[PATCH v3 8/9] syscalls: Add epoll_wait12

A test for EPOLLERR when we are waiting to write into a pipe and the
read end is closed.

Signed-off-by: Cyril Hrubis <[email protected]>
Reviewed-by: Andrea Cervesato <andrea.cervesato-IBi9RG/[email protected]>
---
 runtest/syscalls                              |   1 +
 .../kernel/syscalls/epoll_wait/.gitignore     |   1 +
 .../kernel/syscalls/epoll_wait/epoll_wait12.c | 111 ++++++++++++++++++
 3 files changed, 113 insertions(+)
 create mode 100644 testcases/kernel/syscalls/epoll_wait/epoll_wait12.c

diff --git a/runtest/syscalls b/runtest/syscalls
index 269fc162a..ec4907212 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -200,6 +200,7 @@ epoll_wait08 epoll_wait08
 epoll_wait09 epoll_wait09
 epoll_wait10 epoll_wait10
 epoll_wait11 epoll_wait11
+epoll_wait12 epoll_wait12
 
 epoll_pwait01 epoll_pwait01
 epoll_pwait02 epoll_pwait02
diff --git a/testcases/kernel/syscalls/epoll_wait/.gitignore b/testcases/kernel/syscalls/epoll_wait/.gitignore
index 57bdf0806..ad890d077 100644
--- a/testcases/kernel/syscalls/epoll_wait/.gitignore
+++ b/testcases/kernel/syscalls/epoll_wait/.gitignore
@@ -9,3 +9,4 @@ epoll_wait08
 epoll_wait09
 epoll_wait10
 epoll_wait11
+epoll_wait12
diff --git a/testcases/kernel/syscalls/epoll_wait/epoll_wait12.c b/testcases/kernel/syscalls/epoll_wait/epoll_wait12.c
new file mode 100644
index 000000000..819e908f4
--- /dev/null
+++ b/testcases/kernel/syscalls/epoll_wait/epoll_wait12.c
@@ -0,0 +1,111 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2026 Cyril Hrubis <[email protected]>
+ */
+
+/*\
+ * Verify that :manpage:epoll_wait() reports EPOLLERR when the read end of a
+ * pipe is closed while a child process is blocked in epoll_wait on the write
+ * end.
+ *
+ * [Algorithm]
+ *
+ * - Create a pipe and fill it completely so the write end is not writable.
+ * - Register the write end with an epoll instance for EPOLLOUT.
+ * - Fork a child that closes its copy of the read end and blocks in
+ *   epoll_wait waiting for the pipe to become writable.
+ * - Parent waits for the child to enter sleep state, then closes the read
+ *   end.
+ * - The child's :manpage:epoll_wait() should return with EPOLLERR set.
+ */
+
+#include <sys/epoll.h>
+#include <poll.h>
+
+#include "tst_test.h"
+#include "tst_epoll.h"
+
+static int efd = -1, fds[2] = {-1, -1};
+
+static void fill_pipe(int fd)
+{
+	char buf[4096];
+	struct pollfd pfd = {.fd = fd, .events = POLLOUT};
+	int nfd;
+
+	memset(buf, 'a', sizeof(buf));
+
+	do {
+		SAFE_WRITE(SAFE_WRITE_ANY, fd, buf, sizeof(buf));
+		nfd = SAFE_POLL(&pfd, 1, 0);
+	} while (nfd > 0);
+}
+
+static void run(void)
+{
+	pid_t pid;
+
+	SAFE_PIPE(fds);
+	fill_pipe(fds[1]);
+
+	efd = SAFE_EPOLL_CREATE1(0);
+
+	struct epoll_event ev = {
+		.events = EPOLLOUT,
+		.data.fd = fds[1],
+	};
+
+	SAFE_EPOLL_CTL(efd, EPOLL_CTL_ADD, fds[1], &ev);
+
+	pid = SAFE_FORK();
+	if (!pid) {
+		SAFE_CLOSE(fds[0]);
+
+		TEST(epoll_wait(efd, &ev, 1, 5000));
+		if (TST_RET != 1) {
+			tst_res(TFAIL | TTERRNO,
+				"epoll_wait() returned %li, expected 1",
+				TST_RET);
+			exit(0);
+		}
+
+		if (ev.data.fd != fds[1]) {
+			tst_res(TFAIL, "epoll.data.fd %d, expected %d",
+				ev.data.fd, fds[1]);
+			exit(0);
+		}
+
+		if (!(ev.events & EPOLLERR)) {
+			tst_res(TFAIL, "events %x, EPOLLERR not set",
+				ev.events);
+			exit(0);
+		}
+
+		tst_res(TPASS,
+			"epoll_wait() reported EPOLLERR on broken pipe");
+		exit(0);
+	}
+
+	TST_PROCESS_STATE_WAIT(pid, 'S', 0);
+	SAFE_CLOSE(fds[0]);
+	SAFE_CLOSE(fds[1]);
+	SAFE_CLOSE(efd);
+}
+
+static void cleanup(void)
+{
+	if (fds[1] != -1)
+		SAFE_CLOSE(fds[1]);
+
+	if (fds[0] != -1)
+		SAFE_CLOSE(fds[0]);
+
+	if (efd != -1)
+		SAFE_CLOSE(efd);
+}
+
+static struct tst_test test = {
+	.test_all = run,
+	.cleanup = cleanup,
+	.forks_child = 1,
+};
-- 
2.53.0


-- 
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