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Jesus Narvaez 0323a5127e drm/i915/guc: Handle race condition where wakeref count drops below 0
There is a rare race condition when preparing for a reset where
guc_lrc_desc_unpin() could be in the process of deregistering a context
while a different thread is scrubbing outstanding contexts and it alters
the context state and does a wakeref put. Then, if there is a failure
with deregister_context(), a second wakeref put could occur. As a result
the wakeref count could drop below 0 and fail an INTEL_WAKEREF_BUG_ON()
check.

Therefore if there is a failure with deregister_context(), undo the
context state changes and do a wakeref put only if the context was set
to be destroyed earlier.

v2: Expand comment to better explain change. (Daniele)
v3: Removed addition to the original comment. (Daniele)

Fixes: 2f2cc53b5f ("drm/i915/guc: Close deregister-context race against CT-loss")
Signed-off-by: Jesus Narvaez <jesus.narvaez@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Cc: Anshuman Gupta <anshuman.gupta@intel.com>
Cc: Mousumi Jana <mousumi.jana@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://lore.kernel.org/r/20250528230551.1855177-1-jesus.narvaez@intel.com
(cherry picked from commit f36a75aba1)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
2025-06-02 12:19:14 +03:00
arch Merge tag 'drm-msm-next-2025-05-16' of https://gitlab.freedesktop.org/drm/msm into drm-next 2025-05-19 11:05:58 +10:00
block block-6.15-20250424 2025-04-25 11:34:39 -07:00
certs
crypto crypto: scompress - increment scomp_scratch_users when already allocated 2025-04-25 10:33:30 +08:00
Documentation Nova changes for v6.16 2025-05-21 05:49:31 +10:00
drivers drm/i915/guc: Handle race condition where wakeref count drops below 0 2025-06-02 12:19:14 +03:00
fs cifs and smb3 client fixes 2025-05-02 14:37:16 -07:00
include Nova changes for v6.16 2025-05-21 05:49:31 +10:00
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kernel tracing updates for v6.15 2025-05-04 10:15:42 -07:00
lib Merge drm/drm-next into drm-misc-next 2025-05-06 09:09:49 +02:00
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Makefile Linux 6.15-rc5 2025-05-04 13:55:04 -07:00
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.