fix: Swing Thread Lock during MMIO / Display Character

[javalosr2004]

Issue: Display Freeze during MMIO Output

Hi, I am opening a PR in regard to to an issue I was having when printing characters to MMIO, it would randomly freeze, the sp would always vary, so I took a look at the stack trace during program execution.

I also saw that someone else had a similar issue a couple years ago, but it was seemingly fixed: link here

Stack Trace

"RISCV" #55 [126983] prio=4 os_prio=31 cpu=389.33ms elapsed=261.90s tid=0x000000013d48c400 nid=126983 waiting for monitor entry [0x00000002fc641000]

java.lang.Thread.State: BLOCKED (on object monitor)

at java.awt.Component$AccessibleAWTComponent.getLocationOnScreen(java.desktop@21/Component.java:9802)
- waiting to lock <0x000000070042e9f0> (a java.awt.Component$AWTTreeLock)
at javax.swing.JComponent$AccessibleJComponent.getLocationOnScreen(java.desktop@21/JComponent.java:3735)
at javax.swing.text.JTextComponent$AccessibleJTextComponent.caretUpdate(java.desktop@21/JTextComponent.java:2622)
at javax.swing.text.JTextComponent.fireCaretUpdate(java.desktop@21/JTextComponent.java:408)
at javax.swing.text.JTextComponent$MutableCaretEvent.fire(java.desktop@21/JTextComponent.java:4484)
at javax.swing.text.JTextComponent$MutableCaretEvent.stateChanged(java.desktop@21/JTextComponent.java:4506)
at javax.swing.text.DefaultCaret.fireStateChanged(java.desktop@21/DefaultCaret.java:857)
at com.apple.laf.AquaCaret.fireStateChanged(java.desktop@21/AquaCaret.java:86)
at javax.swing.text.DefaultCaret.changeCaretPosition(java.desktop@21/DefaultCaret.java:1343)
at javax.swing.text.DefaultCaret.handleSetDot(java.desktop@21/DefaultCaret.java:1242)
at javax.swing.text.DefaultCaret.setDot(java.desktop@21/DefaultCaret.java:1223)
at javax.swing.text.DefaultCaret$Handler.insertUpdate(java.desktop@21/DefaultCaret.java:1819)
at javax.swing.text.AbstractDocument.fireInsertUpdate(java.desktop@21/AbstractDocument.java:227)
at javax.swing.text.AbstractDocument.handleInsertString(java.desktop@21/AbstractDocument.java:781)
at javax.swing.text.AbstractDocument.insertString(java.desktop@21/AbstractDocument.java:740)
at javax.swing.text.PlainDocument.insertString(java.desktop@21/PlainDocument.java:131)
at javax.swing.JTextArea.append(java.desktop@21/JTextArea.java:482)

**at rars.tools.KeyboardAndDisplaySimulator.displayCharacter(KeyboardAndDisplaySimulator.java:336)
at rars.tools.KeyboardAndDisplaySimulator.processRISCVUpdate(KeyboardAndDisplaySimulator.java:253)**

at rars.tools.AbstractToolAndApplication.update(AbstractToolAndApplication.java:480)
at java.util.Observable.notifyObservers(java.base@21/Observable.java:174)
at rars.riscv.hardware.Memory$MemoryObservable.notifyObserver(Memory.java:1126)
at rars.riscv.hardware.Memory.notifyAnyObservers(Memory.java:1156)
at rars.riscv.hardware.Memory.set(Memory.java:428)
at rars.riscv.hardware.Memory.setWord(Memory.java:500)
at rars.riscv.instructions.SW.store(SW.java:39)
at rars.riscv.instructions.Store.simulate(Store.java:57)
at rars.simulator.Simulator$SimThread.run(Simulator.java:484)
at java.lang.Thread.runWith(java.base@21/Thread.java:1596)
at java.lang.Thread.run(java.base@21/Thread.java:1583)

Solution

I simply used Swing's invokeLater function to queue up the display of a new character.