho@nvidia.com, bhuntsman@nvidia.com References: <20210111130019.3515669-1-mperttunen@nvidia.com> <20210111130019.3515669-2-mperttunen@nvidia.com> <6615105f-ccf1-7833-512c-090817c47952@gmail.com> <645366c2-c500-efcc-f44c-b933f6f470c4@nvidia.com> From: Dmitry Osipenko Message-ID: <6dec95ac-bd92-9434-76ba-eb7fcb316f49@gmail.com> Date: Mon, 22 Mar 2021 19:01:34 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <645366c2-c500-efcc-f44c-b933f6f470c4@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-tegra@vger.kernel.org 22.03.2021 18:19, Mikko Perttunen пишет: > On 22.3.2021 16.48, Dmitry Osipenko wrote: >> 22.03.2021 17:46, Thierry Reding пишет: >>> On Mon, Jan 11, 2021 at 02:59:59PM +0200, Mikko Perttunen wrote: >>>> To avoid false lockdep warnings, give each client lock a different >>>> lock class, passed from the initialization site by macro. >>>> >>>> Signed-off-by: Mikko Perttunen >>>> --- >>>>   drivers/gpu/host1x/bus.c | 7 ++++--- >>>>   include/linux/host1x.h   | 9 ++++++++- >>>>   2 files changed, 12 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/drivers/gpu/host1x/bus.c b/drivers/gpu/host1x/bus.c >>>> index 347fb962b6c9..8fc79e9cb652 100644 >>>> --- a/drivers/gpu/host1x/bus.c >>>> +++ b/drivers/gpu/host1x/bus.c >>>> @@ -715,13 +715,14 @@ EXPORT_SYMBOL(host1x_driver_unregister); >>>>    * device and call host1x_device_init(), which will in turn call >>>> each client's >>>>    * &host1x_client_ops.init implementation. >>>>    */ >>>> -int host1x_client_register(struct host1x_client *client) >>>> +int __host1x_client_register(struct host1x_client *client, >>>> +               struct lock_class_key *key) >>> >>> I've seen the kbuild robot warn about this because the kerneldoc is now >>> out of date. >>> >>>>   { >>>>       struct host1x *host1x; >>>>       int err; >>>>         INIT_LIST_HEAD(&client->list); >>>> -    mutex_init(&client->lock); >>>> +    __mutex_init(&client->lock, "host1x client lock", key); >>> >>> Should we maybe attempt to make this unique? Could we use something like >>> dev_name(client->dev) for this? >> >> I'm curious who the lockdep warning could be triggered at all, I don't >> recall ever seeing it. Mikko, could you please clarify how to reproduce >> the warning? >> > > This is pretty difficult to read but I guess it's some interaction > related to the delayed initialization of host1x clients? In any case, I > consistently get it at boot (though it may be triggered by vic probe > instead of nvdec). > > I'll fix the kbuild robot warnings and see if I can add a > client-specific lock name for v6. Thank you for the clarification! We now actually have a similar problem on Tegra20 after fixing the coupling of display controllers using the dc1_client->parent=dc0_client and I see the same warning when DC1 is enabled. [ 3.808338] ============================================ [ 3.808355] WARNING: possible recursive locking detected [ 3.808376] 5.12.0-rc3-next-20210319-00176-g60867e51e180 #7219 Tainted: G W [ 3.808406] -------------------------------------------- [ 3.808421] kworker/1:2/108 is trying to acquire lock: [ 3.808449] c36b70a4 (&client->lock){+.+.}-{3:3}, at: host1x_client_resume+0x17/0x58 [ 3.808586] but task is already holding lock: [ 3.808603] c34df8a4 (&client->lock){+.+.}-{3:3}, at: host1x_client_resume+0x17/0x58 [ 3.808712] other info that might help us debug this: [ 3.808729] Possible unsafe locking scenario: [ 3.808744] CPU0 [ 3.808757] ---- [ 3.808771] lock(&client->lock); [ 3.808810] lock(&client->lock); [ 3.808821] *** DEADLOCK *** [ 3.808825] May be due to missing lock nesting notation [ 3.808829] 15 locks held by kworker/1:2/108: [ 3.808836] #0: c20068a8 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x15a/0x608 [ 3.808878] #1: c2bbbf18 (deferred_probe_work){+.+.}-{0:0}, at: process_one_work+0x15a/0x608 [ 3.808912] #2: c366d4d8 (&dev->mutex){....}-{3:3}, at: __device_attach+0x29/0xdc [ 3.808953] #3: c141a980 (devices_lock){+.+.}-{3:3}, at: host1x_client_register+0x35/0xfc [ 3.808986] #4: c34df64c (&host1x->devices_lock){+.+.}-{3:3}, at: host1x_client_register+0x51/0xfc [ 3.809017] #5: c34ed4d8 (&dev->mutex){....}-{3:3}, at: __device_attach+0x29/0xdc [ 3.809050] #6: c13faf5c (registration_lock){+.+.}-{3:3}, at: register_framebuffer+0x2d/0x274 [ 3.809092] #7: c132566c (console_lock){+.+.}-{0:0}, at: register_framebuffer+0x219/0x274 [ 3.809124] #8: c36e7848 (&fb_info->lock){+.+.}-{3:3}, at: register_framebuffer+0x19f/0x274 [ 3.809157] #9: c36d2d6c (&helper->lock){+.+.}-{3:3}, at: __drm_fb_helper_restore_fbdev_mode_unlocked+0x41/0x8c [ 3.809199] #10: c36f00e8 (&dev->master_mutex){+.+.}-{3:3}, at: drm_master_internal_acquire+0x17/0x28 [ 3.809233] #11: c36d2c50 (&client->modeset_mutex){+.+.}-{3:3}, at: drm_client_modeset_commit_locked+0x1d/0x138 [ 3.809272] #12: c2bbba28 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_client_modeset_commit_atomic+0x2f/0x1c4 [ 3.809306] #13: c36e6448 (crtc_ww_class_mutex){+.+.}-{3:3}, at: drm_modeset_backoff+0x63/0x190 [ 3.809337] #14: c34df8a4 (&client->lock){+.+.}-{3:3}, at: host1x_client_resume+0x17/0x58 [ 3.809369] stack backtrace: [ 3.809375] CPU: 1 PID: 108 Comm: kworker/1:2 Tainted: G W 5.12.0-rc3-next-20210319-00176-g60867e51e180 #7219 [ 3.809387] Hardware name: NVIDIA Tegra SoC (Flattened Device Tree) [ 3.809396] Workqueue: events deferred_probe_work_func [ 3.809417] [] (unwind_backtrace) from [] (show_stack+0x11/0x14) [ 3.809447] [] (show_stack) from [] (dump_stack+0x9f/0xb8) [ 3.809467] [] (dump_stack) from [] (__lock_acquire+0x7fb/0x253c) [ 3.809495] [] (__lock_acquire) from [] (lock_acquire+0xf3/0x420) [ 3.809516] [] (lock_acquire) from [] (__mutex_lock+0x87/0x814) [ 3.809544] [] (__mutex_lock) from [] (mutex_lock_nested+0x19/0x20) [ 3.809565] [] (mutex_lock_nested) from [] (host1x_client_resume+0x17/0x58) [ 3.809587] [] (host1x_client_resume) from [] (host1x_client_resume+0x1f/0x58) [ 3.809604] [] (host1x_client_resume) from [] (tegra_crtc_atomic_enable+0x33/0x21c4) [ 3.809634] [] (tegra_crtc_atomic_enable) from [] (drm_atomic_helper_commit_modeset_enables+0x131/0x16c) [ 3.809667] [] (drm_atomic_helper_commit_modeset_enables) from [] (drm_atomic_helper_commit_tail_rpm+0x1d/0x4c) [ 3.809691] [] (drm_atomic_helper_commit_tail_rpm) from [] (tegra_atomic_commit_tail+0x83/0x84) [ 3.809712] [] (tegra_atomic_commit_tail) from [] (commit_tail+0x71/0x138) [ 3.809732] [] (commit_tail) from [] (drm_atomic_helper_commit+0xf1/0x114) [ 3.809753] [] (drm_atomic_helper_commit) from [] (drm_client_modeset_commit_atomic+0x199/0x1c4) [ 3.809777] [] (drm_client_modeset_commit_atomic) from [] (drm_client_modeset_commit_locked+0x3d/0x138) [ 3.809798] [] (drm_client_modeset_commit_locked) from [] (drm_client_modeset_commit+0x1b/0x2c) [ 3.809818] [] (drm_client_modeset_commit) from [] (__drm_fb_helper_restore_fbdev_mode_unlocked+0x73/0x8c) [ 3.809842] [] (__drm_fb_helper_restore_fbdev_mode_unlocked) from [] (drm_fb_helper_set_par+0x2d/0x4c) [ 3.809862] [] (drm_fb_helper_set_par) from [] (fbcon_init+0x1cb/0x370) [ 3.809883] [] (fbcon_init) from [] (visual_init+0x8b/0xc8) [ 3.809902] [] (visual_init) from [] (do_bind_con_driver+0x13d/0x2b4) [ 3.809919] [] (do_bind_con_driver) from [] (do_take_over_console+0xdf/0x15c) [ 3.809937] [] (do_take_over_console) from [] (do_fbcon_takeover+0x4f/0x90) [ 3.809955] [] (do_fbcon_takeover) from [] (register_framebuffer+0x1a5/0x274) [ 3.809977] [] (register_framebuffer) from [] (__drm_fb_helper_initial_config_and_unlock+0x29f/0x438) [ 3.809999] [] (__drm_fb_helper_initial_config_and_unlock) from [] (tegra_drm_fb_init+0x25/0x5c) [ 3.810022] [] (tegra_drm_fb_init) from [] (host1x_drm_probe+0x247/0x404) [ 3.810041] [] (host1x_drm_probe) from [] (really_probe+0xb1/0x2a4) [ 3.810064] [] (really_probe) from [] (driver_probe_device+0x3f/0x78) [ 3.810086] [] (driver_probe_device) from [] (bus_for_each_drv+0x4f/0x78) [ 3.810107] [] (bus_for_each_drv) from [] (__device_attach+0x95/0xdc) [ 3.810127] [] (__device_attach) from [] (bus_probe_device+0x5d/0x64) [ 3.810147] [] (bus_probe_device) from [] (device_add+0x293/0x5c0) [ 3.810166] [] (device_add) from [] (host1x_subdev_register+0x8d/0xac) [ 3.810186] [] (host1x_subdev_register) from [] (host1x_client_register+0x8f/0xfc) [ 3.810204] [] (host1x_client_register) from [] (tegra_dc_probe+0x1bf/0x2b0) [ 3.810225] [] (tegra_dc_probe) from [] (platform_probe+0x43/0x80) [ 3.810247] [] (platform_probe) from [] (really_probe+0xb1/0x2a4) [ 3.810266] [] (really_probe) from [] (driver_probe_device+0x3f/0x78) [ 3.810286] [] (driver_probe_device) from [] (bus_for_each_drv+0x4f/0x78) [ 3.810307] [] (bus_for_each_drv) from [] (__device_attach+0x95/0xdc) [ 3.810326] [] (__device_attach) from [] (bus_probe_device+0x5d/0x64) [ 3.810346] [] (bus_probe_device) from [] (deferred_probe_work_func+0x4d/0x70) [ 3.810367] [] (deferred_probe_work_func) from [] (process_one_work+0x1eb/0x608) [ 3.810391] [] (process_one_work) from [] (worker_thread+0xf9/0x3bc) [ 3.810411] [] (worker_thread) from [] (kthread+0xff/0x134) [ 3.810432] [] (kthread) from [] (ret_from_fork+0x11/0x38) [ 3.810449] Exception stack(0xc2bbbfb0 to 0xc2bbbff8)