8351322: Parameterize link option for pthreads #23930

snake66 · 2025-03-06T10:39:27Z

Replace hardcoded instances of -lpthread with $(LIBPTHREAD), so that it's possible to parameterize this for platforms that use different flags for enabling posix threads.

This work is a continuation of the work done by Greg Lewis in 1, but generalized for the full JDK, and set at the configure stage.

Sponsored by: The FreeBSD Foundation
Co-authored-by: Greg Lewis [email protected]

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JDK-8351322: Parameterize link option for pthreads (Enhancement - P4)

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David Holmes (@dholmes-ora - Reviewer)

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$ git fetch https://git.openjdk.org/jdk.git pull/23930/head:pull/23930
$ git checkout pull/23930

Update a local copy of the PR:
$ git checkout pull/23930
$ git pull https://git.openjdk.org/jdk.git pull/23930/head

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$ git pr checkout 23930

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https://git.openjdk.org/jdk/pull/23930.diff

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Replace hardcoded instances of `-lpthread` with `$(LIBPTHREAD)`, so that it's possible to parameterize this for platforms that use different flags for enabling posix threads. This work is a continuation of the work done by Greg Lewis in [1], but generalized for the full JDK, and set at the configure stage. Sponsored by: The FreeBSD Foundation Co-authored-by: Greg Lewis <[email protected]> [1]: battleblow/jdk23u@dbd90aa

bridgekeeper · 2025-03-06T10:40:21Z

👋 Welcome back snake66! 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 · 2025-03-06T10:41:35Z

@snake66 This change is no longer ready for integration - check the PR body for details.

openjdk · 2025-03-06T10:42:15Z

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mlbridge · 2025-03-06T10:45:04Z

Webrevs

00: Full (6a2c0e53)

dholmes-ora

Abstracting this out seems reasonable to me, though I should say I thought we already used -pthread rather than -lpthread.

Needs build team approval before integrating.

snake66 · 2025-03-06T13:27:15Z

Abstracting this out seems reasonable to me, though I should say I thought we already used -pthread rather than -lpthread.

I noticed there were a few places that used -pthread by default. I left these alone in this PR.

vieiro · 2025-03-06T13:53:31Z

make/test/JtregNativeHotspot.gmk

-  BUILD_HOTSPOT_JTREG_LIBRARIES_LIBS_libnativeStack += -lpthread
-  BUILD_HOTSPOT_JTREG_LIBRARIES_LIBS_libTestUnloadedClass += -lpthread
-  BUILD_HOTSPOT_JTREG_EXECUTABLES_LIBS_exeGetCreatedJavaVMs := -lpthread
+  BUILD_HOTSPOT_JTREG_LIBRARIES_LIBS_libbootclssearch_agent += $(LIBPTREAD)


Hi. Should this read $(LIBPTHREAD) instead (i.e., missing H)?
Could be me too, I need new reading glasses...

You're absolutely right.

@snake66 Making changes to makefiles is tricky, since a misspelled variable do not get any warning but is just silently ignored.

For a change like this, that is a pure refactoring that is not supposed to change the output, I highly recommend using the COMPARE_BUILD system. Unfortunately, this is severely underdocumented. There is a short paragraph at https://openjdk.org/groups/build/doc/building.html under "Developing the Build System Itself", but in short, what I'd do is to create a diff files of these changes compared to a baseline (e.g. master, a specific build or commit), make sure you have the baseline checked out, and then run make jdk-image test-image COMPARE_BUILD=PATCH=my_patch.diff. This will build the targets twice, one without the patch and one with the patch, and then automatically run the compare script to analyze any differences. For this particular patch, there should be none. This would likely have caught this typo. (Given that the test-image is actually compared; I suddenly got a bit uncertain about that...)

@vieiro Thanks! That's well spotted, I'll fix!

@magicus Thanks for this info! I'll give it a try without fixing the typo first, to see if it would catch it.

erikj79 · 2025-03-06T14:11:11Z

/reviewers 2 reviewers

openjdk · 2025-03-06T14:12:11Z

@erikj79
The total number of required reviews for this PR (including the jcheck configuration and the last /reviewers command) is now set to 2 (with at least 2 Reviewers).

erikj79

What is the intended way of using this? Do you run make with LIBPTHREAD=-pthread or do you apply a patch on libraries.m4 for the specific way of linking to pthread?

erikj79 · 2025-03-06T14:15:38Z

make/autoconf/libraries.m4

@@ -139,7 +139,7 @@ AC_DEFUN_ONCE([LIB_SETUP_LIBRARIES],

  # Threading library
  if test "x$OPENJDK_TARGET_OS" = xlinux || test "x$OPENJDK_TARGET_OS" = xaix; then
-    BASIC_JVM_LIBS="$BASIC_JVM_LIBS -lpthread"
+    BASIC_JVM_LIBS="$BASIC_JVM_LIBS $(LIBPTHREAD)"


If you specifically need this to be resolved in the makefile rather than here, then please add a comment explaining why, otherwise use a shell script variable reference.

Suggested change

BASIC_JVM_LIBS="$BASIC_JVM_LIBS $(LIBPTHREAD)"

BASIC_JVM_LIBS="$BASIC_JVM_LIBS $LIBPTHREAD"

Yes, this is incorrect. Remember that m4 are shell scripts so you need to use shell syntax here. (I know it is confusing).

@erikj79 There will be a later patch to libraries.m4 that sets the variable based on the target platform, and then populates the LIBPTHREAD variable in spec.gmk. (https://github.com/openjdk/jdk/pull/23930/files#diff-56172cd2ec5804a5f764a6d0d5970da6144b024a06e008571f9822b2dc83cc36R147) That means the parenthesis should stay, right?

I'm not sure what you mean now. The link is to this very patch, which does what you describe -- sets LIBPTHREAD according to OS and stores it in spec.gmk.

And no, the paranthesis should not stay. If you keep them, the variable will be re-evaluated in make every time BASIC_JVM_LIBS is evaluated. That is not needed; by dropping the parenthesis the actual value to be used will be inserted as a string constant. Which is what we want, since we know the value at configure time.

magicus · 2025-03-06T15:47:58Z

What is the intended way of using this? Do you run make with LIBPTHREAD=-pthread or do you apply a patch on libraries.m4 for the specific way of linking to pthread?

This is in preparation of the upcoming BSD port, which uses -pthread instead of -pthread. It was me who suggested that this is done separately with the existing code, to minimize the patch of the BSD port.

magicus · 2025-03-06T15:56:43Z

make/Hsdis.gmk

@@ -127,7 +127,7 @@ ifeq ($(HSDIS_BACKEND), binutils)
    HSDIS_LDFLAGS += -L$(MINGW_GCC_LIB_PATH) -L$(MINGW_SYSROOT_LIB_PATH)
    MINGW_DLLCRT := $(MINGW_SYSROOT_LIB_PATH)/dllcrt2.o
    HSDIS_TOOLCHAIN_LIBS := $(MINGW_DLLCRT) -lmingw32 -lgcc -lgcc_eh -lmoldname \
-        -lmingwex -lmsvcrt -lpthread -ladvapi32 -lshell32 -luser32 -lkernel32
+        -lmingwex -lmsvcrt $(LIBPTHREAD) -ladvapi32 -lshell32 -luser32 -lkernel32
  else


The hsdis build is very weird and outside the normal integrated JDK build. I recommend you leave this instance alone. If you want to port hsdis to BSD you are likely to have to rewrite large parts of the compilation logic here anyway.

Ack, I'll drop that one from the patch.

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

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8351322: Parameterize link option for pthreads #23930

8351322: Parameterize link option for pthreads #23930

snake66 commented Mar 6, 2025 •

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snake66 Mar 6, 2025

	BASIC_JVM_LIBS="$BASIC_JVM_LIBS $(LIBPTHREAD)"
	BASIC_JVM_LIBS="$BASIC_JVM_LIBS $LIBPTHREAD"

8351322: Parameterize link option for pthreads #23930

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8351322: Parameterize link option for pthreads #23930

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