Bug 10985

Hi,

I have a fresh RH 6.2 installation on a dual-cpu P3.
simra@Chess:[simra] 3>rpm -q glibc
glibc-2.1.3-15
simra@Chess:[simra] 4>ls -l /lib/libpthread*
-rwxr-xr-x    1 root     root       289906 Feb 29 16:58
/lib/libpthread-0.8.so*
lrwxrwxrwx    1 root     root           17 Apr 17 17:46
/lib/libpthread.so.0 -> libpthread-0.8.so*
simra@Chess:[simra] 5>uname -a
Linux Chess.McRCIM.McGill.EDU 2.2.14-5.0smp #1 SMP Tue Mar 7 21:01:40
EST 2000 i686 unknown


The following short program works fine on a single processor machine,
but aborts on a dual.  I haven't tried it yet w/ open(2) and read(2), so
I'm not sure if it's a libc problem or kernel problem.  In any case it's
a serious problem.

btw, if I guard the inside of the while loop with a mutex, the same
problem occurs, so it seems to have something to do with the thread
migrating between processors (if this does indeed occur), and also suggests
that it's not a libc problem.



/************************************************************************
gcc -Wall -o threadtest -D_REENTRANT threadtest.c
-lpthread

Usage: ./threadtest

***********************************************************************/

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <string.h>

#define maxthreads 4
void * runthread(void* args);

int
main(int argc, char ** argv) {
  int t;
  pthread_t threads[maxthreads];

  t=0;
  for (t=0; t<maxthreads; t++) {
    fprintf(stderr,"Spawning thread %d\n", t);
    pthread_create(&threads[t], NULL,
                   runthread, argv[0]);
  }
  sleep(10000);
  exit(0);
}

void * runthread(void* args) {
  char buffer[1024];
  while (1) {
    FILE* fp=fopen("threadtest.c","r");
    if (!fp) {
      perror((char*)args);
      exit(1);
    }
    if (!fgets(buffer, 1023, fp)) {
      perror("Failed fgets");
      exit(1);
    }
    if (strncmp(buffer, "/*",2)) {
      fprintf(stderr, "Failed on *%s*\n",buffer);
      abort();
    } else fprintf(stderr,"%ld Success..\n",(long)fp);
    fclose(fp);
  }
  pthread_exit(0);
}