[Intel-gfx] [PATCH i-g-t] i915/gem_mmap_gtt: Exercise many, many mappings of the same objects

[Chris Wilson]

Fork and remap the same object into a new process space under a new file
descriptor. Principally to check list management and find scaling issues
in using such lists.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Abdiel Janulgue <abdiel.janulgue at linux.intel.com>
---
 tests/i915/gem_mmap_gtt.c | 72 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 71 insertions(+), 1 deletion(-)

diff --git a/tests/i915/gem_mmap_gtt.c b/tests/i915/gem_mmap_gtt.c
index a5f9d934e..756940ca4 100644
--- a/tests/i915/gem_mmap_gtt.c
+++ b/tests/i915/gem_mmap_gtt.c
@@ -34,8 +34,9 @@
 #include <inttypes.h>
 #include <pthread.h>
 #include <errno.h>
-#include <sys/stat.h>
 #include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
 #include "drm.h"
 
 #include "igt.h"
@@ -323,6 +324,73 @@ test_pf_nonblock(int i915)
 	igt_spin_free(i915, spin);
 }
 
+static void
+test_fork_bomb(int i915)
+{
+	uint32_t *control;
+	uint32_t handle;
+	int dmabuf;
+
+	/* Rebind the same object into many different process adress spaces. */
+
+	control = mmap(NULL, 4096, PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0);
+	igt_assert(control != MAP_FAILED);
+
+	handle = gem_create(i915, 4096);
+	dmabuf = prime_handle_to_fd(i915, handle);
+	gem_close(i915, handle);
+
+	igt_fork(child, 1) {
+		int fd[512];
+
+		atomic_fetch_add(&control[1], 1);
+		while (!READ_ONCE(control[0])) {
+			int children;
+
+			atomic_fetch_add(&control[2], 1);
+
+			for (int i = 0; i < ARRAY_SIZE(fd); i++) {
+				fd[i] = gem_reopen_driver(i915);
+
+				handle = prime_fd_to_handle(fd[i], dmabuf);
+				gem_mmap__gtt(fd[i], handle, 4096, PROT_WRITE);
+				gem_close(fd[i], handle);
+
+				/* leave the fd + mmap for process cleanup */
+			}
+
+			for (children = 0; children < 2; children++) {
+				if (fork() > 0) { /* child */
+					atomic_fetch_add(&control[1], 1);
+					for (int i = 0; i < ARRAY_SIZE(fd); i++)
+						close(fd[i]);
+					break;
+				}
+			}
+			if (children == 2) { /* parent */
+				sched_yield();
+				break;
+			}
+		}
+		atomic_fetch_add(&control[1], -1);
+	}
+
+	sleep(30);
+
+	*control = 1;
+	igt_waitchildren();
+
+	while (READ_ONCE(control[1])) {
+		int status = 0;
+		wait(&status);
+	}
+
+	igt_info("Spawned %d children\n", control[2]);
+
+	close(dmabuf);
+	munmap(control, 4096);
+}
+
 static void
 test_isolation(int i915)
 {
@@ -1097,6 +1165,8 @@ igt_main
 		test_flink_race(fd);
 	igt_subtest("pf-nonblock")
 		test_pf_nonblock(fd);
+	igt_subtest("fork-bomb")
+		test_fork_bomb(fd);
 
 	igt_subtest("basic-small-bo")
 		test_huge_bo(fd, -1, I915_TILING_NONE);
-- 
2.24.0