drm/xe: wedge from the timeout handler only after releasing the queue

drm/xe: wedge from the timeout handler only after releasing the queue

A kernel job that exhausts its recovery attempts called
xe_device_declare_wedged() directly from guc_exec_queue_timedout_job(),
while the handler still owned the timed-out job and the queue scheduler
(sched = &q->guc->sched, stopped at the top of the handler).

In the default wedged mode (XE_WEDGED_MODE_UPON_CRITICAL_ERROR),
xe_device_declare_wedged() takes the destructive path in
xe_guc_submit_wedge(): guc_submit_reset_prepare(), xe_guc_submit_stop()
- which calls guc_exec_queue_stop() on every queue, including this one -
softreset and pause-abort. That tears submission down, signals the
in-flight fences and restarts the schedulers. This is the correct
behaviour when the wedge originates outside the TDR, but not when the
TDR itself triggers it: every queue should be torn down except the one
the TDR is currently operating on, which it still owns.

Control then returned to the handler, which kept using the now stale job
and scheduler:

  xe_sched_job_set_error(job, err);
  drm_sched_for_each_pending_job(tmp_job, &sched->base, NULL)
          xe_sched_job_set_error(to_xe_sched_job(tmp_job), -ECANCELED);

drm_sched_for_each_pending_job() warns because the scheduler is no
longer stopped (WARN_ON(!drm_sched_is_stopped())) and the iteration then
dereferences a freed job, faulting on the slab poison:

  Oops: general protection fault ... 0x6b6b6b6b6b6b6c3b
  RIP: guc_exec_queue_timedout_job+...

Defer the wedge until the handler has finished operating on the queue,
right before returning DRM_GPU_SCHED_STAT_NO_HANG, so the teardown no
longer races with this handler's use of @q.

Fixes: 770031ec2312 ("drm/xe: fix job timeout recovery for unstarted jobs and kernel queues")
Suggested-by: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Cc: Sanjay Yadav <sanjay.kumar.yadav@intel.com>
Assisted-by: GitHub-Copilot:claude-opus-4.8
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20260612162414.287971-2-rodrigo.vivi@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
(cherry picked from commit a889e9b06bfdb375fc88b3b2a4b143f621f930c6)
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>