8346082: Output JVMTI agent information in hserr files by MBaesken · Pull Request #22706 · openjdk/jdk

MBaesken · 2024-12-12T09:42:36Z

We should output more information about the JVMTI agents in the hserr file.

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Issue

JDK-8346082: Output JVMTI agent information in hserr files (Enhancement - P4)

Reviewers

David Holmes (@dholmes-ora - Reviewer) Review applies to fa422ce3
Martin Doerr (@TheRealMDoerr - Reviewer)
Thomas Stuefe (@tstuefe - Reviewer) Review applies to fa960c86

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bridgekeeper · 2024-12-12T09:43:23Z

👋 Welcome back mbaesken! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2024-12-12T09:43:31Z

@MBaesken This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8346082: Output JVMTI agent information in hserr files

Reviewed-by: mdoerr, dholmes, stuefe

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 39 new commits pushed to the master branch:

45a3297: 8346248: serviceability/dcmd/vm/{SystemMapTest.java,SystemMapTest.java} failing on macos-aarch64
dbffe33: 8345263: Make sure that lint categories are used correctly when logging lint warnings
32c8195: 8345801: C2: Clean up include statements to speed up compilation when touching type.hpp
9286018: 8345322: RISC-V: Add concurrent gtests for cmpxchg variants
4fc43b0: 8345770: javadoc: API documentation builds are not always reproducible
ee1c5ad: 8345975: Update SAP SE copyright year to 2024 where it was missed
3518b4b: 8344171: Clone and initialize Assertion Predicates in order instead of in reverse-order
c88e081: 8346160: Fix -Wzero-as-null-pointer-constant warnings from explicit casts
ab1dbd4: 8346202: Correct typo in SQLPermission
6b022bb: 8344453: Test jdk/jfr/event/oldobject/TestSanityDefault.java timed out
... and 29 more: https://git.openjdk.org/jdk/compare/3f2556b86079fbdba848b1ac16b62a376386999b...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

openjdk · 2024-12-12T09:44:26Z

@MBaesken The following label will be automatically applied to this pull request:

hotspot

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

mlbridge · 2024-12-12T09:47:09Z

Webrevs

src/hotspot/share/runtime/os.cpp

src/hotspot/share/utilities/vmError.cpp

dholmes-ora · 2024-12-12T20:39:25Z

/label add sereviceability

dholmes-ora · 2024-12-12T20:39:39Z

/label add serviceability

openjdk · 2024-12-12T20:40:27Z

@dholmes-ora
The label sereviceability is not a valid label.
These labels are valid:

graal
serviceability
hotspot
hotspot-compiler
ide-support
kulla
i18n
shenandoah
jdk
javadoc
security
hotspot-runtime
jmx
build
nio
client
core-libs
compiler
net
hotspot-gc
hotspot-jfr

openjdk · 2024-12-12T20:40:34Z

@dholmes-ora
The serviceability label was successfully added.

dholmes-ora

Seems okay. Someone from serviceability should give their opinion on the content.

larry-cable · 2024-12-12T21:43:12Z

I do not understand the use case that this additional information solves for, nor does the bug provide any further enlightenment, I think this ER requires more rationale to motivate its inclusion.

src/hotspot/share/runtime/os.cpp

MBaesken · 2024-12-13T08:35:26Z

I do not understand the use case that this additional information solves for, nor does the bug provide any further enlightenment, I think this ER requires more rationale to motivate its inclusion.

Currently the info about the JVMTI agents in the hserr/hsinfo is not good. You might see them in the so/dll list and maybe command-line output but this is far from ideal. A little separate section gives more clarity.
Bad JVMTI agents (and even good ones) can influence what is going on at runtime so that info should be present.

TheRealMDoerr

Nice enhancement! Could you add an example output to the description, please?

src/hotspot/share/runtime/os.cpp

tstuefe

Looks fine, two bikeshedding nits.

I approve now, up to you if you take my suggestions.

tstuefe · 2024-12-13T15:34:57Z

src/hotspot/share/runtime/os.cpp

+      const char* instrumentinfo = agent->is_instrument_lib() ? "instrumentlib" : "";
+      const char* loadinfo = agent->is_loaded() ? "loaded" : "not loaded";
+      const char* initinfo = agent->is_initialized() ? "initialized" : "not initialized";


I would just print these as flags, its clearer and simpler to print. E.g.

"myagent path: mylib.so dynamic:1 loaded:1 instrument_lib:0 initialized:1 xxx options xxx"

tstuefe · 2024-12-13T15:37:17Z

src/hotspot/share/runtime/os.cpp

+  while (it.has_next()) {
+    const JvmtiAgent* agent = it.next();
+    if (agent != nullptr) {
+      if (first_agent) st->print_cr("JVMTI agents:");


if no agents are loaded, I would print "JVMTI agents: none" unconditionally. Makes it more obvious than just a missing entry; that could be also an error.

MBaesken · 2024-12-13T15:51:37Z

Nice enhancement! Could you add an example output to the description, please?

Currently it looks like this

JVMTI agents:
asyncProfiler path:none, loaded, initialized   options:start,flat=10000,interval=50us,traces=1,event=wall,loglevel=none

(example is from a JVM started with async-profiler : images/jdk/bin/java -agentlib:asyncProfiler=start,flat=10000,interval=50us,traces=1,event=wall,loglevel=none .... )

MBaesken · 2024-12-13T15:57:31Z

if no agents are loaded, I would print "JVMTI agents: none" unconditionally. Makes it more obvious than just a missing entry; >that could be also an error.

Maybe after the while loop something like this ?

  bool first_agent = true;
  while (it.has_next()) {
      ...
  }
  **if (first_agent) st->print_cr("JVMTI agents: none");**

alexmenkov · 2024-12-13T21:19:43Z

if no agents are loaded, I would print "JVMTI agents: none" unconditionally. Makes it more obvious than just a missing entry; >that could be also an error.

Maybe after the while loop something like this ?
  bool first_agent = true;
  while (it.has_next()) {
      ...
  }
  **if (first_agent) st->print_cr("JVMTI agents: none");**

You can do it before the loop:

if (it.has_next()) {
  st->print_cr("JVMTI agents:");
} else {
  st->print_cr("JVMTI agents: none");
}

and get rid of first_agent variable

MBaesken · 2024-12-16T08:13:50Z

When printing 'JVMTI agents: none' , should I maybe better iterate JvmtiAgentList::all() to get the xrun agents as well and be sure that there are really none ?
Unfortunately JvmtiAgentList::all() is private , any objections making it public ? Otherwise we probably need to call 2 iterations (agents() and xrun_agents()).

TheRealMDoerr

LGTM.

MBaesken · 2024-12-16T14:32:54Z

Hi Martin, David, Thomas, thanks for the reviews !

(should we consider adding the JVMTI agent output to jcmd too as a separate command/option? (but not in this change) )

mlbridge · 2024-12-16T16:28:29Z

Mailing list message from Laurence Cable on serviceability-dev:

again what's the use case?

On 12/16/24 6:35 AM, Matthias Baesken wrote:

TheRealMDoerr · 2024-12-16T16:43:23Z

again what's the use case?

Assume a customer uses a tool like the async profiler and causes a JVM crash by doing that. A supporter looks at the hs_err file and wonders about what might have happened. Such a hint would be very helpful.

mlbridge · 2024-12-16T18:11:29Z

Mailing list message from Laurence Cable on serviceability-dev:

On 12/16/24 8:45 AM, Martin Doerr wrote:

On Mon, 16 Dec 2024 16:28:29 GMT, Laurence Cable <larry.cable at oracle.com> wrote:

again what's the use case?
Assume a customer uses a tool like the async profiler and causes a JVM crash by doing that. A supporter looks at the hs_err file and wonders about what might have happened. Such a hint would be very helpful.

I was referring to the suggestion that there should be a jcmd to emit
agent info ... I dont see that as useful

MBaesken · 2024-12-16T18:22:19Z

jcmd to emit agent info

Okay, then let's avoid adding it to jcmd; for hserr/hsinfo adding the info is more important.

My idea was that currently we can do 'data dump' and 'load agents' with jcmd

JVMTI.agent_load
JVMTI.data_dump

So for completeness, when you offer loading agents, it might be useful to be able to show the current agents with the same tool jcmd. But on the other hand you are probably correct that this new option might not be used a lot so it is maybe not worth the effort.

MBaesken · 2024-12-16T18:22:59Z

/integrate

openjdk · 2024-12-16T18:24:16Z

Going to push as commit c75b1d4.
Since your change was applied there have been 48 commits pushed to the master branch:

51662c2: 8346232: Remove leftovers of the jar --normalize feature
d335941: 8345678: compute_modifiers should not be in create_mirror
57adf64: 8346261: Cleanup in JDP tests
23708d0: 8346257: Problemlist jdp tests for macosx-aarch64
f8974ba: 8345838: Remove the appcds/javaldr/AnonVmClassesDuringDump.java test
e7d21fc: 8346285: Update jarsigner compatibility test for change in default digest algorithm
cb92595: 8336356: [s390x] preserve Vector Register before using for string compress / expand
d737978: 8343477: Remove unnecessary @SuppressWarnings annotations (compiler)
8133eb2: 8346150: Jib dependency on autoconf missing for 'docs' profile
45a3297: 8346248: serviceability/dcmd/vm/{SystemMapTest.java,SystemMapTest.java} failing on macos-aarch64
... and 38 more: https://git.openjdk.org/jdk/compare/3f2556b86079fbdba848b1ac16b62a376386999b...master

Your commit was automatically rebased without conflicts.

openjdk · 2024-12-16T18:24:22Z

@MBaesken Pushed as commit c75b1d4.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

tstuefe · 2024-12-16T18:39:01Z

jcmd to emit agent info

Okay, then let's avoid adding it to jcmd; for hserr/hsinfo adding the info is more important.

My idea was that currently we can do 'data dump' and 'load agents' with jcmd
JVMTI.agent_load
JVMTI.data_dump
So for completeness, when you offer loading agents, it might be useful to be able to show the current agents with the same tool jcmd. But on the other hand you are probably correct that this new option might not be used a lot so it is maybe not worth the effort.

Since we already have VM.info jcmd, which after your patch already shows jvmti info, a separate command would be redundant, no?

JDK-8346082

b6be8ec

openjdk bot changed the title ~~JDK-8346082: Output JVMTI agent information is hserr files~~ 8346082: Output JVMTI agent information is hserr files Dec 12, 2024

openjdk bot added the rfr Pull request is ready for review label Dec 12, 2024

openjdk bot added the hotspot hotspot-dev@openjdk.org label Dec 12, 2024

dholmes-ora reviewed Dec 12, 2024

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MBaesken added 2 commits December 12, 2024 13:33

remove unneeded code

738dd8f

infos -> info

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MBaesken changed the title ~~8346082: Output JVMTI agent information is hserr files~~ 8346082: Output JVMTI agent information in hserr files Dec 13, 2024

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simplify coding

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Adjust output a bit, print xrun agents too

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adjust spaces in output

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