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2230387314
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Janusz Krzysztofik 2230387314 drm/i915: Fix harmful driver register/unregister asymmetry 
Starting with commit ec3e00b4ee ("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.  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_wakeref)
<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
...

Moreover, that unexpected PM reference is left untouched (not released)
but overwritten, then that triggers another kernel warning at driver
release phase:

<4> [526.685700] ------------[ cut here ]------------
<4> [526.685706] i915 0000:00:02.0: [drm] i915 raw-wakerefs=1 wakelocks=1 on cleanup
<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 registration failure.  That wakeref is
then left held forever once its handle gets lost overwritten with another
wakeref, hence another WARN() is 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
69d6bf5c37 ("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.

v5: Drop unsigned keyword from ret variable declaration (Krzysztof),
  - keep the "Failed to register driver for userspace access" error
    message (Krzysztof),
  - split PXP cleanup addition to rewind path out to a separate patch.
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/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@intel.com>
Cc: Chris Wilson <chris.p.wilson@linux.intel.com>
Cc: Ashutosh Dixit <ashutosh.dixit@intel.com>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Cc: Krzysztof Niemiec <krzysztof.niemiec@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Reviewed-by: Krzysztof Niemiec <krzysztof.niemiec@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250314205202.809563-8-janusz.krzysztofik@linux.intel.com
2025-03-19 02:44:42 +01:00
arch Linux 6.14-rc4 2025-02-25 17:36:09 +10:00
block block-6.14-20250221 2025-02-21 09:36:28 -08:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
Documentation UAPI Changes: 2025-02-27 10:08:29 +10:00
drivers drm/i915: Fix harmful driver register/unregister asymmetry 2025-03-19 02:44:42 +01:00
fs smb: client: Add check for next_buffer in receive_encrypted_standard() 2025-02-20 12:10:39 -06:00
include drm/fb-helper: Remove struct drm_fb_helper.fb_probe 2025-03-05 21:48:50 +01:00
init Kbuild updates for v6.14 2025-01-31 12:07:07 -08:00
io_uring io_uring-6.14-20250221 2025-02-21 09:17:56 -08:00
ipc treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
kernel Two RSEQ fixes: 2025-02-22 09:30:04 -08:00
lib test_xarray: fix failure in check_pause when CONFIG_XARRAY_MULTI is not defined 2025-02-17 22:40:04 -08:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm kasan: don't call find_vm_area() in a PREEMPT_RT kernel 2025-02-17 22:40:04 -08:00
net BPF fixes: 2025-02-20 15:37:17 -08:00
rust Driver core api addition for 6.14-rc3 2025-02-16 12:54:42 -08:00
samples Driver core api addition for 6.14-rc3 2025-02-16 12:54:42 -08:00
scripts modpost: Fix a few typos in a comment 2025-02-16 03:10:58 +09:00
security Redo of pathname patternization and fix spelling errors. 2025-02-11 10:19:36 -08:00
sound Linux 6.14-rc4 2025-02-25 17:36:09 +10:00
tools tracing fixes for v6.14: 2025-02-22 09:03:54 -08:00
usr kbuild: Drop support for include/asm-<arch> in headers_check.pl 2024-12-21 11:43:17 +09:00
virt KVM: remove kvm_arch_post_init_vm 2025-02-04 11:27:45 -05:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: give Clippy the minimum supported Rust version 2025-01-10 00:17:25 +01:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: use host dylib naming convention to support macOS 2025-01-10 01:01:24 +01:00
.mailmap mailmap: update Nick's entry 2025-02-17 22:40:03 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING
CREDITS drm-misc-next for v6.15: 2025-02-14 10:24:02 +10:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS UAPI Changes: 2025-02-27 10:08:29 +10:00
Makefile Linux 6.14-rc4 2025-02-23 12:32:57 -08:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.