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8349374: [JVMCI] concurrent use of HotSpotSpeculationLog can crash #23444

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8349374: [JVMCI] concurrent use of HotSpotSpeculationLog can crash #23444

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8349374: [JVMCI] concurrent use of HotSpotSpeculationLog can crash
tkrodriguez Feb 4, 2025
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improve javadoc
tkrodriguez Feb 4, 2025
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tkrodriguez Feb 4, 2025
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19 changes: 14 additions & 5 deletions src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/HotSpotSpeculationLog.java
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Original file line number Diff line number Diff line change
Expand Up @@ -77,16 +77,17 @@ public HotSpotSpeculationLog(long failedSpeculationsAddress) {
}

/**
* Gets the address of the pointer to the native failed speculations list.
* Gets the address of the pointer to the native failed speculations list. This always returns a non-zero address.
*
* @see #managesFailedSpeculations()
*/
public long getFailedSpeculationsAddress() {
if (managesFailedSpeculations) {
synchronized (this) {
if (failedSpeculationsAddress == 0L) {
failedSpeculationsAddress = UnsafeAccess.UNSAFE.allocateMemory(HotSpotJVMCIRuntime.getHostWordKind().getByteCount());
UnsafeAccess.UNSAFE.putAddress(failedSpeculationsAddress, 0L);
long address = UnsafeAccess.UNSAFE.allocateMemory(HotSpotJVMCIRuntime.getHostWordKind().getByteCount());
UnsafeAccess.UNSAFE.putAddress(address, 0L);
failedSpeculationsAddress = address;
LogCleaner c = new LogCleaner(this, failedSpeculationsAddress);
assert c.address == failedSpeculationsAddress;
}
Expand Down Expand Up @@ -171,8 +172,16 @@ public String toString() {

@Override
public void collectFailedSpeculations() {
if (failedSpeculationsAddress != 0 && UnsafeAccess.UNSAFE.getLong(failedSpeculationsAddress) != 0) {
failedSpeculations = compilerToVM().getFailedSpeculations(failedSpeculationsAddress, failedSpeculations);
if (failedSpeculationsAddress == 0) {
// If no memory has been allocated then don't force its creation
return;
}

// Go through getFailedSpeculationsAddress() to ensure that any concurrent
// initialization of failedSpeculationsAddress is seen by this thread.
long address = getFailedSpeculationsAddress();
if (UnsafeAccess.UNSAFE.getLong(address) != 0) {
failedSpeculations = compilerToVM().getFailedSpeculations(address, failedSpeculations);
assert failedSpeculations.getClass() == byte[][].class;
}
}
Expand Down