src/share/vm/runtime/safepoint.cpp

*** 262,273 ****
        // Blocking or yielding incur their own penalties in the form of context switching
        // and the resultant loss of $ residency.
        //
        // Further complicating matters is that yield() does not work as naively expected
        // on many platforms -- yield() does not guarantee that any other ready threads
!       // will run.   As such we revert yield_all() after some number of iterations.
!       // Yield_all() is implemented as a short unconditional sleep on some platforms.
        // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
        // can actually increase the time it takes the VM thread to detect that a system-wide
        // stop-the-world safepoint has been reached.  In a pathological scenario such as that
        // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
        // In that case the mutators will be stalled waiting for the safepoint to complete and the
--- 262,273 ----
        // Blocking or yielding incur their own penalties in the form of context switching
        // and the resultant loss of $ residency.
        //
        // Further complicating matters is that yield() does not work as naively expected
        // on many platforms -- yield() does not guarantee that any other ready threads
!       // will run.   As such we revert to naked_short_sleep() after some number of iterations.
!       // nakes_short_sleep() is implemented as a short unconditional sleep.
        // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
        // can actually increase the time it takes the VM thread to detect that a system-wide
        // stop-the-world safepoint has been reached.  In a pathological scenario such as that
        // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
        // In that case the mutators will be stalled waiting for the safepoint to complete and the
*** 320,332 ****
          SpinPause() ;     // MP-Polite spin
        } else
        if (steps < DeferThrSuspendLoopCount) {
          os::NakedYield() ;
        } else {
!         os::yield_all() ;
!         // Alternately, the VM thread could transiently depress its scheduling priority or
!         // transiently increase the priority of the tardy mutator(s).
        }
  
        iterations ++ ;
      }
      assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
--- 320,330 ----
          SpinPause() ;     // MP-Polite spin
        } else
        if (steps < DeferThrSuspendLoopCount) {
          os::NakedYield() ;
        } else {
!         os::naked_short_sleep(1);
        }
  
        iterations ++ ;
      }
      assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");