src/hotspot/os/linux/waitBarrier_linux.cpp

rev 53038 : 8214271: Fast primitive to wake many threads
Reviewed-by:
rev 53039 : [mq]: 8214271-3

*** 36,49 ****
                 os::errno_name(err));                                        \
  } while (false)
  
  #define guarantee_with_errno(cond, msg) check_with_errno(guarantee, cond, msg)
  
! static int futex(volatile int *uaddr, int futex_op, int val,
!                  const struct timespec *timeout, int *uaddr2, int val3)
  {
!   return syscall(SYS_futex, uaddr, futex_op, val, timeout, uaddr2, val3);
  }
  
  void LinuxWaitBarrier::arm(int barrier_tag) {
    assert(_futex_barrier == 0, "Already armed");
    _futex_barrier = barrier_tag;
--- 36,48 ----
                 os::errno_name(err));                                        \
  } while (false)
  
  #define guarantee_with_errno(cond, msg) check_with_errno(guarantee, cond, msg)
  
! static int futex(volatile int *addr, int futex_op, int op_arg)
  {
!   return syscall(SYS_futex, addr, futex_op, op_arg, NULL, NULL, 0);
  }
  
  void LinuxWaitBarrier::arm(int barrier_tag) {
    assert(_futex_barrier == 0, "Already armed");
    _futex_barrier = barrier_tag;
*** 57,71 ****
  }
  
  void LinuxWaitBarrier::wake() {
    assert(_futex_barrier == 0, "Not disarmed");
    int s = futex(&_futex_barrier,
!                 FUTEX_WAKE,
!                 INT_MAX, /* wake a max of this many threads */
!                 NULL /* ignored */,
!                 NULL /* ignored */,
!                 0 /* ignored */);
    guarantee_with_errno(s > -1, "futex FUTEX_WAKE");
  }
  
  void LinuxWaitBarrier::wait(int barrier_tag) {
    assert(barrier_tag != 0, "Trying to wait on disarmed value");
--- 56,67 ----
  }
  
  void LinuxWaitBarrier::wake() {
    assert(_futex_barrier == 0, "Not disarmed");
    int s = futex(&_futex_barrier,
!                 FUTEX_WAKE_PRIVATE,
!                 INT_MAX /* wake a max of this many threads */);
    guarantee_with_errno(s > -1, "futex FUTEX_WAKE");
  }
  
  void LinuxWaitBarrier::wait(int barrier_tag) {
    assert(barrier_tag != 0, "Trying to wait on disarmed value");
*** 74,93 ****
      OrderAccess::fence();
      return;
    }
    do {
      int s = futex(&_futex_barrier,
!                   FUTEX_WAIT,
!                   barrier_tag, /* should be this tag */
!                   NULL, /* no timeout */
!                   NULL, /* ignored */
!                   0 /* ignored */);
      guarantee_with_errno((s == 0) ||
                           (s == -1 && errno == EAGAIN) ||
                           (s == -1 && errno == EINTR),
                           "futex FUTEX_WAIT");
!     // Return value 0, re-check in case of spurious wake-up.
!     // EINTR and re-check and go back to waiting.
!     // EAGAIN we already are disarmed, we should pass the check,
!     // if not re-armed with same tag.
    } while (barrier_tag == _futex_barrier);
  }
--- 70,85 ----
      OrderAccess::fence();
      return;
    }
    do {
      int s = futex(&_futex_barrier,
!                   FUTEX_WAIT_PRIVATE,
!                   barrier_tag /* should be this tag */);
      guarantee_with_errno((s == 0) ||
                           (s == -1 && errno == EAGAIN) ||
                           (s == -1 && errno == EINTR),
                           "futex FUTEX_WAIT");
!     // Return value 0: woken up, but re-check in case of spurious wakeup
!     // Error EINTR: woken by signal, so re-check and re-wait if necessary.
!     // Error EAGAIN: we are already disarmed and so will pass the check
    } while (barrier_tag == _futex_barrier);
  }