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8152358: code and comment cleanups found during the hunt for 8077392

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Reviewed-by: gthornbr, kvn, cvarming
This commit is contained in:
Daniel D. Daugherty 2016-04-04 14:49:19 -07:00
parent 66570c722b
commit 2e87e3178c
8 changed files with 71 additions and 43 deletions
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5
hotspot/src/share/vm/runtime/objectMonitor.cpp
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@ -850,7 +850,7 @@ void ObjectMonitor::UnlinkAfterAcquire(Thread *Self, ObjectWaiter *SelfNode) {
// ~~~~~~~~
// ::exit() uses a canonical 1-1 idiom with a MEMBAR although some of
// the fast-path operators have been optimized so the common ::exit()
// operation is 1-0. See i486.ad fast_unlock(), for instance.
// operation is 1-0, e.g., see macroAssembler_x86.cpp: fast_unlock().
// The code emitted by fast_unlock() elides the usual MEMBAR. This
// greatly improves latency -- MEMBAR and CAS having considerable local
// latency on modern processors -- but at the cost of "stranding". Absent the
@ -863,7 +863,7 @@ void ObjectMonitor::UnlinkAfterAcquire(Thread *Self, ObjectWaiter *SelfNode) {
//
// The CAS() in enter provides for safety and exclusion, while the CAS or
// MEMBAR in exit provides for progress and avoids stranding. 1-0 locking
// eliminates the CAS/MEMBAR from the exist path, but it admits stranding.
// eliminates the CAS/MEMBAR from the exit path, but it admits stranding.
// We detect and recover from stranding with timers.
//
// If a thread transiently strands it'll park until (a) another
@ -936,7 +936,6 @@ void ObjectMonitor::exit(bool not_suspended, TRAPS) {
for (;;) {
assert(THREAD == _owner, "invariant");
if (Knob_ExitPolicy == 0) {
// release semantics: prior loads and stores from within the critical section
// must not float (reorder) past the following store that drops the lock.