drm/i915: Remove GPU reset dependence on struct_mutex

Now that the submission backends are controlled via their own spinlocks,
with a wave of a magic wand we can lift the struct_mutex requirement
around GPU reset. That is we allow the submission frontend (userspace)
to keep on submitting while we process the GPU reset as we can suspend
the backend independently.

The major change is around the backoff/handoff strategy for performing
the reset. With no mutex deadlock, we no longer have to coordinate with
any waiter, and just perform the reset immediately.

Testcase: igt/gem_mmap_gtt/hang # regresses
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190125132230.22221-3-chris@chris-wilson.co.uk

1 files changed, 18 insertions, 10 deletions

diff --git a/drivers/gpu/drm/i915/intel_hangcheck.c b/drivers/gpu/drm/i915/intel_hangcheck.c
index 741441daae32..5662d6fed523 100644
--- a/drivers/gpu/drm/i915/intel_hangcheck.c
+++ b/drivers/gpu/drm/i915/intel_hangcheck.c
@@ -25,6 +25,17 @@
 #include "i915_drv.h"
 #include "i915_reset.h"
 
+struct hangcheck {
+	u64 acthd;
+	u32 seqno;
+	enum intel_engine_hangcheck_action action;
+	unsigned long action_timestamp;
+	int deadlock;
+	struct intel_instdone instdone;
+	bool wedged:1;
+	bool stalled:1;
+};
+
 static bool instdone_unchanged(u32 current_instdone, u32 *old_instdone)
 {
 	u32 tmp = current_instdone | *old_instdone;
@@ -119,25 +130,22 @@ engine_stuck(struct intel_engine_cs *engine, u64 acthd)
 }
 
 static void hangcheck_load_sample(struct intel_engine_cs *engine,
-				  struct intel_engine_hangcheck *hc)
+				  struct hangcheck *hc)
 {
 	hc->acthd = intel_engine_get_active_head(engine);
 	hc->seqno = intel_engine_get_seqno(engine);
 }
 
 static void hangcheck_store_sample(struct intel_engine_cs *engine,
-				   const struct intel_engine_hangcheck *hc)
+				   const struct hangcheck *hc)
 {
 	engine->hangcheck.acthd = hc->acthd;
 	engine->hangcheck.seqno = hc->seqno;
-	engine->hangcheck.action = hc->action;
-	engine->hangcheck.stalled = hc->stalled;
-	engine->hangcheck.wedged = hc->wedged;
 }
 
 static enum intel_engine_hangcheck_action
 hangcheck_get_action(struct intel_engine_cs *engine,
-		     const struct intel_engine_hangcheck *hc)
+		     const struct hangcheck *hc)
 {
 	if (engine->hangcheck.seqno != hc->seqno)
 		return ENGINE_ACTIVE_SEQNO;
@@ -149,7 +157,7 @@ hangcheck_get_action(struct intel_engine_cs *engine,
 }
 
 static void hangcheck_accumulate_sample(struct intel_engine_cs *engine,
-					struct intel_engine_hangcheck *hc)
+					struct hangcheck *hc)
 {
 	unsigned long timeout = I915_ENGINE_DEAD_TIMEOUT;
 
@@ -265,19 +273,19 @@ static void i915_hangcheck_elapsed(struct work_struct *work)
 	intel_uncore_arm_unclaimed_mmio_detection(dev_priv);
 
 	for_each_engine(engine, dev_priv, id) {
-		struct intel_engine_hangcheck hc;
+		struct hangcheck hc;
 
 		hangcheck_load_sample(engine, &hc);
 		hangcheck_accumulate_sample(engine, &hc);
 		hangcheck_store_sample(engine, &hc);
 
-		if (engine->hangcheck.stalled) {
+		if (hc.stalled) {
 			hung |= intel_engine_flag(engine);
 			if (hc.action != ENGINE_DEAD)
 				stuck |= intel_engine_flag(engine);
 		}
 
-		if (engine->hangcheck.wedged)
+		if (hc.wedged)
 			wedged |= intel_engine_flag(engine);
 	}