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8213436: Obsolete UseMembar

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Reviewed-by: kvn, dholmes, mdoerr, adinn
This commit is contained in:
Mikael Vidstedt 2018-11-08 11:45:13 -08:00
parent 38a1e5ffbc
commit f69921f2fc
57 changed files with 43 additions and 655 deletions
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16
src/hotspot/share/runtime/safepoint.cpp
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@ -213,16 +213,7 @@ void SafepointSynchronize::begin() {
// writes and reads of both the safepoint state and the Java
// threads state is critical. In order to guarantee that the
// memory writes are serialized with respect to each other,
// the VM thread issues a memory barrier instruction
// (on MP systems). In order to avoid the overhead of issuing
// a memory barrier for each Java thread making native calls, each Java
// thread performs a write to a single memory page after changing
// the thread state. The VM thread performs a sequence of
// mprotect OS calls which forces all previous writes from all
// Java threads to be serialized. This is done in the
// os::serialize_thread_states() call. This has proven to be
// much more efficient than executing a membar instruction
// on every call to native code.
// the VM thread issues a memory barrier instruction.
// 3. Running compiled Code
// Compiled code reads a global (Safepoint Polling) page that
// is set to fault if we are trying to get to a safepoint.
@ -251,11 +242,6 @@ void SafepointSynchronize::begin() {
}
OrderAccess::fence(); // storestore|storeload, global state -> local state
// Flush all thread states to memory
if (!UseMembar) {
os::serialize_thread_states();
}
if (SafepointMechanism::uses_global_page_poll()) {
// Make interpreter safepoint aware
Interpreter::notice_safepoints();