executor: ignore async flag in the non-threaded mode

pkg/repro tries to clear the Threaded flag during repro simplification,
so it's easier just to ignore the remaining async flags in that case -
they won't be in the C repro either.

Add a test to pkg/ipc to verify the new behavior.

1 files changed, 3 insertions, 3 deletions

diff --git a/executor/executor.cc b/executor/executor.cc
index c0e2e6625..73f6053ee 100644
--- a/executor/executor.cc
+++ b/executor/executor.cc
@@ -871,10 +871,10 @@ void execute_one()
 		thread_t* th = schedule_call(call_index++, call_num, copyout_index,
 					     num_args, args, input_pos, call_props);
 
-		if (call_props.async) {
-			if (!flag_threaded)
-				fail("SYZFAIL: unable to do an async call in a non-threaded mode");
+		if (call_props.async && flag_threaded) {
 			// Don't wait for an async call to finish. We'll wait at the end.
+			// If we're not in the threaded mode, just ignore the async flag - during repro simplification syzkaller
+			// will anyway try to make it non-threaded.
 		} else if (flag_threaded) {
 			// Wait for call completion.
 			uint64 timeout_ms = syscall_timeout_ms + call->attrs.timeout * slowdown_scale;