RFR: 8349374: [JVMCI] concurrent use of HotSpotSpeculationLog can crash

[Doug Simon]

On Tue, 4 Feb 2025 16:31:50 GMT, Tom Rodriguez <never at openjdk.org> wrote:

> This ensures that collectFailedSpeculations sees the initialization of the recently allocated failedSpeculationsAddress memory.

src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/HotSpotSpeculationLog.java line 179:

> 177:         }
> 178: 
> 179:         if (UnsafeAccess.UNSAFE.getLong(getFailedSpeculationsAddress()) != 0) {

It's still possible for `getFailedSpeculationsAddress()` to return 0 (i.e. when `managesFailedSpeculations` is `false`). So I think this should be:

diff --git a/src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/HotSpotSpeculationLog.java b/src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/HotSpotSpeculationLog.java
index fd46e281c3b..a861c00d77d 100644
--- a/src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/HotSpotSpeculationLog.java
+++ b/src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/HotSpotSpeculationLog.java
@@ -171,8 +171,9 @@ public String toString() {

     @Override
     public void collectFailedSpeculations() {
-        if (failedSpeculationsAddress != 0 && UnsafeAccess.UNSAFE.getLong(failedSpeculationsAddress) != 0) {
-            failedSpeculations = compilerToVM().getFailedSpeculations(failedSpeculationsAddress, failedSpeculations);
+        long address = getFailedSpeculationsAddress();
+        if (address != 0 && UnsafeAccess.UNSAFE.getLong(address) != 0) {
+            failedSpeculations = compilerToVM().getFailedSpeculations(address, failedSpeculations);
             assert failedSpeculations.getClass() == byte[][].class;
         }
     }

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PR Review Comment: https://git.openjdk.org/jdk/pull/23444#discussion_r1941551882