The following Program, compiled and ran under RH7 with glibc 2.1.94-3 and a
2.2 kernel, failes. The same prog compiled and ran under RH6.2, glibc
2.1.2-11 works perfectly.

The Program:

#define _FILE_OFFSET_BITS 64

#include <stdio.h>
#include <fcntl.h>
#include <errno.h>

int main()
{
  struct flock  plockb;
  int           lock_failed;
  int           fd;

  fd = open("test", O_RDWR | O_CREAT, 0644);

  plockb.l_type = F_WRLCK;
  plockb.l_whence = SEEK_SET;
  plockb.l_start=0;
  plockb.l_len=0;

  lock_failed = fcntl(fd, F_SETLK, &plockb);

  if(lock_failed)
  {
        printf("errno: %i string: %s\n",errno,strerror(errno));
  }
  else
  {
        printf("success\n");
  } 

  close(fd);

}

strace with RH7:

open("test", O_RDWR|O_CREAT|O_LARGEFILE, 0644) = 3
fcntl64(3, 0xd /* F_??? */, 0xbffffb10) = -1 ENOSYS (Function not
implemented)
fcntl(3, 0xd /* F_??? */, 0xbffffaa0)   = -1 EINVAL (Invalid argument)

strace with RH6.2:

open("test", O_RDWR|O_CREAT|O_LARGEFILE, 0644) = 3
fcntl(3, F_SETLK, {type=F_WRLCK, whence=SEEK_SET, start=0, len=0}) = 0