Re: [LTP] [PATCH v2 7/8] syscalls: Add epoll_wait12

[Andrea Cervesato via ltp <ltp@lists.linux.it>]

Hi Cyril,

> A test for EPOLLERR when we are waiting to write into a pipe and the
> read end is closed.
> 
> Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
> ---
>  runtest/syscalls                              |   1 +
>  .../kernel/syscalls/epoll_wait/.gitignore     |   1 +
>  .../kernel/syscalls/epoll_wait/epoll_wait12.c | 112 ++++++++++++++++++
>  3 files changed, 114 insertions(+)
>  create mode 100644 testcases/kernel/syscalls/epoll_wait/epoll_wait12.c
> 
> diff --git a/runtest/syscalls b/runtest/syscalls
> index c16cf3554..0787bbe72 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..eed395fcf
> --- /dev/null
> +++ b/testcases/kernel/syscalls/epoll_wait/epoll_wait12.c
> @@ -0,0 +1,112 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) Linux Test Project, 2026
> + */
> +
> +/*\
> + * Verify that 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 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 = poll(&pfd, 1, 0);

Why we don't have a SAFE_POLL() ? I just noticed how many times we are
following a manual errors handling pattern inside the tests.

> +		if (nfd == -1)
> +			tst_brk(TBROK | TERRNO, "poll()");
> +	} 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));

We have SAFE_EPOLL_WAIT(), is there a reason why not to use it?
Do we want to track the TST_RET ?

> +		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,
> +};
> -- 
> 2.52.0
> 
> 
> -- 
> Mailing list info: https://lists.linux.it/listinfo/ltp

Reviewed-by: Andrea Cervesato <andrea.cervesato@suse.com>

--
Andrea Cervesato
SUSE QE Automation Engineer Linux
andrea.cervesato@suse.com

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