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Date: Wed, 14 May 2025 18:29:34 +0900
To: cygwin AT cygwin DOT com
Subject: FIFO hangs (Probably a bug of cygwin fifo)
Message-Id: <20250514182934.ee8ff6c46ecfc44c69e70b72@nifty.ne.jp>
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From: Takashi Yano via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>
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Sender: "Cygwin" <cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com>

Hi Ken,

I encountered the problem with fifo. The following STC hangs
in cygwin while it works in linux.

Perhaps, cygheap->fdtab.lock() causes a deadlock between
both open().

Could you please take a look?

#include <unistd.h>
#include <pthread.h>
#include <sys/stat.h>
#include <fcntl.h>

#define fifo1 "/tmp/fifo-test"

void *thr1(void *)
{
	int fd;
	usleep(100000);
	fd = open(fifo1, O_WRONLY);
	write(fd, "A", 1);
	usleep(100000);
	close(fd);
	return NULL;
}

int main()
{
	int fd;
	pthread_t th;
	char c;
	mkfifo(fifo1, 0600);
	pthread_create(&th, NULL, thr1, NULL);
	fd = open(fifo1, O_RDONLY);
	pthread_join(th, NULL);
	read(fd, &c, 1);
	write(1, &c, 1);
	close(fd);
	return 0;
}

-- 
Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>

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