On 2025-03-11 at 21:04:56 GMT, Janusz Krzysztofik 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, and continue only with remaining probe steps. However, the
> _unregister() counterpart called at driver remove knows nothing about that
> skip and executes reverts of all those steps, with 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() was already there. It triggers
> the drm_WARN_ON() when it finds a reference to a wakeref taken on device
> probe and not released after device register failure. That wakeref is
> then left held forever once its handle gets lost overwritten with another
> wakeref, hence the WARN() called from intel_runtime_pm_driver_release().
>
> 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 when the return was added.
>
> 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").
>
> Fix the asymmetry by failing the driver probe on device registration
> failure and going through rewind paths.
>
> For that to work as expected, we apparently need to start the rewind path
> of i915_driver_register() with drm_dev_unregister(), even if
> drm_dev_register() returned an error.
>
> Also, in rewind path of the i915_driver_probe() we need to clean up PXP
> initialization before it's safe to call other hardware cleanup routines.
> The intel_pxp_init() without a corresponding cleanup was added to
> i915_driver_probe() with commit f67986b0119c04 ("drm/i915/pxp: Promote pxp
> subsystem to top-level of i915").
>
> v4: Switch to taking an error rewind path on device registration failure
> (Krzysztof, Lucas).
> 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: Alan Previn <alan.previn.teres.alexis@xxxxxxxxx>
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx>
> Cc: Krzysztof Niemiec <krzysztof.niemiec@xxxxxxxxx>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_driver.c | 22 +++++++++++++++-------
> 1 file changed, 15 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_driver.c b/drivers/gpu/drm/i915/i915_driver.c
> index ce3cc93ea211b..dcf723da8d409 100644
> --- a/drivers/gpu/drm/i915/i915_driver.c
> +++ b/drivers/gpu/drm/i915/i915_driver.c
> @@ -622,11 +622,11 @@ static void i915_driver_hw_remove(struct drm_i915_private *dev_priv)
> * Perform any steps necessary to make the driver available via kernel
> * internal or userspace interfaces.
> */
> -static void i915_driver_register(struct drm_i915_private *dev_priv)
> +static int i915_driver_register(struct drm_i915_private *dev_priv)
> {
> struct intel_display *display = &dev_priv->display;
> struct intel_gt *gt;
> - unsigned int i;
> + unsigned int i, ret;
drm_dev_register() returns int, i915_driver_probe() expects int from
from the functions it calls (including this one), and this one is
defined as static int, so dropping the unsigned keyword for ret feels
more appropriate.
>
> i915_gem_driver_register(dev_priv);
> i915_pmu_register(dev_priv);
> @@ -634,10 +634,12 @@ static void i915_driver_register(struct drm_i915_private *dev_priv)
> intel_vgpu_register(dev_priv);
>
> /* Reveal our presence to userspace */
> - if (drm_dev_register(&dev_priv->drm, 0)) {
> - drm_err(&dev_priv->drm,
> - "Failed to register driver for userspace access!\n");
> - return;
> + ret = drm_dev_register(&dev_priv->drm, 0);
> + if (ret) {
> + drm_dev_unregister(&dev_priv->drm);
> + i915_pmu_unregister(dev_priv);
> + i915_gem_driver_unregister(dev_priv);
> + return ret;
> }
>
I'd keep the "Failed to register driver for userspace access" error
message.
Thanks
Krzysztof
> i915_debugfs_register(dev_priv);
> @@ -660,6 +662,8 @@ static void i915_driver_register(struct drm_i915_private *dev_priv)
>
> if (i915_switcheroo_register(dev_priv))
> drm_err(&dev_priv->drm, "Failed to register vga switcheroo!\n");
> +
> + return 0;
> }
>
> /**
> @@ -834,7 +838,9 @@ int i915_driver_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
> if (ret)
> goto out_cleanup_gem;
>
> - i915_driver_register(i915);
> + ret = i915_driver_register(i915);
> + if (ret)
> + goto out_cleanup_pxp;
>
> enable_rpm_wakeref_asserts(&i915->runtime_pm);
>
> @@ -844,6 +850,8 @@ int i915_driver_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>
> return 0;
>
> +out_cleanup_pxp:
> + intel_pxp_fini(i915);
> out_cleanup_gem:
> i915_gem_suspend(i915);
> i915_gem_driver_remove(i915);
> --
> 2.48.1
>
