Merge branch 'vsock-test-improve-sigpipe-test-reliability'

Stefano Garzarella says:

====================
vsock/test: improve sigpipe test reliability

Running the tests continuously I noticed that sometimes the sigpipe
test would fail due to a race between the control message of the test
and the vsock transport messages.

While I was at it I also improved the test by checking the errno we
expect.

v1: https://lore.kernel.org/20250508142005.135857-1-sgarzare@redhat.com
====================

Link: https://patch.msgid.link/20250514141927.159456-1-sgarzare@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 57 insertions, 8 deletions

diff --git a/tools/testing/vsock/timeout.c b/tools/testing/vsock/timeout.c
index 44aee49b6cee..1453d38e08bb 100644
--- a/tools/testing/vsock/timeout.c
+++ b/tools/testing/vsock/timeout.c
@@ -21,6 +21,7 @@
 #include <stdbool.h>
 #include <unistd.h>
 #include <stdio.h>
+#include <time.h>
 #include "timeout.h"
 
 static volatile bool timeout;
@@ -28,6 +29,8 @@ static volatile bool timeout;
 /* SIGALRM handler function.  Do not use sleep(2), alarm(2), or
  * setitimer(2) while using this API - they may interfere with each
  * other.
+ *
+ * If you need to sleep, please use timeout_sleep() provided by this API.
  */
 void sigalrm(int signo)
 {
@@ -58,3 +61,18 @@ void timeout_end(void)
 	alarm(0);
 	timeout = false;
 }
+
+/* Sleep in a timeout section.
+ *
+ * nanosleep(2) can be used with this API since POSIX.1 explicitly
+ * specifies that it does not interact with signals.
+ */
+int timeout_usleep(useconds_t usec)
+{
+	struct timespec ts = {
+		.tv_sec = usec / 1000000,
+		.tv_nsec = (usec % 1000000) * 1000,
+	};
+
+	return nanosleep(&ts, NULL);
+}
diff --git a/tools/testing/vsock/timeout.h b/tools/testing/vsock/timeout.h
index ecb7c840e65a..1c3fcad87a49 100644
--- a/tools/testing/vsock/timeout.h
+++ b/tools/testing/vsock/timeout.h
@@ -11,5 +11,6 @@ void sigalrm(int signo);
 void timeout_begin(unsigned int seconds);
 void timeout_check(const char *operation);
 void timeout_end(void);
+int timeout_usleep(useconds_t usec);
 
 #endif /* TIMEOUT_H */
diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
index 613551132a96..9ea33b78b9fc 100644
--- a/tools/testing/vsock/vsock_test.c
+++ b/tools/testing/vsock/vsock_test.c
@@ -1058,18 +1058,39 @@ static void sigpipe(int signo)
 	have_sigpipe = 1;
 }
 
+#define SEND_SLEEP_USEC (10 * 1000)
+
 static void test_stream_check_sigpipe(int fd)
 {
 	ssize_t res;
 
 	have_sigpipe = 0;
 
-	res = send(fd, "A", 1, 0);
-	if (res != -1) {
-		fprintf(stderr, "expected send(2) failure, got %zi\n", res);
-		exit(EXIT_FAILURE);
+	/* When the other peer calls shutdown(SHUT_RD), there is a chance that
+	 * the send() call could occur before the message carrying the close
+	 * information arrives over the transport. In such cases, the send()
+	 * might still succeed. To avoid this race, let's retry the send() call
+	 * a few times, ensuring the test is more reliable.
+	 */
+	timeout_begin(TIMEOUT);
+	while(1) {
+		res = send(fd, "A", 1, 0);
+		if (res == -1 && errno != EINTR)
+			break;
+
+		/* Sleep a little before trying again to avoid flooding the
+		 * other peer and filling its receive buffer, causing
+		 * false-negative.
+		 */
+		timeout_usleep(SEND_SLEEP_USEC);
+		timeout_check("send");
 	}
+	timeout_end();
 
+	if (errno != EPIPE) {
+		fprintf(stderr, "unexpected send(2) errno %d\n", errno);
+		exit(EXIT_FAILURE);
+	}
 	if (!have_sigpipe) {
 		fprintf(stderr, "SIGPIPE expected\n");
 		exit(EXIT_FAILURE);
@@ -1077,12 +1098,21 @@ static void test_stream_check_sigpipe(int fd)
 
 	have_sigpipe = 0;
 
-	res = send(fd, "A", 1, MSG_NOSIGNAL);
-	if (res != -1) {
-		fprintf(stderr, "expected send(2) failure, got %zi\n", res);
-		exit(EXIT_FAILURE);
+	timeout_begin(TIMEOUT);
+	while(1) {
+		res = send(fd, "A", 1, MSG_NOSIGNAL);
+		if (res == -1 && errno != EINTR)
+			break;
+
+		timeout_usleep(SEND_SLEEP_USEC);
+		timeout_check("send");
 	}
+	timeout_end();
 
+	if (errno != EPIPE) {
+		fprintf(stderr, "unexpected send(2) errno %d\n", errno);
+		exit(EXIT_FAILURE);
+	}
 	if (have_sigpipe) {
 		fprintf(stderr, "SIGPIPE not expected\n");
 		exit(EXIT_FAILURE);