linux-kernel - Re: [PATCH v2 2/2] selftests/nolibc: add testcase for pipe

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Date:   Tue, 01 Aug 2023 02:01:36 +0800
From:   Yuan Tan <tanyuan@...ylab.org>
To:     Thomas Weißschuh <thomas@...ch.de>
Cc:     w@....eu, falcon@...ylab.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, tanyuan@...ylab.org
Subject: Re: [PATCH v2 2/2] selftests/nolibc: add testcase for pipe

Hi Thomas,
On Mon, 2023-07-31 at 17:41 +0200, Thomas Weißschuh wrote:
> On 2023-07-31 20:35:28+0800, Yuan Tan wrote:
> > On Mon, 2023-07-31 at 08:10 +0200, Thomas Weißschuh wrote:
> > > On 2023-07-31 13:51:00+0800, Yuan Tan wrote:
> > > > Add a testcase of pipe that child process sends message to
> > > > parent
> > > > process.
> > > 
> > > Thinking about it some more:
> > > 
> > > What's the advantage of going via a child process?
> > > The pipe should work the same within the same process.
> > > 
> > 
> > The pipe is commonly used for process communication, and I think as
> > a
> > test case it is supposed to cover the most common scenarios.
> 
> The testcase is supposed to cover the code of nolibc.
> It should be the *minimal* amount of code to be reasonable sure that
> the
> code in nolibc does the correct thing.
> If pipe() returns a value that behaves like a pipe I see no reason to
> doubt it will also survive fork().
> 
> Validating that would mean testing the kernel and not nolibc.
> For the kernel there are different testsuites.
> 
> Less code means less work for everyone involved, now and in the
> future.
> 

It's a good point and I never thought about this aspect.

I wonder whether the code below is enough?

static int test_pipe(void)
{
	int pipefd[2];

	if (pipe(pipefd) == -1)
		return 1;

	close(pipefd[0]);
	close(pipefd[1]);

	return 0;
}

And I forgot to add this line:

	CASE_TEST(pipe); EXPECT_SYSZR(1, test_pipe()); break;

I will add it in next patch.