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8238174: migrate ObjectMonitor::_owner field away from C++ volatile semantics

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Reviewed-by: dholmes, mdoerr
This commit is contained in:
Daniel D. Daugherty 2020-11-18 16:48:17 +00:00
parent 50a2c22ff7
commit 1707d5ca3c
4 changed files with 48 additions and 42 deletions
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11
src/hotspot/share/runtime/objectMonitor.hpp
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@ -147,13 +147,13 @@ class ObjectMonitor : public CHeapObj<mtInternal> {
sizeof(WeakHandle));
// Used by async deflation as a marker in the _owner field:
#define DEFLATER_MARKER reinterpret_cast<void*>(-1)
void* volatile _owner; // pointer to owning thread OR BasicLock
void* _owner; // pointer to owning thread OR BasicLock
volatile jlong _previous_owner_tid; // thread id of the previous owner of the monitor
// Separate _owner and _next_om on different cache lines since
// both can have busy multi-threaded access. _previous_owner_tid is only
// changed by ObjectMonitor::exit() so it is a good choice to share the
// cache line with _owner.
DEFINE_PAD_MINUS_SIZE(1, OM_CACHE_LINE_SIZE, sizeof(void* volatile) +
DEFINE_PAD_MINUS_SIZE(1, OM_CACHE_LINE_SIZE, sizeof(void*) +
sizeof(volatile jlong));
ObjectMonitor* _next_om; // Next ObjectMonitor* linkage
volatile intx _recursions; // recursion count, 0 for first entry
@ -242,8 +242,8 @@ class ObjectMonitor : public CHeapObj<mtInternal> {
if (contentions() > 0) {
ret_code |= contentions();
}
if (_owner != DEFLATER_MARKER) {
ret_code |= intptr_t(_owner);
if (!owner_is_DEFLATER_MARKER()) {
ret_code |= intptr_t(owner_raw());
}
return ret_code;
}
@ -252,8 +252,9 @@ class ObjectMonitor : public CHeapObj<mtInternal> {
intptr_t is_entered(Thread* current) const;
void* owner() const; // Returns NULL if DEFLATER_MARKER is observed.
void* owner_raw() const;
// Returns true if owner field == DEFLATER_MARKER and false otherwise.
bool owner_is_DEFLATER_MARKER();
bool owner_is_DEFLATER_MARKER() const;
// Returns true if 'this' is being async deflated and false otherwise.
bool is_being_async_deflated();
// Clear _owner field; current value must match old_value.