2f2cc53b5f
If we are at the end of suspend or very early in resume its possible an async fence signal (via rcu_call) is triggered to free_engines which could lead us to the execution of the context destruction worker (after a prior worker flush). Thus, when suspending, insert rcu_barriers at the start of i915_gem_suspend (part of driver's suspend prepare) and again in i915_gem_suspend_late so that all such cases have completed and context destruction list isn't missing anything. In destroyed_worker_func, close the race against CT-loss by checking that CT is enabled before calling into deregister_destroyed_contexts. Based on testing, guc_lrc_desc_unpin may still race and fail as we traverse the GuC's context-destroy list because the CT could be disabled right before calling GuC's CT send function. We've witnessed this race condition once every ~6000-8000 suspend-resume cycles while ensuring workloads that render something onscreen is continuously started just before we suspend (and the workload is small enough to complete and trigger the queued engine/context free-up either very late in suspend or very early in resume). In such a case, we need to unroll the entire process because guc-lrc-unpin takes a gt wakeref which only gets released in the G2H IRQ reply that never comes through in this corner case. Without the unroll, the taken wakeref is leaked and will cascade into a kernel hang later at the tail end of suspend in this function: intel_wakeref_wait_for_idle(>->wakeref) (called by) - intel_gt_pm_wait_for_idle (called by) - wait_for_suspend Thus, do an unroll in guc_lrc_desc_unpin and deregister_destroyed_- contexts if guc_lrc_desc_unpin fails due to CT send falure. When unrolling, keep the context in the GuC's destroy-list so it can get picked up on the next destroy worker invocation (if suspend aborted) or get fully purged as part of a GuC sanitization (end of suspend) or a reset flow. Signed-off-by: Alan Previn <alan.previn.teres.alexis@intel.com> Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com> Tested-by: Mousumi Jana <mousumi.jana@intel.com> Acked-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com> Signed-off-by: Matt Roper <matthew.d.roper@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20231229215143.581619-1-alan.previn.teres.alexis@intel.com
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 Restructured Text 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.