JDK-6888847 : TaskQueue needs release_store() for correctness on RMO machines
  • Type: Bug
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: hs17
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • OS: generic
  • CPU: generic
  • Submitted: 2009-10-06
  • Updated: 2013-01-26
  • Resolved: 2009-11-11
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JDK 6 JDK 7 Other
6u21Fixed 7Fixed hs17Fixed
Related Reports
Relates :  
JDK-8006971 - More missing barriers in taskqueues for RMO architectures
Relates :  
JDK-6379795 - memory fences missing in concurrent mark sweep GC code
Description
Even though the task queues work correctly on TSO machines, it turns out that they are incorrect when ran on non-TSO machines, as they are missing two release_stores.
Comments
EVALUATION http://hg.openjdk.java.net/jdk7/hotspot-gc/hotspot/rev/2c03ce058f55
08-10-2009
SUGGESTED FIX Thanks to Bob Vandette for the fix.
06-10-2009
SUGGESTED FIX @@ -205,11 +205,11 @@ bool GenericTaskQueue<E>::push_slow(E t, uint dirty_n_elems) { if (dirty_n_elems == N - 1) { // Actually means 0, so do the push. uint localBot = _bottom; _elems[localBot] = t; - _bottom = increment_index(localBot); + OrderAccess::release_store(&_bottom, increment_index(localBot)); return true; } return false; } @@ -483,11 +483,11 @@ idx_t top = _age.top(); uint dirty_n_elems = dirty_size(localBot, top); assert((dirty_n_elems >= 0) && (dirty_n_elems < N), "n_elems out of range."); if (dirty_n_elems < max_elems()) { _elems[localBot] = t; - _bottom = increment_index(localBot); + OrderAccess::release_store(&_bottom, increment_index(localBot)); return true; } else { return push_slow(t, dirty_n_elems); } #endif
06-10-2009
EVALUATION Add release_stores where appropriate.
06-10-2009