drm/i915/selftests: Reorder tasklet_disable vs local_bh_disable

Due to a change in requirements that disallows tasklet_disable() being
called from atomic context, rearrange the selftest to avoid doing so.

<3> [324.942939] BUG: sleeping function called from invalid context at kernel/softirq.c:888
<3> [324.942952] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 5601, name: i915_selftest
<4> [324.942960] 1 lock held by i915_selftest/5601:
<4> [324.942963]  #0: ffff888101d19240 (&dev->mutex){....}-{3:3}, at: device_driver_attach+0x18/0x50
<3> [324.942987] Preemption disabled at:
<3> [324.942990] [<ffffffffa026fbd2>] live_hold_reset.part.65+0xc2/0x2f0 [i915]
<4> [324.943255] CPU: 0 PID: 5601 Comm: i915_selftest Tainted: G     U            5.13.0-rc5-CI-CI_DRM_10197+ #1
<4> [324.943259] Hardware name: Intel Corp. Geminilake/GLK RVP2 LP4SD (07), BIOS GELKRVPA.X64.0062.B30.1708222146 08/22/2017
<4> [324.943263] Call Trace:
<4> [324.943267]  dump_stack+0x7f/0xad
<4> [324.943276]  ___might_sleep.cold.123+0xf2/0x106
<4> [324.943286]  tasklet_unlock_wait+0x2e/0xb0
<4> [324.943291]  ? ktime_get_raw+0x81/0x120
<4> [324.943305]  live_hold_reset.part.65+0x1ab/0x2f0 [i915]
<4> [324.943500]  __i915_subtests.cold.7+0x42/0x92 [i915]
<4> [324.943723]  ? __i915_live_teardown+0x50/0x50 [i915]
<4> [324.943922]  ? __intel_gt_live_setup+0x30/0x30 [i915]

Fixes: da044747 ("tasklets: Replace spin wait in tasklet_unlock_wait()")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210611060838.647973-1-thomas.hellstrom@linux.intel.com

drivers/gpu/drm/i915/gt/selftest_execlists.c

@@ -551,6 +551,32 @@ static int live_pin_rewind(void *arg)
 	return err;
 }
 
+static int engine_lock_reset_tasklet(struct intel_engine_cs *engine)
+{
+	tasklet_disable(&engine->execlists.tasklet);
+	local_bh_disable();
+
+	if (test_and_set_bit(I915_RESET_ENGINE + engine->id,
+			     &engine->gt->reset.flags)) {
+		local_bh_enable();
+		tasklet_enable(&engine->execlists.tasklet);
+
+		intel_gt_set_wedged(engine->gt);
+		return -EBUSY;
+	}
+
+	return 0;
+}
+
+static void engine_unlock_reset_tasklet(struct intel_engine_cs *engine)
+{
+	clear_and_wake_up_bit(I915_RESET_ENGINE + engine->id,
+			      &engine->gt->reset.flags);
+
+	local_bh_enable();
+	tasklet_enable(&engine->execlists.tasklet);
+}
+
 static int live_hold_reset(void *arg)
 {
 	struct intel_gt *gt = arg;
@@ -598,15 +624,9 @@ static int live_hold_reset(void *arg)
 
 		/* We have our request executing, now remove it and reset */
 
-		local_bh_disable();
-		if (test_and_set_bit(I915_RESET_ENGINE + id,
-				     &gt->reset.flags)) {
-			local_bh_enable();
-			intel_gt_set_wedged(gt);
-			err = -EBUSY;
+		err = engine_lock_reset_tasklet(engine);
+		if (err)
 			goto out;
-		}
-		tasklet_disable(&engine->execlists.tasklet);
 
 		engine->execlists.tasklet.callback(&engine->execlists.tasklet);
 		GEM_BUG_ON(execlists_active(&engine->execlists) != rq);
@@ -618,10 +638,7 @@ static int live_hold_reset(void *arg)
 		__intel_engine_reset_bh(engine, NULL);
 		GEM_BUG_ON(rq->fence.error != -EIO);
 
-		tasklet_enable(&engine->execlists.tasklet);
-		clear_and_wake_up_bit(I915_RESET_ENGINE + id,
-				      &gt->reset.flags);
-		local_bh_enable();
+		engine_unlock_reset_tasklet(engine);
 
 		/* Check that we do not resubmit the held request */
 		if (!i915_request_wait(rq, 0, HZ / 5)) {
@@ -4585,15 +4602,9 @@ static int reset_virtual_engine(struct intel_gt *gt,
 	GEM_BUG_ON(engine == ve->engine);
 
 	/* Take ownership of the reset and tasklet */
-	local_bh_disable();
-	if (test_and_set_bit(I915_RESET_ENGINE + engine->id,
-			     &gt->reset.flags)) {
-		local_bh_enable();
-		intel_gt_set_wedged(gt);
-		err = -EBUSY;
+	err = engine_lock_reset_tasklet(engine);
+	if (err)
 		goto out_heartbeat;
-	}
-	tasklet_disable(&engine->execlists.tasklet);
 
 	engine->execlists.tasklet.callback(&engine->execlists.tasklet);
 	GEM_BUG_ON(execlists_active(&engine->execlists) != rq);
@@ -4612,9 +4623,7 @@ static int reset_virtual_engine(struct intel_gt *gt,
 	GEM_BUG_ON(rq->fence.error != -EIO);
 
 	/* Release our grasp on the engine, letting CS flow again */
-	tasklet_enable(&engine->execlists.tasklet);
-	clear_and_wake_up_bit(I915_RESET_ENGINE + engine->id, &gt->reset.flags);
-	local_bh_enable();
+	engine_unlock_reset_tasklet(engine);
 
 	/* Check that we do not resubmit the held request */
 	i915_request_get(rq);