UI doesn't indicate each thread listed in the call stack as having been "PAUSED ON EXCEPTION" on loading core dump

[ayushsahay1837]

Version of VS Code: 1.67.2

OS: Ubuntu 18.04.6 LTS

Reproducible steps that cause the issue:

Have Visual Studio Code load a core dump in lldb via lldb-vscode (debug adapter for Visual Studio Code available as part of the LLDB project, which, to the best of my knowledge, is unpublished) by employing an attach configuration akin to the following –

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Post-mortem Debug",
            "type": "lldb-vscode",
            "request": "attach",
            "program": "${workspaceFolder}/a.out",
            "coreFile": "${workspaceFolder}/a.out.core"
        }
    ]
}

What I expect to see, versus what I actually see:

All threads in the process are stopped with reason exception –

...

{"body":{"allThreadsStopped":true,"preserveFocusHint":false,"reason":"exception","threadCausedFocus":true,"threadId":848},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":843},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":844},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":845},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":846},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":847},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":849},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":850},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":851},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":852},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":853},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":854},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":855},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":856},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":1881},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":1882},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":1883},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":1884},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":1886},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":1887},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":1888},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":1889},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":true,"preserveFocusHint":true,"reason":"exception","threadId":1890},"event":"stopped","seq":0,"type":"event"}

...

So, I'd expect the UI to indicate each thread listed in the call stack as having been PAUSED ON EXCEPTION. However, I see that the UI indicates only Thread # 23 as having been PAUSED ON EXCEPTION, and others as having been PAUSED –

What's curious, though, is that if allThreadsStopped is reported as false in each of the pertinent stopped events, then the UI indicates all threads in the call stack as having been PAUSED ON EXCEPTION –

...

{"body":{"allThreadsStopped":false,"preserveFocusHint":false,"reason":"exception","threadCausedFocus":true,"threadId":848},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":843},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":844},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":845},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":846},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":847},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":849},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":850},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":851},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":852},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":853},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":854},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":855},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":856},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":1881},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":1882},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":1883},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":1884},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":1886},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":1887},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":1888},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":1889},"event":"stopped","seq":0,"type":"event"}

{"body":{"allThreadsStopped":false,"preserveFocusHint":true,"reason":"exception","threadId":1890},"event":"stopped","seq":0,"type":"event"}

...

Kindly let me know in case any additional information is required.

[roblourens]

Initial investigation shows that this is from

vscode/src/vs/workbench/contrib/debug/browser/debugSession.ts

Line 892 in a803dc3

thread.stoppedDetails = thread.threadId === stoppedDetails.threadId ? stoppedDetails : { reason: undefined };

I think it essentially clears the previous pause reason when processing the allThreadsStopped. I think this could keep the previous stoppedDetails on the thread. But, isn't it odd to send allThreadsStopped if you are going to send individual stopped events for every thread anyway?

Kinda related to #70107

[ayushsahay1837]

@roblourens, I imagine that that's an implication of the design. Currently, LLDB supports only process-centric debugging. So, when any thread in a process stops, all the other threads are stopped too. I reckon that that's why lldb-vscode reports allThreadsStopped as true for every stopped event. However, AFAICT, lldb-vscode maintains neither a list nor the states of the processes and threads under debug, and relies on pertinent events broadcast by LLDB to report stopped events. Now, if I'm not wrong, then all the threads in a core dump are stopped. So, I'd expect LLDB to broadcast a pertinent event for each thread in a core dump, and lldb-vscode to consequently report stopped events for all the threads.

[roblourens]

Sure, that's fine. Seems correct for vscode to support this the way you're using it.

[ayushsahay1837]

@roblourens, thanks! 😁

BTW, is it too early for any work on this to be planned for a specific release? I only ask so that I can offer our customers a ballpark estimate of when they can expect the fix for this to become available. 😬

[roblourens]

How does next month sound? 😄

[roblourens]

And once the PR above is merged, and we have resumed shipping new Insiders after this week's release (should be by the end of the week, or next Monday), I'd appreciate you verifying that the issue is actually fixed

[ayushsahay1837]

@roblourens, sure, I'd be happy to! Thanks a lot for looking into this! 😁

[ayushsahay1837]

@roblourens, the UI indicates each thread listed in the call stack as having been PAUSED ON EXCEPTION in the latest release of Visual Studio Code Insiders.