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Date: Thu, 15 May 2025 18:18:26 -0400
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Subject: Re: FIFO hangs (Probably a bug of cygwin fifo)
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From: Ken Brown via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Ken Brown <kbrown AT cornell DOT edu>
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Hi Takashi,

On 5/14/2025 5:29 AM, Takashi Yano via Cygwin wrote:
> 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;
> }
> 

Thanks for the STC.  I can reproduce the problem.  I'll take a look.

Ken

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