drm/i915: Request watchdog infrastructure

Prepares the plumbing for setting request/fence expiration time. All code
is put in place but is never activated due yet missing ability to actually
configure the timer.

Outline of the basic operation:

A timer is started when request is ready for execution. If the request
completes (retires) before the timer fires, timer is cancelled and nothing
further happens.

If the timer fires request is added to a lockless list and worker queued.
Purpose of this is twofold: a) It allows request cancellation from a more
friendly context and b) coalesces multiple expirations into a single event
of consuming the list.

Worker locklessly consumes the list of expired requests and cancels them
all using previous added i915_request_cancel().

Associated timeout value is stored in rq->context.watchdog.timeout_us.

v2:
 * Log expiration.

v3:
 * Include more information about user timeline in the log message.

v4:
 * Remove obsolete comment and fix formatting. (Matt)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210324121335.2307063-6-tvrtko.ursulin@linux.intel.com

1 files changed, 28 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/gt/intel_gt_requests.c b/drivers/gpu/drm/i915/gt/intel_gt_requests.c
index dc06c78c9eeb..f7e5ce2e2291 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_requests.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt_requests.c
@@ -9,6 +9,7 @@
 #include "i915_drv.h" /* for_each_engine() */
 #include "i915_request.h"
 #include "intel_engine_heartbeat.h"
+#include "intel_execlists_submission.h"
 #include "intel_gt.h"
 #include "intel_gt_pm.h"
 #include "intel_gt_requests.h"
@@ -243,4 +244,31 @@ void intel_gt_fini_requests(struct intel_gt *gt)
 {
 	/* Wait until the work is marked as finished before unloading! */
 	cancel_delayed_work_sync(&gt->requests.retire_work);
+
+	flush_work(&gt->watchdog.work);
+}
+
+void intel_gt_watchdog_work(struct work_struct *work)
+{
+	struct intel_gt *gt =
+		container_of(work, typeof(*gt), watchdog.work);
+	struct i915_request *rq, *rn;
+	struct llist_node *first;
+
+	first = llist_del_all(&gt->watchdog.list);
+	if (!first)
+		return;
+
+	llist_for_each_entry_safe(rq, rn, first, watchdog.link) {
+		if (!i915_request_completed(rq)) {
+			struct dma_fence *f = &rq->fence;
+
+			pr_notice("Fence expiration time out i915-%s:%s:%llx!\n",
+				  f->ops->get_driver_name(f),
+				  f->ops->get_timeline_name(f),
+				  f->seqno);
+			i915_request_cancel(rq, -EINTR);
+		}
+		i915_request_put(rq);
+	}
 }