On Wed, 05 Mar 2025, Janusz Krzysztofik <janusz.krzysztofik@xxxxxxxxxxxxxxx> wrote:
> Starting with commit ec3e00b4ee27 ("drm/i915: stop registering if
> drm_dev_register() fails"), we return from i915_driver_register()
> immediately if drm_dev_register() fails, skipping remaining registration
> steps. However, the _unregister() counterpart called at device remove
> knows nothing about that skip and executes reverts of all those steps,
> some of those reverts possibly added or modified later. As a consequence,
> a number of kernel warnings that taint the kernel are triggered:
>
> <3> [525.823143] i915 0000:00:02.0: [drm] *ERROR* Failed to register driver for
> userspace access!
> ...
> <4> [525.831069] ------------[ cut here ]------------
> <4> [525.831071] i915 0000:00:02.0: [drm] drm_WARN_ON(power_domains->init_wakere
> f)
> <4> [525.831095] WARNING: CPU: 6 PID: 3440 at drivers/gpu/drm/i915/display/intel
> _display_power.c:2074 intel_power_domains_disable+0xc2/0xd0 [i915]
> ...
> <4> [525.831328] CPU: 6 UID: 0 PID: 3440 Comm: i915_module_loa Tainted: G U
> 6.14.0-rc1-CI_DRM_16076-g7a632b6798b6+ #1
> ...
> <4> [525.831334] RIP: 0010:intel_power_domains_disable+0xc2/0xd0 [i915]
> ...
> <4> [525.831483] Call Trace:
> <4> [525.831484] <TASK>
> ...
> <4> [525.831943] i915_driver_remove+0x4b/0x140 [i915]
> <4> [525.832028] i915_pci_remove+0x1e/0x40 [i915]
> <4> [525.832099] pci_device_remove+0x3e/0xb0
> <4> [525.832103] device_remove+0x40/0x80
> <4> [525.832107] device_release_driver_internal+0x215/0x280
> ...
> <4> [525.947666] ------------[ cut here ]------------
> <4> [525.947669] kobject: '(null)' (ffff88814f62a218): is not initialized, yet kobject_put() is being called.
> <4> [525.947707] WARNING: CPU: 6 PID: 3440 at lib/kobject.c:734 kobject_put+0xe4/0x200
> ...
> <4> [525.947875] RIP: 0010:kobject_put+0xe4/0x200
> ...
> <4> [525.947909] Call Trace:
> <4> [525.947911] <TASK>
> ...
> <4> [525.947963] intel_gt_sysfs_unregister+0x25/0x40 [i915]
> <4> [525.948133] intel_gt_driver_unregister+0x14/0x80 [i915]
> <4> [525.948291] i915_driver_remove+0x6c/0x140 [i915]
> <4> [525.948411] i915_pci_remove+0x1e/0x40 [i915]
> ...
> <4> [526.441186] ------------[ cut here ]------------
> <4> [526.441191] kernfs: can not remove 'error', no directory
> <4> [526.441211] WARNING: CPU: 1 PID: 3440 at fs/kernfs/dir.c:1684 kernfs_remove_by_name_ns+0xbc/0xc0
> ...
> <4> [526.441536] RIP: 0010:kernfs_remove_by_name_ns+0xbc/0xc0
> ...
> <4> [526.441578] Call Trace:
> <4> [526.441581] <TASK>
> ...
> <4> [526.441686] sysfs_remove_bin_file+0x17/0x30
> <4> [526.441691] i915_gpu_error_sysfs_teardown+0x1d/0x30 [i915]
> <4> [526.442226] i915_teardown_sysfs+0x1c/0x60 [i915]
> <4> [526.442369] i915_driver_remove+0x9d/0x140 [i915]
> <4> [526.442473] i915_pci_remove+0x1e/0x40 [i915]
> ...
> <4> [526.685700] ------------[ cut here ]------------
> <4> [526.685706] i915 0000:00:02.0: [drm] i915 raw-wakerefs=1 wakelocks=1 on cle
> anup
> <4> [526.685734] WARNING: CPU: 1 PID: 3440 at drivers/gpu/drm/i915/intel_runtime
> _pm.c:443 intel_runtime_pm_driver_release+0x75/0x90 [i915]
> ...
> <4> [526.686090] RIP: 0010:intel_runtime_pm_driver_release+0x75/0x90 [i915]
> ...
> <4> [526.686294] Call Trace:
> <4> [526.686296] <TASK>
> ...
> <4> [526.687025] i915_driver_release+0x7e/0xb0 [i915]
> <4> [526.687243] drm_dev_put.part.0+0x47/0x90
> <4> [526.687250] devm_drm_dev_init_release+0x13/0x30
> <4> [526.687255] devm_action_release+0x12/0x30
> <4> [526.687261] release_nodes+0x3a/0x120
> <4> [526.687268] devres_release_all+0x97/0xe0
> <4> [526.687277] device_unbind_cleanup+0x12/0x80
> <4> [526.687282] device_release_driver_internal+0x23a/0x280
> ...
>
> A call to intel_power_domains_disable() that triggeres the drm_WARN_ON()
> and takes another wakeref even if the one taken during driver register was
> not released after device register error, was already there. The WARN()
> triggered by kernfs_remove_by_name_ns() from i915_teardown_sysfs()->
> i915_gpu_error_sysfs_teardown(), formerly i915_teardown_error_capture(),
> was also there. A call to intel_gt_sysfs_unregister() that triggers the
> WARN() from kobject_put() was added to intel_gt_driver_unregister() with
> commit 69d6bf5c3754ff ("drm/i915/gt: Fix memory leaks in per-gt sysfs").
>
> Introduce a flag that indicates device registration status and raise it on
> device registration success. As a minimum (first step), when that flag is
> found not set while unregistering the driver, jump over those reverts of
> registration steps omitted after device registration failure that are not
> ready for being called unconditionally (and trigger kernel warnings).
>
> In case of i915_gt_driver_unregister() called for each GT, omitting it
> proved to introduce new issues. Skip only its problematic
> intel_gt_sysfs_unregister() sub-step.
>
> Other unregister steps seem to be safe but may still occur redundant in
> that scenario -- that will be addressed in follow-up patches.
>
> v3: Based on Andi's commitment on introducing a flag, try to address
> Jani's "must find another way" by finding a better place and name for
> the flag (in hope that's what Jani had on mind),
> - split into a series of patches and limit the scope of the first (this)
> one to a minimum of omitting conditionally only those unregister
> (sub)steps that trigger kernel warnings when not registered.
> v2: Check in _unregister whether the drm_dev_register has succeeded and
> skip some of the _unregister() steps. (Andi)
>
> Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/10047
> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/9820
> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/10131
> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/10887
> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/12817
> Cc: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
> Cc: Chris Wilson <chris.p.wilson@xxxxxxxxxxxxxxx>
> Cc: Ashutosh Dixit <ashutosh.dixit@xxxxxxxxx>
> Cc: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/gt/intel_gt.c | 3 ++-
> drivers/gpu/drm/i915/i915_driver.c | 8 ++++++--
> drivers/gpu/drm/i915/i915_drv.h | 2 ++
> 3 files changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> index 3d3b1ba76e2be..77eb9305a1ff8 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -783,7 +783,8 @@ void intel_gt_driver_unregister(struct intel_gt *gt)
> {
> intel_wakeref_t wakeref;
>
> - intel_gt_sysfs_unregister(gt);
> + if (gt->i915->do_unregister)
> + intel_gt_sysfs_unregister(gt);
> intel_rps_driver_unregister(>->rps);
> intel_gsc_fini(>->gsc);
>
> diff --git a/drivers/gpu/drm/i915/i915_driver.c b/drivers/gpu/drm/i915/i915_driver.c
> index 613084fd00979..2caaeeab1f0f6 100644
> --- a/drivers/gpu/drm/i915/i915_driver.c
> +++ b/drivers/gpu/drm/i915/i915_driver.c
> @@ -638,6 +638,8 @@ static void i915_driver_register(struct drm_i915_private *dev_priv)
> return;
> }
>
> + dev_priv->do_unregister = true;
> +
> i915_debugfs_register(dev_priv);
> i915_setup_sysfs(dev_priv);
>
> @@ -673,7 +675,8 @@ static void i915_driver_unregister(struct drm_i915_private *dev_priv)
> i915_switcheroo_unregister(dev_priv);
>
> intel_runtime_pm_disable(&dev_priv->runtime_pm);
> - intel_power_domains_disable(display);
> + if (dev_priv->do_unregister)
> + intel_power_domains_disable(display);
I still think we must find another way than adding a global
->do_unregister flag.
The i915 core to display interface needs to be unified with xe. This
patch is counter-productive to that goal.
BR,
Jani.
>
> intel_display_driver_unregister(display);
>
> @@ -687,7 +690,8 @@ static void i915_driver_unregister(struct drm_i915_private *dev_priv)
> i915_perf_unregister(dev_priv);
> i915_pmu_unregister(dev_priv);
>
> - i915_teardown_sysfs(dev_priv);
> + if (dev_priv->do_unregister)
> + i915_teardown_sysfs(dev_priv);
> drm_dev_unplug(&dev_priv->drm);
>
> i915_gem_driver_unregister(dev_priv);
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index ffc346379cc2c..0c6cbedaa71fe 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -184,6 +184,8 @@ struct drm_i915_private {
> /* FIXME: Device release actions should all be moved to drmm_ */
> bool do_release;
>
> + bool do_unregister;
> +
> /* i915 device parameters */
> struct i915_params params;
--
Jani Nikula, Intel
