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Date: Fri, 13 May 2005 20:06:43 -0400
From: Jakub Jelinek <jakub@redhat.com>
To: ritesh@cs.unc.edu
Cc: Linux Kernel Development <linux-kernel@vger.kernel.org>
Subject: Re: NPTL: stack limit limiting number of threads
Message-ID: <20050514000643.GI17420@devserv.devel.redhat.com>
Reply-To: Jakub Jelinek <jakub@redhat.com>
References: <fc67f8b705051312494a0badf7@mail.gmail.com> <20050513202346.GG17420@devserv.devel.redhat.com> <fc67f8b705051317023859c443@mail.gmail.com>
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On Fri, May 13, 2005 at 08:02:48PM -0400, Ritesh Kumar wrote:
>     Thanks for your reply. I actually went ahead after getting your
> mail and coded up a small program to check the stack limit
> deliberately. The program is shown inline.
> 
> #include <stdio.h>
> 
> #define BUF_SIZE 1024000
> 
> void recurse(int n){
> 	char ch[BUF_SIZE];
> 	if(n<=0)
> 		return;
> 	else
> 		recurse(n-1);
> }
> 
> int main(argc, argv)
> 	int argc;
> 	char **argv;
> {
> 	if(argc!=2){
> 		printf("Usage: %s <n (megabytes)>\n", argv[0]);
> 		return 1;
> 	}
> 	printf("Checking for %dMB\n", atoi(argv[1]));
> 	recurse(atoi(argv[1]));
> }
> 
> Its a fairly crude way to find out the actual stack limit. Basically,
> the resurse function recurses each time allocating ~1MB of space on
> the stack. The program segfaults exactly at the ulimit -s value of
> stack size on both linux and freebsd. So it does seem that the ulimit
> -s is the value of stack limit used on FreeBSD.

For the main stack sure.  But now try to call that recurse in
some other thread.

	Jakub
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