On Wed, 10 Jan 2024 14:54:47 GMT, Kevin Rushforth <k...@openjdk.org> wrote:
> As described in the JBS bug, there is a long-standing deadlock that happens > on macOS between the AWT EDT and the JavaFX Application thread (which on > macOS is the AppKit thread) when processing Input Method Events (IME) in a > WebView node in a JFXPanel. > > This PR fixes the deadlock by adding `"AWTRunLoopMode"` to the list of modes > that will accept the calls to `performSelectorOnMainThread` used by > `_submitForLaterInvocation` and `_invokeAndWait`. These two native methods > are the macOS implemention `runLater` and `runAndWait`, respectively, and are > used to run Java Runnables on the JavaFX Application Thread. > > This deadlock is happening much more often on recent macOS versions, and in > macOS 14, pressing CAPS LOCK is sufficient to trigger IME calls. > > The OS calls the AWT IME methods on the AppKit thread, which is also the > JavaFX Application Thread. The AWT IME callback methods, for example > `characterIndexForPoint`, call invokeAndWait to run the IME handler on the > AWT Event thread. In the case of JFXPanel, the registered IME handler is in > JavaFX code and we often need to run something on the JavaFX Application > Thread to avoid threading problems or crashes. See > [JDK-8196011](https://bugs.openjdk.org/browse/JDK-8196011) and > [JDK-8322703](https://bugs.openjdk.org/browse/JDK-8322703). > > A similar deadlock was observed while trying to fix a threading problem in > JFXPanel's handling of the IME calls as described in > [JDK-8322784](https://bugs.openjdk.org/browse/JDK-8322784), so it isn't > necessarily limited to using WebView. > > Anton Tarasov @forantar proposed a fix (in a comment in the JBS bug) in AWT > that would change the invokeAndWait calls used by the IME methods in > CInputMethod to call `doAWTRunLoop` with the `processEvents` flag set to > true, which will allow all events to be processed while in `doAWTRunLoop`. > > NOTE: I had created Draft PR openjdk/jdk#17290 with Anton's proposed fix, > expanded to cover all of the cases, but during the discussion it was pointed > out that `doAWTRunLoop` should already be able to run selectors via > `performSelectorOnMainThread` -- see [this > comment](https://github.com/openjdk/jdk/pull/17290#issuecomment-1880001813). > The reason `doAWTRunLoop` doesn't process our messages is that it runs the > loop in a mode that only handles messages that include a custom > `"AWTRunLoopMode"` mode. > > Adding `"AWTRunLoopMode"` to the `performSelectorOnMainThread` calls used by > `_submitForLaterInvocation` and `_invokeAndWait` allows them to run when in... NOTE to reviewers: If you want to test this with WebView in a JFXPanel, you will also need the fix for [JDK-8322703](https://bugs.openjdk.org/browse/JDK-8322703), which is under review in PR #1321 to avoid a crash (that crash was effectively hidden by this deadlock so it was missed earlier). I have created a test branch that has both fixes: https://github.com/kevinrushforth/jfx/tree/test-8221261-8322703 You can either fetch that branch or fetch both PR branches and build. It is not necessary to build the native WebKit if you have an up-to-date library in your cache. ------------- PR Comment: https://git.openjdk.org/jfx/pull/1327#issuecomment-1885311069
