Re: [PATCH v2] pipe: fix SSH hang (again)

[Takashi Yano]

On Wed, 25 Jun 2025 19:55:34 +0900
Takashi Yano wrote:
> Hi Johannes,
> 
> On Wed, 25 Jun 2025 09:38:17 +0200 (CEST)
> Johannes Schindelin wrote:
> > Hi Takashi,
> > 
> > On Wed, 25 Jun 2025, Johannes Schindelin wrote:
> > 
> > > On Wed, 25 Jun 2025, Takashi Yano wrote:
> > > 
> > > > I'd revise the patch as follows. Could you please test if the
> > > > following patch also solves the issue?
> > > 
> > > Will do.
> > 
> > For the record, in my tests, this fixed the hangs, too.
> 
> Thanks for testing.
> However, I noticed that this patch changes the behavior Corinna was
> concerned about.

The behaviour change can be checked using attached test case.

-- 
Takashi Yano <takashi.y...@nifty.ne.jp>

#include <unistd.h>
#include <stdio.h>
#include <limits.h>
#include <fcntl.h>

#define PIPE_SIZE 65536

int main()
{
	int fd[2];
	char buf[PIPE_SIZE];
	int flags;

	pipe(fd);

	/* Set non-blocking */
	flags = fcntl(fd[1], F_GETFL);
	flags |= O_NONBLOCK;
	fcntl(fd[1], F_SETFL, flags);

	/* Fill pipe */
	printf("w:%d\n", write(fd[1], buf, PIPE_SIZE));
	/* Free PIPE_BUF/2 bytes */
	printf("r:%d\n", read(fd[0], buf, PIPE_BUF/2));

	/* Write PIPE_BUF bytes */
	printf("w:%d\n", write(fd[1], buf, 1));
	printf("w:%d\n", write(fd[1], buf, PIPE_BUF-1));
	printf("w:%d\n", write(fd[1], buf, PIPE_BUF));
	printf("w:%d\n", write(fd[1], buf, PIPE_BUF+1));
	printf("w:%d\n", write(fd[1], buf, PIPE_BUF*2));
	printf("w:%d\n", write(fd[1], buf, PIPE_BUF*2));
	printf("w:%d\n", write(fd[1], buf, PIPE_BUF*2));
	printf("w:%d\n", write(fd[1], buf, PIPE_BUF*2));
	printf("w:%d\n", write(fd[1], buf, PIPE_BUF*2));
	printf("w:%d\n", write(fd[1], buf, PIPE_BUF*2));

	return 0;
}