lib/drmtest: extract igt_fork from gem_concurrent_blt

Making sure that we correctly collect the exit codes from all children
is a bit a hassle. So add another magic igt codeblock for easy forking
and joining.

Note that children are (currently at least) not allowed to call igt_skip.
Add an assert to enforce this.

v2:
- Properly propagate the exit code.
- Fix the segfault.
- Add a child int and num_children paramter to the magic codeblock as
  suggested by Chris Wilson.
- Don't dump noise into stdout when a child thread fails, the parent
  will do that for us already.

v3: Now with some docs.

v4: Fixup igt_waitchildren to properly reset state so it can be used
again.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 24 insertions, 34 deletions

diff --git a/tests/gem_concurrent_blit.c b/tests/gem_concurrent_blit.c
index 69477748..b6d316d1 100644
--- a/tests/gem_concurrent_blit.c
+++ b/tests/gem_concurrent_blit.c
@@ -267,47 +267,37 @@ static void run_forked(struct access_mode *mode,
 		       do_test do_test_func)
 {
 	const int old_num_buffers = num_buffers;
-	pid_t children[16];
 
-	num_buffers /= ARRAY_SIZE(children);
+	num_buffers /= 16;
 	num_buffers += 2;
 
 	igt_fork_signal_helper();
 
-	for (int nc = 0; nc < ARRAY_SIZE(children); nc++) {
-		switch ((children[nc] = fork())) {
-		case -1: igt_assert(0);
-		default: break;
-		case 0:
-			 /* recreate process local variables */
-			 bufmgr = drm_intel_bufmgr_gem_init(fd, 4096);
-			 drm_intel_bufmgr_gem_enable_reuse(bufmgr);
-			 batch = intel_batchbuffer_alloc(bufmgr, intel_get_drm_devid(fd));
-			 for (int i = 0; i < num_buffers; i++) {
-				 src[i] = mode->create_bo(bufmgr, i, width, height);
-				 dst[i] = mode->create_bo(bufmgr, ~i, width, height);
-			 }
-			 dummy = mode->create_bo(bufmgr, 0, width, height);
-			 for (int loop = 0; loop < 10; loop++)
-				 do_test_func(mode, src, dst, dummy);
-			 /* as we borrow the fd, we need to reap our bo */
-			 for (int i = 0; i < num_buffers; i++) {
-				 drm_intel_bo_unreference(src[i]);
-				 drm_intel_bo_unreference(dst[i]);
-			 }
-			 drm_intel_bo_unreference(dummy);
-			 intel_batchbuffer_free(batch);
-			 drm_intel_bufmgr_destroy(bufmgr);
-			 exit(0);
+	igt_fork(child, 16) {
+		igt_fail(6);
+
+		/* recreate process local variables */
+		bufmgr = drm_intel_bufmgr_gem_init(fd, 4096);
+		drm_intel_bufmgr_gem_enable_reuse(bufmgr);
+		batch = intel_batchbuffer_alloc(bufmgr, intel_get_drm_devid(fd));
+		for (int i = 0; i < num_buffers; i++) {
+			src[i] = mode->create_bo(bufmgr, i, width, height);
+			dst[i] = mode->create_bo(bufmgr, ~i, width, height);
 		}
+		dummy = mode->create_bo(bufmgr, 0, width, height);
+		for (int loop = 0; loop < 10; loop++)
+			do_test_func(mode, src, dst, dummy);
+		/* as we borrow the fd, we need to reap our bo */
+		for (int i = 0; i < num_buffers; i++) {
+			drm_intel_bo_unreference(src[i]);
+			drm_intel_bo_unreference(dst[i]);
+		}
+		drm_intel_bo_unreference(dummy);
+		intel_batchbuffer_free(batch);
+		drm_intel_bufmgr_destroy(bufmgr);
 	}
-	for (int nc = 0; nc < ARRAY_SIZE(children); nc++) {
-		int status = -1;
-		while (waitpid(children[nc], &status, 0) == -1 &&
-		       errno == -EINTR)
-			;
-		igt_assert(status == 0);
-	}
+
+	igt_waitchildren();
 
 	igt_stop_signal_helper();