In the vhost-user-blk-test, as of now there is nothing stoping vhost-user-blk in QEMU writing to the socket right after forking off the storage daemon before it has a chance to come up properly, leaving the test hanging forever. This intermittently hanging test has caused QEMU automation failures reported multiple times on the mailing list [1].
This change makes the storage-daemon notify the vhost-user-blk-test that it is fully initialized and ready to handle client connections via a pipefd before allowing the test to proceed. This ensures that the storage-daemon backend won't miss vhost-user messages and thereby resolves the hang. [1] https://lore.kernel.org/qemu-devel/CAFEAcA8kYpz9LiPNxnWJAPSjc=nv532bedyfynabemeohqb...@mail.gmail.com/ Signed-off-by: Raphael Norwitz <raphael.norw...@nutanix.com> --- tests/qtest/vhost-user-blk-test.c | 33 ++++++++++++++++++++++++++++--- 1 file changed, 30 insertions(+), 3 deletions(-) diff --git a/tests/qtest/vhost-user-blk-test.c b/tests/qtest/vhost-user-blk-test.c index 6f108a1b62..b62af449df 100644 --- a/tests/qtest/vhost-user-blk-test.c +++ b/tests/qtest/vhost-user-blk-test.c @@ -21,6 +21,8 @@ #include "libqos/vhost-user-blk.h" #include "libqos/libqos-pc.h" +const char *daemon_msg = "Block exports setup\n"; + #define TEST_IMAGE_SIZE (64 * 1024 * 1024) #define QVIRTIO_BLK_TIMEOUT_US (30 * 1000 * 1000) #define PCI_SLOT_HP 0x06 @@ -885,7 +887,8 @@ static void start_vhost_user_blk(GString *cmd_line, int vus_instances, int num_queues) { const char *vhost_user_blk_bin = qtest_qemu_storage_daemon_binary(); - int i; + int i, err, pipe_fds[2]; + char buf[32] = {0}; gchar *img_path; GString *storage_daemon_command = g_string_new(NULL); QemuStorageDaemonState *qsd; @@ -898,6 +901,12 @@ static void start_vhost_user_blk(GString *cmd_line, int vus_instances, " -object memory-backend-memfd,id=mem,size=256M,share=on " " -M memory-backend=mem -m 256M "); + err = pipe(pipe_fds); + if (err != 0) { + fprintf(stderr, "start_vhost_user_blk: pipe() failed %m\n"); + abort(); + } + for (i = 0; i < vus_instances; i++) { int fd; char *sock_path = create_listen_socket(&fd); @@ -914,22 +923,40 @@ static void start_vhost_user_blk(GString *cmd_line, int vus_instances, i + 1, sock_path); } + g_string_append_printf(storage_daemon_command, "--printset"); + g_test_message("starting vhost-user backend: %s", storage_daemon_command->str); + pid_t pid = fork(); if (pid == 0) { + close(pipe_fds[0]); + /* * Close standard file descriptors so tap-driver.pl pipe detects when * our parent terminates. */ close(0); - close(1); open("/dev/null", O_RDONLY); - open("/dev/null", O_WRONLY); + close(1); + dup2(pipe_fds[1], 1); execlp("/bin/sh", "sh", "-c", storage_daemon_command->str, NULL); exit(1); } + + close(pipe_fds[1]); + + err = read(pipe_fds[0], buf, 20); + if (err < 0) { + fprintf(stderr, "Failed to read from storage-daemon pipe %m\n"); + abort(); + } else if (strcmp(buf, daemon_msg) != 0) { + fprintf(stderr, "qemu-storage-daemon did not write expected messaage " + "to the pipe. Total bytes read: %d. Got: %s\n", err, buf); + abort(); + } + g_string_free(storage_daemon_command, true); qsd = g_new(QemuStorageDaemonState, 1); -- 2.20.1
