Re: [Intel-gfx] [PATCH] drm/i915/reset: Handle reset timeouts under unrelated kernel hangs

["Dixit, Ashutosh" <ashutosh.dixit@intel.com>]

On Tue, 28 Jun 2022 12:17:41 -0700, Ashutosh Dixit wrote:
>
> From: Chris Wilson <chris@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.
>
> Bug: https://gitlab.freedesktop.org/drm/intel/-/issues/3575
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_reset.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
> index a5338c3fde7a0..e72744f6faedc 100644
> --- a/drivers/gpu/drm/i915/gt/intel_reset.c
> +++ b/drivers/gpu/drm/i915/gt/intel_reset.c
> @@ -1259,12 +1259,9 @@ static void intel_gt_reset_global(struct intel_gt *gt,
>	kobject_uevent_env(kobj, KOBJ_CHANGE, reset_event);
>
>	/* Use a watchdog to ensure that our reset completes */
> -	intel_wedge_on_timeout(&w, gt, 5 * HZ) {
> +	intel_wedge_on_timeout(&w, gt, 60 * HZ) {

How about we take one step at a time so if we are moving
synchronize_srcu_expedited() out of the reset watchdog, we leave the
timeout to the previous 5s? With the original timeout restored this patch
is:

Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>

>		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)) {
> --
> 2.36.1
>