Limited to 255 threads in gdb 5.1 ?

[Andrew Burgess]

It seems that even if threads are exited and joined that once 255
have been created then no more can be created in gdb 5.1

Here is a test program. From the shell it runs to the tens of 
thousands of threads, in gdb I get:

athlon:ha > gdb -nx thtest
GNU gdb Red Hat Linux (5.1-2)
Copyright 2001 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and
you are
welcome to change it and/or distribute copies of it under certain
conditions.
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There is absolutely no warranty for GDB.  Type "show warranty" for
details.
This GDB was configured as "i386-redhat-linux"...
(gdb) run
Starting program: /v/src/ha/thtest 
[New Thread 1024 (LWP 10497)]
[New Thread 2049 (LWP 10554)]
[New Thread 1026 (LWP 10555)]
1 [New Thread 2051 (LWP 10556)]
2 [New Thread 3076 (LWP 10557)]
3 [New Thread 4101 (LWP 10558)]
4 [New Thread 5126 (LWP 10559)]
...
252 [New Thread 259326 (LWP 11578)]
253 [New Thread 260351 (LWP 11579)]
254 [New Thread 261376 (LWP 11580)]
255 
<stops here, I press ^C>
Program received signal SIGINT, Interrupt.
[Switching to Thread 1024 (LWP 10497)]
0x40071b85 in __sigsuspend (set=0xbfffed10) at
../sysdeps/unix/sysv/linux/sigsuspend.c:45
45      ../sysdeps/unix/sysv/linux/sigsuspend.c: No such file or
directory.
        in ../sysdeps/unix/sysv/linux/sigsuspend.c
(gdb) info threads
  2 Thread 2049 (LWP 10554)  0x4012d5c3 in __mmap () from
/lib/i686/libc.so.6
* 1 Thread 1024 (LWP 10497)  0x40071b85 in __sigsuspend
(set=0xbfffed10) at ../sysdeps/unix/sysv/linux/sigsuspend.c:45
(gdb) where
#0  0x40071b85 in __sigsuspend (set=0xbfffed10) at
../sysdeps/unix/sysv/linux/sigsuspend.c:45
#1  0x400371c9 in __pthread_wait_for_restart_signal (self=0x4003ff40)
at pthread.c:969
#2  0x4003729c in __pthread_create_2_1 (thread=0xbfffee94, attr=0x0,
start_routine=0x80485f0 <start>, arg=0x0)
    at restart.h:34
#3  0x08048628 in make ()
#4  0x080486a5 in main ()
#5  0x4005f627 in __libc_start_main (main=0x8048698 <main>, argc=1,
ubp_av=0xbfffef14, init=0x804841c <_init>,
    fini=0x80486f0 <_fini>, rtld_fini=0x4000dcc4 <_dl_fini>,
stack_end=0xbfffef0c) at ../sysdeps/generic/libc-start.c:129
(gdb) 

===============================================================
thtest.c:

/* recursively create threads until creation fails, then unwind the
recursion
and join all threads. Repeat.
*/

#include <stdio.h>
#include <pthread.h>

int count;

void *start(void *arg) {
        sleep(1);
        pthread_exit(NULL);
}

void make(void) {
        pthread_t t;
        int status = pthread_create(&t, NULL, start, NULL);
        switch(status) {
          case 0:
            break;
          default:
            return;
        }
        if(++count % 100) {
          printf("\r%d ", count);
          fflush(stdout);
        }
        make();
        pthread_join(t, NULL);
}

int main(int argc, char *argv[]) {
        while(1)
          make();
        return 0;
}