RFR: 8297286: runtime/vthread tests crashing after JDK-8296324 [v5]

[Chris Plummer]

On Thu, 23 Mar 2023 05:54:29 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

>> The fix is to enable virtual threads support for late binding JVMTI agents.
>> The fix includes:
>> - New function `JvmtiEnvBase::enable_virtual_threads_notify_jvmti()` which does enabling JVMTI VTMS transition notifications in case of agent loaded into running VM. This function executes a VM operation counting VTMS transition bits in all `JavaThread`'s to correctly set the static counter `_VTMS_transition_count` needed for VTMS transition protocol.
>> - New function `JvmtiEnvBase::disable_virtual_threads_notify_jvmti()` which is needed for testing. It is used by the `WhiteBox` API.
>> - New WhiteBox function `WB_SetVirtualThreadsNotifyJvmtiMode(JNIEnv* env, jobject wb, jboolean enable)` needed for testing of this update.
>> - New regression test: `serviceability/jvmti/vthread/ToggleNotifyJvmtiTest`
>> 
>> Testing:
>> - New test: `serviceability/jvmti/vthread/ToggleNotifyJvmtiTest`
>> - The originally failed tests are expected to pass now:
>>   `runtime/vthread/RedefineClass.java`
>>   `runtime/vthread/TestObjectAllocationSampleEvent.java` 
>> - In progress: Run the tiers 1-6 to make sure there are no regression.
>
> Serguei Spitsyn has updated the pull request incrementally with one additional commit since the last revision:
> 
>   address review comment: remove unneeded function

src/hotspot/share/prims/jvmtiThreadState.hpp line 101:

> 99:   static void set_VTMS_notify_jvmti_events(bool val) { _VTMS_notify_jvmti_events = val; }
> 100: 
> 101:   static void set_VTMS_transition_count(bool val)    { _VTMS_transition_count = val; }

Why set the count if it is never going to be used?

test/hotspot/jtreg/serviceability/jvmti/vthread/ToggleNotifyJvmtiTest/ToggleNotifyJvmtiTest.java line 38:

> 36:  */
> 37: 
> 38: //import compiler.whitebox.CompilerWhiteBoxTest;

Remove

test/hotspot/jtreg/serviceability/jvmti/vthread/ToggleNotifyJvmtiTest/ToggleNotifyJvmtiTest.java line 68:

> 66:             if (n <= 0) {
> 67:                 n = 1000;
> 68:                 ToggleNotifyJvmtiTest.sleep(1);

It looks like you do this short sleep 1 out of every 1,000,000 iterations. Can you explain why?

test/hotspot/jtreg/serviceability/jvmti/vthread/ToggleNotifyJvmtiTest/ToggleNotifyJvmtiTest.java line 72:

> 70:             if (i > n) {
> 71:                 i = 0;
> 72:                 n = n - 1;

n--

test/hotspot/jtreg/serviceability/jvmti/vthread/ToggleNotifyJvmtiTest/ToggleNotifyJvmtiTest.java line 74:

> 72:                 n = n - 1;
> 73:             }
> 74:             i = i + 1;

i++

test/hotspot/jtreg/serviceability/jvmti/vthread/ToggleNotifyJvmtiTest/ToggleNotifyJvmtiTest.java line 148:

> 146: 
> 147:     static private void setVirtualThreadsNotifyJvmtiMode(int iter, boolean enable) {
> 148:         sleep(5);

Why is this needed?

test/hotspot/jtreg/serviceability/jvmti/vthread/ToggleNotifyJvmtiTest/ToggleNotifyJvmtiTest.java line 157:

> 155: 
> 156:         if (args.length > 0 && args[0].equals("attach")) { // agent loaded into running VM case
> 157:             String arg = args.length == 2 ? args[1] : "";

I don't see any args being passed in other than "attach"? What might `arg` be set to?

test/hotspot/jtreg/serviceability/jvmti/vthread/ToggleNotifyJvmtiTest/ToggleNotifyJvmtiTest.java line 161:

> 159:             vm.loadAgentLibrary(AGENT_LIB, arg);
> 160:         } else {
> 161:             System.loadLibrary(AGENT_LIB);

Why is this needed? Isn't the library already loaded due to it being specified by `-agentlib`?

test/hotspot/jtreg/serviceability/jvmti/vthread/ToggleNotifyJvmtiTest/ToggleNotifyJvmtiTest.java line 171:

> 169:         sleep(20);
> 170: 
> 171:         for (int iter = 0; VirtualThreadStartedCount() < VTHREADS_CNT; iter++) {

The test seems to exit once all the threads are started. I would think you would want it to run for a while after all the threads are started.

test/hotspot/jtreg/serviceability/jvmti/vthread/ToggleNotifyJvmtiTest/libToggleNotifyJvmtiTest.cpp line 32:

> 30: 
> 31: static jvmtiEnv *jvmti;
> 32: static int vthread_started_cnt = 0;

Needs to be volatile?

test/hotspot/jtreg/serviceability/jvmti/vthread/ToggleNotifyJvmtiTest/libToggleNotifyJvmtiTest.cpp line 34:

> 32: static int vthread_started_cnt = 0;
> 33: static jrawMonitorID agent_lock = NULL;
> 34: static bool can_support_vt_enabled = false;

This variable doesn't seem to be needed. You set it `true` later on, but never reference it.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/13133#discussion_r1146578471
PR Review Comment: https://git.openjdk.org/jdk/pull/13133#discussion_r1146594032
PR Review Comment: https://git.openjdk.org/jdk/pull/13133#discussion_r1146608558
PR Review Comment: https://git.openjdk.org/jdk/pull/13133#discussion_r1146598256
PR Review Comment: https://git.openjdk.org/jdk/pull/13133#discussion_r1146598429
PR Review Comment: https://git.openjdk.org/jdk/pull/13133#discussion_r1146625993
PR Review Comment: https://git.openjdk.org/jdk/pull/13133#discussion_r1146620881
PR Review Comment: https://git.openjdk.org/jdk/pull/13133#discussion_r1146624531
PR Review Comment: https://git.openjdk.org/jdk/pull/13133#discussion_r1146629460
PR Review Comment: https://git.openjdk.org/jdk/pull/13133#discussion_r1146630461
PR Review Comment: https://git.openjdk.org/jdk/pull/13133#discussion_r1146633746