From mboxrd@z Thu Jan  1 00:00:00 1970
From: Cyril Hrubis <chrubis@suse.cz>
Date: Mon, 24 Feb 2020 13:58:02 +0100
Subject: [LTP] [PATCH] syscalls/pipe13: Add regression test for pipe to
 wake up all readers
In-Reply-To: <1582537946-22098-1-git-send-email-xuyang2018.jy@cn.fujitsu.com>
References: <1582537946-22098-1-git-send-email-xuyang2018.jy@cn.fujitsu.com>
Message-ID: <20200224125802.GA30073@rei.lan>
List-Id: <ltp.lists.linux.it>
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To: ltp@lists.linux.it

Hi!
> +static void verify_pipe(void)
> +{
> +	int fds[2];
> +	int status1, status2;
> +	pid_t p1, p2;
> +	int ret;
> +
> +	SAFE_PIPE(fds);
> +
> +	p1 = SAFE_FORK();
> +	if (p1 == 0) {
> +		SAFE_CLOSE(fds[1]);
> +		SAFE_READ(0, fds[0], &status1, sizeof(status1));
                                        ^
					Why status1 here?

					can't we just pass a dummy
					char buf; and size 1 here?

					It's not being written to
					anyways.
> +		exit(0);
> +	}
> +	p2 = SAFE_FORK();
> +	if (p2 == 0) {
> +		SAFE_CLOSE(fds[1]);
> +		SAFE_READ(0, fds[0], &status2, sizeof(status2));
                                      ^
				      Here as well.
> +		exit(0);
> +	}
> +
> +	sleep(1);

This sleep here has to be replaced by a proper synchronization given
that it's here to make sure both of the readers sleep on the pipe we
should:

* Use checkpoints to make sure both of the children have managed
  to get before the SAFE_READ().

* The the parent should use the TST_PROCESS_STATE_WAIT() to make sure
  both of the chidlren are sleeping

> +	SAFE_CLOSE(fds[1]);
> +
> +	SAFE_WAITPID(p1, &status1, 0);
> +	ret = waitpid(p2, &status2, WNOHANG);

We should just use waitpid with -1 as a pid here and WNOHANG twice,
because if one of the children hangs it's not guaranteed in any way
which one would that be.

> +	if (ret == p2) {
> +		tst_res(TPASS, "pipe wakes up everybody when last write closes");
> +	} else {
> +		tst_res(TFAIL, "pipe doesn't wake up every body when last write closes");
> +		SAFE_KILL(p2, SIGKILL);
> +		SAFE_WAIT(&status2);
> +	}
> +}
> +
> +static struct tst_test test = {
> +	.test_all = verify_pipe,
> +	.forks_child = 1,
> +	.tags = (const struct tst_tag[]) {
> +		{"linux-git", "6551d5c56eb"},
> +		{}
> +	}
> +};
> -- 
> 2.18.0
> 
> 
> 
> 
> -- 
> Mailing list info: https://lists.linux.it/listinfo/ltp

-- 
Cyril Hrubis
chrubis@suse.cz