tests: add gem_unref_active_buffers

The crucial trick to reproduce the bug is that we need to have
a decent pile of active bos to retire. Because we unref the bo
after having it moved off the active list, our recursion depth
in fdo bug #42180 is limited by the number of active objects that
can retire at the same time.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=42180
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

tests/Makefile.am

@@ -52,6 +52,7 @@ TESTS = getversion \
 	gem_ring_sync_loop \
 	gem_pipe_control_store_loop \
 	gem_hangcheck_forcewake \
+	gem_unref_active_buffers \
 	$(NULL)
 
 HANG = \

tests/gem_unref_active_buffers.c

@@ -0,0 +1,107 @@
+/*
+ * Copyright © 2011 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Authors:
+ *    Daniel Vetter <daniel.vetter@ffwll.ch>
+ *
+ */
+
+/*
+ * Testcase: Unreferencing of active buffers
+ *
+ * Execs buffers and immediately unreferences them, hence the kernel active list
+ * will be the last one to hold a reference on them. Usually libdrm bo caching
+ * prevents that by keeping another reference.
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include "drm.h"
+#include "i915_drm.h"
+#include "drmtest.h"
+#include "intel_bufmgr.h"
+#include "intel_batchbuffer.h"
+#include "intel_gpu_tools.h"
+
+static drm_intel_bufmgr *bufmgr;
+struct intel_batchbuffer *batch;
+static drm_intel_bo *load_bo;
+
+int main(int argc, char **argv)
+{
+	int fd, i;
+
+	fd = drm_open_any();
+
+	bufmgr = drm_intel_bufmgr_gem_init(fd, 4096);
+	if (!bufmgr) {
+		fprintf(stderr, "failed to init libdrm\n");
+		exit(-1);
+	}
+	/* don't enable buffer reuse!! */
+	//drm_intel_bufmgr_gem_enable_reuse(bufmgr);
+
+	batch = intel_batchbuffer_alloc(bufmgr, intel_get_drm_devid(fd));
+	assert(batch);
+
+	/* put some load onto the gpu to keep the light buffers active for long
+	 * enough */
+	for (i = 0; i < 1000; i++) {
+		load_bo = drm_intel_bo_alloc(bufmgr, "target bo", 1024*4096, 4096);
+		if (!load_bo) {
+			fprintf(stderr, "failed to alloc target buffer\n");
+			exit(-1);
+		}
+
+		BEGIN_BATCH(8);
+		OUT_BATCH(XY_SRC_COPY_BLT_CMD |
+			  XY_SRC_COPY_BLT_WRITE_ALPHA |
+			  XY_SRC_COPY_BLT_WRITE_RGB);
+		OUT_BATCH((3 << 24) | /* 32 bits */
+			  (0xcc << 16) | /* copy ROP */
+			  4096);
+		OUT_BATCH(0); /* dst x1,y1 */
+		OUT_BATCH((1024 << 16) | 512);
+		OUT_RELOC(load_bo, I915_GEM_DOMAIN_RENDER, I915_GEM_DOMAIN_RENDER, 0);
+		OUT_BATCH((0 << 16) | 512); /* src x1, y1 */
+		OUT_BATCH(4096);
+		OUT_RELOC(load_bo, I915_GEM_DOMAIN_RENDER, 0, 0);
+		ADVANCE_BATCH();
+
+		intel_batchbuffer_flush(batch);
+
+		drm_intel_bo_disable_reuse(load_bo);
+		drm_intel_bo_unreference(load_bo);
+	}
+
+	drm_intel_bufmgr_destroy(bufmgr);
+
+	close(fd);
+
+	return 0;
+}