executor: rework cgroups support

Turns out creating a cgroup per test is too expensive.
Moreover, it leads to hanged tasks as cgroup destruction
is asynchronous and overloads kernel work queues.

Create only a single cgroup per proc, but restrict
descriptions to mess with that single group,
instead test processes create own nested cgroups for messing.

1 files changed, 23 insertions, 32 deletions

diff --git a/pkg/csource/linux_common.go b/pkg/csource/linux_common.go
index 0c9d6571e..250b366d4 100644
--- a/pkg/csource/linux_common.go
+++ b/pkg/csource/linux_common.go
@@ -2698,6 +2698,29 @@ static void loop()
 	snprintf(cgroupdir_cpu, sizeof(cgroupdir_cpu), "/syzcgroup/cpu/syz%llu", procid);
 	char cgroupdir_net[64];
 	snprintf(cgroupdir_net, sizeof(cgroupdir_net), "/syzcgroup/net/syz%llu", procid);
+	if (mkdir(cgroupdir, 0777)) {
+		debug("mkdir(%s) failed: %d\n", cgroupdir, errno);
+	}
+	if (mkdir(cgroupdir_cpu, 0777)) {
+		debug("mkdir(%s) failed: %d\n", cgroupdir_cpu, errno);
+	}
+	if (mkdir(cgroupdir_net, 0777)) {
+		debug("mkdir(%s) failed: %d\n", cgroupdir_net, errno);
+	}
+	int pid = getpid();
+	char procs_file[128];
+	snprintf(procs_file, sizeof(procs_file), "%s/cgroup.procs", cgroupdir);
+	if (!write_file(procs_file, "%d", pid)) {
+		debug("write(%s) failed: %d\n", procs_file, errno);
+	}
+	snprintf(procs_file, sizeof(procs_file), "%s/cgroup.procs", cgroupdir_cpu);
+	if (!write_file(procs_file, "%d", pid)) {
+		debug("write(%s) failed: %d\n", procs_file, errno);
+	}
+	snprintf(procs_file, sizeof(procs_file), "%s/cgroup.procs", cgroupdir_net);
+	if (!write_file(procs_file, "%d", pid)) {
+		debug("write(%s) failed: %d\n", procs_file, errno);
+	}
 #endif
 	int iter;
 	for (iter = 0;; iter++) {
@@ -2707,17 +2730,6 @@ static void loop()
 		if (mkdir(cwdbuf, 0777))
 			fail("failed to mkdir");
 #endif
-#if defined(SYZ_EXECUTOR) || defined(SYZ_ENABLE_CGROUPS)
-		if (mkdir(cgroupdir, 0777)) {
-			debug("mkdir(%s) failed: %d\n", cgroupdir, errno);
-		}
-		if (mkdir(cgroupdir_cpu, 0777)) {
-			debug("mkdir(%s) failed: %d\n", cgroupdir_cpu, errno);
-		}
-		if (mkdir(cgroupdir_net, 0777)) {
-			debug("mkdir(%s) failed: %d\n", cgroupdir_net, errno);
-		}
-#endif
 #if defined(SYZ_EXECUTOR)
 		receive_execute(false);
 #endif
@@ -2745,16 +2757,6 @@ static void loop()
 			if (symlink(cgroupdir_net, "./cgroup.net")) {
 				debug("symlink(%s, ./cgroup.net) failed: %d\n", cgroupdir_net, errno);
 			}
-			int pid = getpid();
-			if (!write_file("./cgroup/cgroup.procs", "%d", pid)) {
-				debug("write(./cgroup/cgroup.procs) failed: %d\n", errno);
-			}
-			if (!write_file("./cgroup.cpu/cgroup.procs", "%d", pid)) {
-				debug("write(./cgroup.cpu/cgroup.procs) failed: %d\n", errno);
-			}
-			if (!write_file("./cgroup.net/cgroup.procs", "%d", pid)) {
-				debug("write(./cgroup.net/cgroup.procs) failed: %d\n", errno);
-			}
 #endif
 #if defined(SYZ_EXECUTOR)
 			if (flag_enable_tun) {
@@ -2815,17 +2817,6 @@ static void loop()
 #if defined(SYZ_EXECUTOR) || defined(SYZ_USE_TMP_DIR)
 		remove_dir(cwdbuf);
 #endif
-#if defined(SYZ_EXECUTOR) || defined(SYZ_ENABLE_CGROUPS)
-		if (rmdir(cgroupdir)) {
-			debug("rmdir(%s) failed: %d\n", cgroupdir, errno);
-		}
-		if (rmdir(cgroupdir_cpu)) {
-			debug("rmdir(%s) failed: %d\n", cgroupdir_cpu, errno);
-		}
-		if (rmdir(cgroupdir_net)) {
-			debug("rmdir(%s) failed: %d\n", cgroupdir_net, errno);
-		}
-#endif
 #if defined(SYZ_EXECUTOR) || defined(SYZ_RESET_NET_NAMESPACE)
 		reset_net_namespace();
 #endif