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Swift LLDB hangs for over an hour with 100% for a single frame variable --show-all-children [macOS & Linux] #4895

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@weissi

Description

@weissi

Repro

git clone https://github.com/apple/swift-nio
cd swift-nio && git reset --hard e2c7fa4d4bda7cb7f4150b6a0bd69be2a54ef8c4

swift build --build-tests
lldb  -- .build/debug/swift-nioPackageTests.xctest

(lldb) break set -o true -f MultiThreadedEventLoopGroup.swift -l 115
(lldb) run
(lldb) frame variable --show-all-children

Expected

Print all variables

Actual

(lldb) run
Process 28 launched: '/Users/johannes/devel/swift-nio/.build/debug/swift-nioPackageTests.xctest' (x86_64)
Test Suite 'All tests' started at 2022-06-28 14:40:37.420
Test Suite 'debug.xctest' started at 2022-06-28 14:40:37.421
Test Suite 'AcceptBackoffHandlerTest' started at 2022-06-28 14:40:37.421
Test Case 'AcceptBackoffHandlerTest.testECONNABORTED' started at 2022-06-28 14:40:37.421
Process 28 stopped
* thread #5, name = 'NIO-ELT-0-#0', stop reason = one-shot breakpoint 1
    frame #0: 0x0000555555ba4fc9 swift-nioPackageTests.xctest`closure #1 in closure #1 in static MultiThreadedEventLoopGroup.setupThreadAndEventLoop(l=0x00007fffe0005990, lock=0x0000555556b466b0, _loop=nil, loopUpAndRunningGroup=0x0000555556a99860) at MultiThreadedEventLoopGroup.swift:115:22
   112 	                                                   canEventLoopBeShutdownIndividually: false, // part of MTELG
   113 	                                                   selectorFactory: selectorFactory,
   114 	                                                   initializer: initializer) { l in
-> 115 	                lock.withLock {
   116 	                    _loop = l
   117 	                }
   118 	                loopUpAndRunningGroup.leave()
Target 0: (swift-nioPackageTests.xctest) stopped.
(lldb) frame variable --show-all-children
[hang forever, consuming 100% CPU]

Versions

docker.io/swiftlang/swift:nightly-5.7-focal
Swift version 5.7-dev (LLVM eecf02df5133efe, Swift ad06e7d7251311a)
Target: x86_64-unknown-linux-gnu

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