[LTP] [PATCH v1] Add regression test for hangup on pipe operations

[Richard Palethorpe]

Hello,

Pushed with some significant changes, please see commit for
details. Thanks!

Marius Kittler <mkittler@suse.de> writes:

> This tests the problem fixed by the patch
> https://www.spinics.net/lists/linux-api/msg49731.html.
>
> Signed-off-by: Marius Kittler <mkittler@suse.de>
> ---
>  runtest/syscalls                          |  1 +
>  testcases/kernel/syscalls/pipe/.gitignore |  1 +
>  testcases/kernel/syscalls/pipe/pipe15.c   | 96 +++++++++++++++++++++++
>  3 files changed, 98 insertions(+)
>  create mode 100644 testcases/kernel/syscalls/pipe/pipe15.c
>
> diff --git a/runtest/syscalls b/runtest/syscalls
> index 4f1ee1f34..6c125c2f5 100644
> --- a/runtest/syscalls
> +++ b/runtest/syscalls
> @@ -1004,6 +1004,7 @@ pipe11 pipe11
>  pipe12 pipe12
>  pipe13 pipe13
>  pipe14 pipe14
> +pipe15 pipe15
>  
>  pipe2_01 pipe2_01
>  pipe2_02 pipe2_02
> diff --git a/testcases/kernel/syscalls/pipe/.gitignore b/testcases/kernel/syscalls/pipe/.gitignore
> index 774d73205..581a68b78 100644
> --- a/testcases/kernel/syscalls/pipe/.gitignore
> +++ b/testcases/kernel/syscalls/pipe/.gitignore
> @@ -12,3 +12,4 @@
>  /pipe12
>  /pipe13
>  /pipe14
> +/pipe15
> diff --git a/testcases/kernel/syscalls/pipe/pipe15.c b/testcases/kernel/syscalls/pipe/pipe15.c
> new file mode 100644
> index 000000000..7b55143c1
> --- /dev/null
> +++ b/testcases/kernel/syscalls/pipe/pipe15.c
> @@ -0,0 +1,96 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) 2023 SUSE LLC Marius Kittler <mkittler@suse.de>
> + */
> +
> +/*\
> + * [Description]
> + *
> + * This is a regression test for hangup on pipe operations. See
> + * https://www.spinics.net/lists/linux-api/msg49762.html for
> + * additional context. It tests that pipe operations do not block
> + * indefinitely when going to the soft limit on the total size of
> + * all pipes created by a single user.
> + */
> +
> +#define _GNU_SOURCE
> +#include <fcntl.h>
> +#include <stdlib.h>
> +#include <unistd.h>
> +
> +#include "tst_test.h"
> +#include "tst_safe_stdio.h"
> +#include "tst_safe_macros.h"
> +
> +static int pipe_count;
> +static int *pipes;
> +static char *buffer;
> +static int buffer_size;
> +
> +static void run(void)
> +{
> +	SAFE_WRITE(0, pipes[1], buffer, buffer_size);
> +	SAFE_READ(0, pipes[0], buffer, buffer_size - 1);
> +	SAFE_WRITE(0, pipes[1], buffer, 1);
> +	tst_res(TPASS,
> +		"Pipe operations do not block indefinitely when going to "
> +		"the soft limit on the total size of all pipes created by "
> +		"a single user");
> +}
> +
> +static void setup(void)
> +{
> +	int pipe[2];
> +	int page_size = getpagesize(), soft_limit;
> +	struct rlimit nfd;
> +
> +	/* determine the buffer size of a pipe, usually 65536 */
> +	SAFE_PIPE(pipe);
> +	buffer_size = fcntl(pipe[1], F_GETPIPE_SZ);
> +	SAFE_CLOSE(pipe[0]);
> +	SAFE_CLOSE(pipe[1]);
> +
> +	/* determine the max number of pipes we can create within the
> +	 * soft limit, usually 1024
> +	 */
> +	SAFE_FILE_SCANF("/proc/sys/fs/pipe-user-pages-soft", "%i", &soft_limit);
> +	pipe_count = soft_limit * page_size / buffer_size;
> +
> +	tst_res(TINFO, "Soft limit for pipes: %i pages", soft_limit);
> +	tst_res(TINFO, "Buffer size: %d byte", buffer_size);
> +	tst_res(TINFO, "Creating %i pipes", pipe_count);
> +
> +	/* avoid running into "pipe() failed: EMFILE (24)" */
> +	SAFE_GETRLIMIT(RLIMIT_NOFILE, &nfd);
> +	if (nfd.rlim_max < (unsigned long)pipe_count)
> +		tst_brk(TCONF, "NOFILE limit max too low: %lu < %i",
> +			nfd.rlim_max, pipe_count);
> +	if (nfd.rlim_cur < nfd.rlim_max) {
> +		nfd.rlim_cur = nfd.rlim_max;
> +		SAFE_SETRLIMIT(RLIMIT_NOFILE, &nfd);
> +	}
> +
> +	/* allocate memory for pipes and the buffer */
> +	pipes = calloc(pipe_count * 2, sizeof(int));
> +	memset(pipes, 0xFF, pipe_count * 2 * sizeof(int));
> +	for (int i = 0; i < pipe_count; ++i)
> +		SAFE_PIPE(pipes + i * 2);
> +	buffer = calloc(buffer_size, 1);
> +}
> +
> +static void cleanup(void)
> +{
> +	for (int i = 0; i < pipe_count * 2; i++)
> +		if (pipes[i] > 0)
> +			SAFE_CLOSE(pipes[i]);
> +	if (pipes)
> +		free(pipes);
> +	if (buffer)
> +		free(buffer);
> +}
> +
> +static struct tst_test test = {
> +	.setup = setup,
> +	.test_all = run,
> +	.cleanup = cleanup
> +};
> -- 
> 2.42.0


-- 
Thank you,
Richard.