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                                     ObjectMonitor              T-deflate
    T-enter                          +-----------------------+  --------------------------------------------
    -------------------------------  | owner=DEFLATER_MARKER |  deflate_monitor_using_JT() {
    owner contended                  | contentions=-max_jint |    cmpxchg(DEFLATER_MARKER, &owner, NULL)
    atomic inc contentions           +-----------------------+    :
    if (contentions <= 0 && owner                                                                    prev = cmpxchg(-max_jint, &contentions, 0)
        owner == DEFLATER_MARKER) {                                                          if (prev == 0 &&
      restore obj header                   header                                                  owner == DEFLATER_MARKER) {
      retry enter                                                   restore obj header
    }                                                               finish the deflation
                                                                  }

• • This diagram starts after "Racing Threads".
  • T-enter and T-deflate both observe owner == DEFLATER_MARKER and a negative contentions field.
  • T-enter has lost the race, it restores the obj header and it retries.
  • T-deflate restores the obj header and it finishes deflation of the ObjectMonitor.

T-enter Wins

                                     ObjectMonitor              T-deflate
    T-enter                          +-----------------------+  --------------------------------------------
    ---------------------- ---------  | owner=DEFLATER_MARKER |  deflate_monitor_using_JT() {
    owner contended                  | contentions=1         |    cmpxchg(DEFLATER_MARKER, &owner, NULL)
    atomic inc contentions           +-----------------------+    :
    if (contentions ><= 0)                               &&                                       prev = cmpxchg(-max_jint, &contentions, 0)
      do  contended                        owner == DEFLATER_MARKER) {              if (prev                       if (prev == 0 &&
         } else {                                enter work                                                         owner == DEFLATER_MARKER) {
      do  contended                                                 } else {
        enter work                                                  cmpxchg(NULL, &owner, DEFLATER_MARKER)

...

                                                ObjectMonitor                T-deflate
    T-enter                                     +-------------------------+  ------------------------------------------
    ------------------------------------------  | owner=DEFLATER_MARKER   |  deflate_monitor_using_JT() {
    owner contended                             | contentions=1           |    cmpxchg(DEFLATER_MARKER, &owner, NULL)
    atomic inc contentions                      +-------------------------+ 1> :
 1> if (contentions ><= 0) &&                                    ||              2> : <thread_stalls>
      EnterI()   owner == DEFLATER_MARKER) {                         \/                                               :
    } else {            \/                 :
        cmpxchg(Self, &owner, DEFLATER_MARKER)  +-------------------------+    :
      atomicEnterI() dec contentions                    | owner=Self/T-enter      |    :
 2> }| owner=Self/T-enter      |    :
        cmpxchg(Self, &owner,                        DEFLATER_MARKER)  | contentions=0           |    : <thread_resumes>
    // finished withatomic enterdec contentions                     +-------------------------+    prev = cmpxchg(-max_jint, &contentions, 0)
 3> : <does app work>2> }                                                       ||                 if (prev == 0 &&
    exit() monitor        // finished with enter                                  \/                     owner == DEFLATER_MARKER) {
 3> : <does app  owner =work> NULL                              +-------------------------+    } else {
              exit() monitor                                  | owner=Self/T-enter|NULL |      cmpxchg(NULL, &owner, DEFLATER_MARKER)
      owner            = NULL                              | contentions=0           |      atomic add max_jint to contentions
                                                +-------------------------+   3> bailout on deflation
                                                                               }

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