JDK-8067331 : Zero: Atomic::xchg and Atomic::xchg_ptr need full memory barrier
- Type: Bug
- Component: hotspot
- Sub-Component: runtime
- Affected Version: 9
- Priority: P4
- Status: Resolved
- Resolution: Fixed
- OS: generic
- CPU: generic
- Submitted: 2014-12-12
- Updated: 2015-09-29
- Resolved: 2015-01-08
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| JDK 8 | JDK 9 |
|---|---|
8u60Fixed  |
9 b48Fixed |
Description
Some code in hotspot depends on Atomic::xchg to be a full memory barrier. Example:
void Parker::park(bool isAbsolute, jlong time) {
// Ideally we'd do something useful while spinning, such
// as calling unpackTime().
// Optional fast-path check:
// Return immediately if a permit is available.
// We depend on Atomic::xchg() having full barrier semantics
// since we are doing a lock-free update to _counter.
if (Atomic::xchg(0, &_counter) > 0) return;
However, the Zero implementation is not implemented as a full memory barrier.
Comments
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