selftests/xsk: fix timeout thread harness sequencing

Prevent workers from running before XDP program attachment completes.
The previous ordering allowed races between worker startup and setup.

Attach XDP programs before entering traffic validation.

Remove SIGUSR1-based worker termination and use pthread_join() for
thread shutdown so blocking syscalls are not interrupted.

Use barriers only for dual-thread runs so participants match and
teardown ordering stays deterministic.

This removes setup/startup races and stabilizes harness sequencing.

Signed-off-by: Tushar Vyavahare <tushar.vyavahare@intel.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://patch.msgid.link/20260616154955.1492560-3-tushar.vyavahare@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 18 insertions, 16 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/test_xsk.c b/tools/testing/selftests/bpf/prog_tests/test_xsk.c
index ca47a16ceb1a..d4702d2aac5e 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_xsk.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_xsk.c
@@ -7,7 +7,6 @@
 #include <linux/netdev.h>
 #include <poll.h>
 #include <pthread.h>
-#include <signal.h>
 #include <string.h>
 #include <sys/mman.h>
 #include <sys/socket.h>
@@ -1671,7 +1670,8 @@ void *worker_testapp_validate_rx(void *arg)
 				       strerror(-err));
 	}
 
-	pthread_barrier_wait(&barr);
+	if (test->use_barrier)
+		pthread_barrier_wait(&barr);
 
 	/* We leave only now in case of error to avoid getting stuck in the barrier */
 	if (err) {
@@ -1710,11 +1710,6 @@ static void testapp_clean_xsk_umem(struct ifobject *ifobj)
 	munmap(umem->buffer, umem->mmap_size);
 }
 
-static void handler(int signum)
-{
-	pthread_exit(NULL);
-}
-
 static bool xdp_prog_changed_rx(struct test_spec *test)
 {
 	struct ifobject *ifobj = test->ifobj_rx;
@@ -1819,9 +1814,18 @@ static int __testapp_validate_traffic(struct test_spec *test, struct ifobject *i
 		return TEST_FAILURE;
 	}
 
-	if (ifobj2) {
+	err = xsk_attach_xdp_progs(test, ifobj1, ifobj2);
+	if (err) {
+		ksft_print_msg("Error: failed to attach XDP programs: %d (%s)\n",
+			       err, strerror(-err));
+		return TEST_FAILURE;
+	}
+	test->use_barrier = !!ifobj2;
+
+	if (test->use_barrier) {
 		if (pthread_barrier_init(&barr, NULL, 2))
 			return TEST_FAILURE;
+
 		pkt_stream_reset(ifobj2->xsk->pkt_stream);
 	}
 
@@ -1829,27 +1833,26 @@ static int __testapp_validate_traffic(struct test_spec *test, struct ifobject *i
 	pkt_stream_reset(ifobj1->xsk->pkt_stream);
 	pkts_in_flight = 0;
 
-	signal(SIGUSR1, handler);
 	/*Spawn RX thread */
 	pthread_create(&t0, NULL, ifobj1->func_ptr, test);
 
-	if (ifobj2) {
+	if (test->use_barrier) {
 		pthread_barrier_wait(&barr);
 		if (pthread_barrier_destroy(&barr)) {
-			pthread_kill(t0, SIGUSR1);
+			test->use_barrier = false;
+			pthread_join(t0, NULL);
 			clean_sockets(test, ifobj1);
 			clean_umem(test, ifobj1, NULL);
 			return TEST_FAILURE;
 		}
+	}
 
+	if (ifobj2) {
 		/*Spawn TX thread */
 		pthread_create(&t1, NULL, ifobj2->func_ptr, test);
-
 		pthread_join(t1, NULL);
 	}
 
-	if (!ifobj2)
-		pthread_kill(t0, SIGUSR1);
 	pthread_join(t0, NULL);
 
 	if (test->total_steps == test->current_step || test->fail) {
@@ -1887,8 +1890,6 @@ static int testapp_validate_traffic(struct test_spec *test)
 		}
 	}
 
-	if (xsk_attach_xdp_progs(test, ifobj_rx, ifobj_tx))
-		return TEST_FAILURE;
 	return __testapp_validate_traffic(test, ifobj_rx, ifobj_tx);
 }
 
diff --git a/tools/testing/selftests/bpf/prog_tests/test_xsk.h b/tools/testing/selftests/bpf/prog_tests/test_xsk.h
index 20eaaa254998..03753ddc5dcd 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_xsk.h
+++ b/tools/testing/selftests/bpf/prog_tests/test_xsk.h
@@ -208,6 +208,7 @@ struct test_spec {
 	bool adjust_tail;
 	bool adjust_tail_support;
 	bool poll_tmout;
+	bool use_barrier;
 	enum test_mode mode;
 	char name[MAX_TEST_NAME_SIZE];
 };