diff --git a/action.sh b/action.sh
index 198f278b5..fc35ea781 100755
--- a/action.sh
+++ b/action.sh
@@ -28,7 +28,8 @@ case $cmd in
       kasan)
         ./run_tests.py --board $board --timeout=100 --times=50 --suite=$1 ;;
       kcsan)
-        ./run_tests.py --board $board --timeout=100 --times=50 --suite=$1
+        ./run_tests.py --board $board --timeout=100 --times=50 --suite=$1 \
+          --parallel=5
         # do not report it as failed because we have no people working on
         # fixing concurrency issues
         exit 0 ;;
diff --git a/run_tests.py b/run_tests.py
index fae371f0b..4b29e8368 100755
--- a/run_tests.py
+++ b/run_tests.py
@@ -24,17 +24,19 @@ def setup_terminal():
         subprocess.run(['stty', 'cols', str(cols), 'rows', str(rows)])
 
 
-def run_test(seed, board, timeout, suite=None):
-    print("Testing seed %u..." % seed)
+def run_test(seed, board, timeout, parallel, suite=None):
+    print('Testing seed %u...' % seed)
+
+    args = ['%s=all' % suite, 'seed=%u' % seed, 'repeat=%d' % REPEAT,
+            'parallel=%d' % parallel]
 
     try:
         launch = subprocess.Popen(
-                ['./launch', '--board', board, '-t', '--timeout=%d' % timeout,
-                 '%s=all' % suite, 'seed=%u' % seed, 'repeat=%d' % REPEAT])
+                ['./launch', '-b', board, '-t', '-T', str(timeout)] + args)
         rc = launch.wait()
         if rc:
-            print("Run `launch -d -b %s %s=all seed=%u repeat=%u` "
-                  "to reproduce the failure." % (board, suite, seed, REPEAT))
+            print('Run `launch -d -b %s %s` to reproduce the failure.' %
+                  (board, ' '.join(args)))
             sys.exit(rc)
     except KeyboardInterrupt:
         launch.send_signal(signal.SIGINT)
@@ -51,6 +53,8 @@ def run_test(seed, board, timeout, suite=None):
     parser.add_argument('-b', '--board', default='rpi3',
                         choices=['malta', 'rpi3', 'sifive_u'],
                         help='Emulated board.')
+    parser.add_argument('-p', '--parallel', type=int, default=1,
+                        help='Run at most N tests in parallel.')
     parser.add_argument('-s', '--suite', default='all',
                         choices=['all', 'user', 'kernel'],
                         help='Test suite to run.')
@@ -61,13 +65,10 @@ def run_test(seed, board, timeout, suite=None):
     # Run tests using n random seeds
     for _ in range(0, args.times):
         rand = random.randint(0, 2**32)
-        if args.suite == 'all':
-            run_test(rand, args.board, args.timeout, 'ktest')
-            run_test(rand, args.board, args.timeout, 'utest')
-        elif args.suite == 'kernel':
-            run_test(rand, args.board, args.timeout, 'ktest')
-        elif args.suite == 'user':
-            run_test(rand, args.board, args.timeout, 'utest')
-
-    print("Tests successful!")
+        if args.suite in ['all', 'kernel']:
+            run_test(rand, args.board, args.timeout, args.parallel, 'ktest')
+        if args.suite in ['all', 'user']:
+            run_test(rand, args.board, args.timeout, args.parallel, 'utest')
+
+    print('Tests successful!')
     sys.exit(0)