8358799: Refactor os::jvm_path() #25675

calvinccheung · 2025-06-06T16:35:15Z

The linux, bsd, and aix versions of os::jvm_path() are very similar and can be combined into one in os_posix.cpp.

Passed tiers 1 - 3 tests.
However, tests were not run on the aix platform since it is not one of the Oracle supported platforms.

Progress

Change must be properly reviewed (1 review required, with at least 1 Reviewer)
Change must not contain extraneous whitespace
Commit message must refer to an issue

Issue

JDK-8358799: Refactor os::jvm_path() (Enhancement - P4)

Reviewers

David Holmes (@dholmes-ora - Reviewer)
Johan Sjölen (@jdksjolen - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/25675/head:pull/25675
$ git checkout pull/25675

Update a local copy of the PR:
$ git checkout pull/25675
$ git pull https://git.openjdk.org/jdk.git pull/25675/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 25675

View PR using the GUI difftool:
$ git pr show -t 25675

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/25675.diff

Using Webrev

Link to Webrev Comment

bridgekeeper · 2025-06-06T16:36:11Z

👋 Welcome back ccheung! 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 · 2025-06-06T16:36:36Z

@calvinccheung 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:

8358799: Refactor os::jvm_path()

Reviewed-by: dholmes, jsjolen

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 24 new commits pushed to the master branch:

a2f99fd: 8354383: C2: enable sinking of Type nodes out of loop
0582bd2: 8357639: DigestEchoClient fails intermittently due to: java.io.IOException: Data received while in pool
3ff83ec: 8358159: Empty mode/padding in cipher transformations
... and 21 more: https://git.openjdk.org/jdk/compare/026975a1aa290613934ae421bbc56326627bad8d...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 · 2025-06-06T16:37:08Z

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

hotspot-runtime

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 · 2025-06-06T16:40:24Z

Webrevs

01: Full - Incremental (8b700565)
00: Full (8f004375)

snake66 · 2025-06-08T20:19:48Z

Not a reviewer or anything, but I'm all for this change. It will help my BSD porting efforts as well.

dholmes-ora

Good idea but I think we can go further.

Thanks

dholmes-ora · 2025-06-09T05:33:14Z

src/hotspot/os/posix/os_posix.cpp

+#ifdef AIX
+  Dl_info dlinfo;
+  int ret = dladdr(CAST_FROM_FN_PTR(void *, os::jvm_path), &dlinfo);
+  assert(ret != 0, "cannot locate libjvm");
+  char* rp = os::realpath((char *)dlinfo.dli_fname, buf, buflen);
+  assert(rp != nullptr, "error in realpath(): maybe the 'path' argument is too long?");
+#else
+  char dli_fname[MAXPATHLEN];
+  dli_fname[0] = '\0';
+  bool ret = dll_address_to_library_name(
+                                         CAST_FROM_FN_PTR(address, os::jvm_path),
+                                         dli_fname, sizeof(dli_fname), nullptr);
+  assert(ret, "cannot locate libjvm");
+  char *rp = nullptr;
+  if (ret && dli_fname[0] != '\0') {
+    rp = os::realpath(dli_fname, buf, buflen);
+  }
+  if (rp == nullptr) {
+    return;
+  }
+#endif // AIX


Given both chunks use os::realpath and otherwise only differ in error handling around realpath, I think you can reduce this further. E.g. something like

char* fname; #ifdef AIX Dl_info dlinfo; int ret = dladdr(CAST_FROM_FN_PTR(void *, os::jvm_path), &dlinfo); assert(ret != 0, "cannot locate libjvm"); fname = dlinfo.dli_fname; #else char dli_fname[MAXPATHLEN]; dli_fname[0] = '\0'; bool ret = dll_address_to_library_name( CAST_FROM_FN_PTR(address, os::jvm_path), dli_fname, sizeof(dli_fname), nullptr); assert(ret, "cannot locate libjvm"); fname = dli_fname; #endif char* rp = nullprtr; ...

I would also be asking the AIX folk if there is a reason they use dladdr directly instead of os::dll_address_to_library_name?

AIX is very different in this regard. There is a hand-crafted partial implementation of dladdr in src/hotspot/os/aix/porting_aix.cpp. I'm not sure this is the reason, just pointing out that this is a typical weakness of AIX where it differs from other unix systems wrt to dladdr.

I've updated the PR based on David's comment and have left the dladdr alone for now.

jdksjolen · 2025-06-09T09:41:10Z

src/hotspot/os/posix/os_posix.cpp

+  Dl_info dlinfo;
+  int ret = dladdr(CAST_FROM_FN_PTR(void *, os::jvm_path), &dlinfo);
+  assert(ret != 0, "cannot locate libjvm");
+  char* rp = os::realpath((char *)dlinfo.dli_fname, buf, buflen);
+  assert(rp != nullptr, "error in realpath(): maybe the 'path' argument is too long?");


Pre-existing: We should return if ret == 0 and rp == nullptr, not continue as if it didn't fail.

I've added the check for ret.

sendaoYan · 2025-06-10T00:39:06Z

src/hotspot/os/posix/os_posix.cpp

+  if (buflen < MAXPATHLEN) {
+    assert(false, "must use a large-enough buffer");
+    buf[0] = '\0';
+    return;


Do we need release the memory of buf before return, such like

free(buf);

No, because the caller of the function still references buf after the function returns, e.g. in os::init_system_properties_values().

More specifically, buf is owned by the caller and we have no idea what it is so we have no business "releasing" it.

dholmes-ora

I'd still like some input from AIX folk on whether we can do better here, but in lieu of that this seems good enough to me.

Thanks

jdksjolen

I'm also OK with this.

calvinccheung · 2025-06-10T16:19:35Z

Thanks @dholmes-ora @jdksjolen for the review.

/integrate

openjdk · 2025-06-10T16:20:36Z

Going to push as commit 500a3a2.
Since your change was applied there have been 24 commits pushed to the master branch:

a2f99fd: 8354383: C2: enable sinking of Type nodes out of loop
0582bd2: 8357639: DigestEchoClient fails intermittently due to: java.io.IOException: Data received while in pool
3ff83ec: 8358159: Empty mode/padding in cipher transformations
... and 21 more: https://git.openjdk.org/jdk/compare/026975a1aa290613934ae421bbc56326627bad8d...master

Your commit was automatically rebased without conflicts.

openjdk · 2025-06-10T16:20:45Z

@calvinccheung Pushed as commit 500a3a2.

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

8358799: Refactor os::jvm_path()

8f00437

calvinccheung marked this pull request as ready for review June 6, 2025 16:35

openjdk bot added the rfr Pull request is ready for review label Jun 6, 2025

openjdk bot added the hotspot-runtime [email protected] label Jun 6, 2025

dholmes-ora suggested changes Jun 9, 2025

View reviewed changes

jdksjolen reviewed Jun 9, 2025

View reviewed changes

calvinccheung added 2 commits June 9, 2025 16:03

Merge branch 'master' into 8358799-refactor-jvm-path

a8b0c33

review comments from @dholmes-ora and @jdksjolen

8b70056

sendaoYan reviewed Jun 10, 2025

View reviewed changes

dholmes-ora approved these changes Jun 10, 2025

View reviewed changes

openjdk bot added the ready Pull request is ready to be integrated label Jun 10, 2025

jdksjolen approved these changes Jun 10, 2025

View reviewed changes

openjdk bot added the integrated Pull request has been integrated label Jun 10, 2025

openjdk bot closed this Jun 10, 2025

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Jun 10, 2025

calvinccheung deleted the 8358799-refactor-jvm-path branch June 10, 2025 16:24

8358799: Refactor os::jvm_path() #25675

8358799: Refactor os::jvm_path() #25675

Uh oh!

Conversation

calvinccheung commented Jun 6, 2025 • edited by openjdk bot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Progress

Issue

Reviewers

Reviewing

Uh oh!

bridgekeeper bot commented Jun 6, 2025

Uh oh!

openjdk bot commented Jun 6, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

openjdk bot commented Jun 6, 2025

Uh oh!

mlbridge bot commented Jun 6, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Webrevs

Uh oh!

snake66 commented Jun 8, 2025

Uh oh!

dholmes-ora left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

dholmes-ora left a comment

Choose a reason for hiding this comment

Uh oh!

jdksjolen left a comment

Choose a reason for hiding this comment

Uh oh!

calvinccheung commented Jun 10, 2025

Uh oh!

openjdk bot commented Jun 10, 2025

Uh oh!

openjdk bot commented Jun 10, 2025

Uh oh!

Uh oh!

calvinccheung commented Jun 6, 2025 •

edited by openjdk bot

Loading

openjdk bot commented Jun 6, 2025 •

edited

Loading

mlbridge bot commented Jun 6, 2025 •

edited

Loading