[PATCH] drm/i915/reset: Handle reset timeouts under unrelated kernel hangs

[Ashutosh Dixit]

From: Chris Wilson <chris at chris-wilson.co.uk>

When resuming after hibernate sometimes we see hangs in unrelated kernel
subsystems. These hangs often result in the following i915 trace:

i915 0000:00:02.0: [drm] *ERROR* \
	intel_gt_reset_global timed out, cancelling all in-flight rendering

implying our reset task has been starved by the hanging kernel subsystem,
causing us to inappropiately declare the system as wedged beyond recovery.

The trace would be caused by our synchronize_srcu_expedited() taking more
than the allowed 5s due to the unrelated kernel hang. But we neither need
to perform that synchronisation inside the reset watchdog, nor do we need
such a short timeout before declaring the device as unrecoverable.

v2: Restore watchdog timeout to the previous 5 seconds (Ashutosh)

Bug: https://gitlab.freedesktop.org/drm/intel/-/issues/3575
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit at intel.com>
Reviewed-by: Ashutosh Dixit <ashutosh.dixit at intel.com>
---
 drivers/gpu/drm/i915/gt/intel_reset.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
index a5338c3fde7a..1cbe65a5b0fd 100644
--- a/drivers/gpu/drm/i915/gt/intel_reset.c
+++ b/drivers/gpu/drm/i915/gt/intel_reset.c
@@ -1262,9 +1262,6 @@ static void intel_gt_reset_global(struct intel_gt *gt,
 	intel_wedge_on_timeout(&w, gt, 5 * HZ) {
 		intel_display_prepare_reset(gt->i915);
 
-		/* Flush everyone using a resource about to be clobbered */
-		synchronize_srcu_expedited(&gt->reset.backoff_srcu);
-
 		intel_gt_reset(gt, engine_mask, reason);
 
 		intel_display_finish_reset(gt->i915);
@@ -1373,6 +1370,9 @@ void intel_gt_handle_error(struct intel_gt *gt,
 		}
 	}
 
+	/* Flush everyone using a resource about to be clobbered */
+	synchronize_srcu_expedited(&gt->reset.backoff_srcu);
+
 	intel_gt_reset_global(gt, engine_mask, msg);
 
 	if (!intel_uc_uses_guc_submission(&gt->uc)) {
-- 
2.34.1