Park Darwin main thread in CFRunLoop for headed AWT/Swing to fix hang#13996
Open
The-Alchemist wants to merge 1 commit into
Open
Park Darwin main thread in CFRunLoop for headed AWT/Swing to fix hang#13996The-Alchemist wants to merge 1 commit into
The-Alchemist wants to merge 1 commit into
Conversation
Without libjli-equivalent CFRunLoop parking, SubstrateVM leaves pthread main in ThreadsLock.wait while Metal/CGL performSelector:waitUntilDone deadlocks (oracle#13994). Mirror OpenJDK libjli / Graal launcher ParkEventLoop behind -H:+DarwinParkMainInCFRunLoop (default off). Signed-off-by: The-Alchemist <karl@digital-alchemy.io>
oracle-contributor-agreement
Bot
added
the
OCA Verified
The-Alchemist
changed the title
The-Alchemist
changed the title
The-Alchemist
marked this pull request as ready for review
July 16, 2026 16:45
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Summary
Exploratory fix for Darwin headed AWT/Swing hang (#13994; related #4124).
After AWT dylibs/shims (#13282), native-image Swing still deadlocks because pthread main never enters an AppKit/CFRunLoop while Metal/CGL uses
performSelector:…waitUntilDone. HotSpot/libjli and Graalsdk/.../launcher.ccalready park the process main thread; SubstrateVMJavaMainWrapperdid not.This PR adds experimental
-H:+DarwinParkMainInCFRunLoopthat:runMainRoutinemachinery).CFRunLoopRunInMode(libjli /ParkEventLooppattern).runCore, waits for non-daemon threads + isolate shutdown on the side thread, thenLibC.exit(matches Darwinlauncher.cc).Test plan
mx buildsubstratevmnative-image -H:+UnlockExperimentalVMOptions -H:+DarwinParkMainInCFRunLoop -H:Preserve=module=java.desktop … MinimalSwingSwingUtilities.invokeLater+JFramewrites a ready marker (window path progresses; previously hung before UI)System.exitinteractionNonHeadlessJavaDesktopTestis Linux-only)Specifications
Notes for reviewers
LibC.exitvs cancelableCFRunLoopStop+ re-attach shutdown on the initial thread.sdk/src/org.graalvm.launcher.native/src/launcher.cc(ParkEventLoop) and OpenJDKlibjli/java_md_macosx.m.