[LTP] [PATCH v1] Add epoll_wait06 test

[Andrea Cervesato]

This test verifies EPOLLET functionality.

Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
 .../kernel/syscalls/epoll_wait/.gitignore     |  1 +
 .../kernel/syscalls/epoll_wait/epoll_wait06.c | 97 +++++++++++++++++++
 2 files changed, 98 insertions(+)
 create mode 100644 testcases/kernel/syscalls/epoll_wait/epoll_wait06.c

diff --git a/testcases/kernel/syscalls/epoll_wait/.gitignore b/testcases/kernel/syscalls/epoll_wait/.gitignore
index ab5a9c010..8c5ed7c5c 100644
--- a/testcases/kernel/syscalls/epoll_wait/.gitignore
+++ b/testcases/kernel/syscalls/epoll_wait/.gitignore
@@ -3,3 +3,4 @@ epoll_wait02
 epoll_wait03
 epoll_wait04
 epoll_wait05
+epoll_wait06
diff --git a/testcases/kernel/syscalls/epoll_wait/epoll_wait06.c b/testcases/kernel/syscalls/epoll_wait/epoll_wait06.c
new file mode 100644
index 000000000..ef3883e83
--- /dev/null
+++ b/testcases/kernel/syscalls/epoll_wait/epoll_wait06.c
@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2022 SUSE LLC Andrea Cervesato <andrea.cervesato@suse.com>
+ */
+
+/*\
+ * [Description]
+ *
+ * Verify that edge triggered behavior is correctly handled by epoll.
+ *
+ * [Algorithm]
+ * 
+ * 1. The file descriptor that represents the read side of a pipe (rfd) is
+ *    registered on the epoll instance.
+ * 2. A pipe writer writes 2 kB of data on the write side of the pipe.
+ * 3. A call to epoll_wait(2) is done that will return rfd as a ready file
+ *    descriptor.
+ * 4. The pipe reader reads 1 kB of data from rfd.
+ * 5. A call to epoll_wait(2) should fail because there's data left to read.
+ */
+
+#include <poll.h>
+#include <sys/epoll.h>
+#include "tst_test.h"
+
+#define WRITE_SIZE 2048
+#define READ_SIZE WRITE_SIZE / 2
+
+static int fds[2];
+static int epfd;
+
+static void cleanup(void)
+{
+	if (epfd > 0)
+		SAFE_CLOSE(epfd);
+
+	if (fds[0] > 0)
+		SAFE_CLOSE(fds[0]);
+
+	if (fds[1] > 0)
+		SAFE_CLOSE(fds[1]);
+}
+
+static void run(void)
+{
+	int res;
+	char buff[WRITE_SIZE];
+	struct epoll_event evt_receive;
+	struct epoll_event evt_request;
+
+	SAFE_PIPE(fds);
+
+	evt_request.events = EPOLLIN | EPOLLET;
+	evt_request.data.fd = fds[0];
+
+	epfd = epoll_create(2);
+	if (epfd == -1)
+		tst_brk(TBROK | TERRNO, "fail to create epoll instance");
+
+	tst_res(TINFO, "Polling channel with EPOLLET");
+
+	res = epoll_ctl(epfd, EPOLL_CTL_ADD, fds[0], &evt_request);
+	if (res == -1)
+		tst_brk(TBROK | TERRNO, "epoll_ctl failure");
+
+	tst_res(TINFO, "Write bytes on channel");
+
+	memset(buff, 'a', WRITE_SIZE);
+	SAFE_WRITE(0, fds[1], buff, WRITE_SIZE);
+
+	res = epoll_wait(epfd, &evt_receive, 1, 2000);
+	if (res <= 0) {
+		tst_res(TFAIL | TERRNO, "epoll_wait() returned %i", res);
+		goto close;
+	}
+
+	if ((evt_receive.events & EPOLLIN) == 0) {
+		tst_brk(TFAIL, "No data received");
+		goto close;
+	}
+
+	tst_res(TINFO, "Received EPOLLIN event. Read half bytes from channel");
+
+	memset(buff, 0, READ_SIZE);
+	SAFE_READ(1, evt_receive.data.fd, buff, READ_SIZE);
+
+	TST_EXP_EQ_LI(epoll_wait(epfd, &evt_receive, 1, 10), 0);
+
+close:
+	SAFE_CLOSE(fds[0]);
+	SAFE_CLOSE(fds[1]);
+}
+
+static struct tst_test test = {
+	.cleanup = cleanup,
+	.test_all = run,
+};
-- 
2.35.3