Page History

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• • This diagram starts after "Racing Threads".
  • The "1>" markers are showing where each thread is at for the ObjectMonitor box:
    
    • T-enter and T-deflate both observe a contentions field > 0.
  • T-enter has won the race and it continues with the contended enter protocol.
  • T-deflate detects that it has lost the race (prev != 0) and bails out on deflating the ObjectMonitor:
    
    • Before bailing out T-deflate tries to restore the owner field to NULL if it is still DEFLATER_MARKER.
  • The "2>" markers are showing where each thread is at for that ObjectMonitor box.
  • Note: The owner == DEFLATER_MARKER and contentions < 0 values that are set by T-deflate (stage one of async deflation) remain in place until after T-deflate does a handshake operation with all JavaThreads. This handshake forces T-enter to make forward progress and see that the ObjectMonitor is being async deflated before T-enter checks in for the handshake.

T-enter Wins By Cancellation Via DEFLATER_MARKER Swap

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