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[SR-12492] Deadlock in swift_getTypeName TypeNameCacheLock #54934

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erichoracek opened this issue Apr 2, 2020 · 1 comment
Closed

[SR-12492] Deadlock in swift_getTypeName TypeNameCacheLock #54934

erichoracek opened this issue Apr 2, 2020 · 1 comment
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. standard library Area: Standard library umbrella

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@erichoracek
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Previous ID SR-12492
Radar None
Original Reporter @erichoracek
Type Bug
Status Closed
Resolution Invalid

Attachment: Download

Environment

OS Version: iPhone OS 13.4 (17E255)

Xcode: 11.3.1

Swift: 5.1

Additional Detail from JIRA
Votes 0
Component/s Standard Library
Labels Bug
Assignee None
Priority Medium

md5: a43a149b0c1c318249f717b017373141

Issue Description:

We're seeing the iOS watchdog killing our app due to the main thread being blocked by the TypeNameCacheLock readwrite lock in swift_getTypeName. Many background threads are blocked as well.

In the attached stacktrace, we have many threads in something like the following state:

0 libsystem_kernel.dylib 0x0000000185f7ec88 __psynch_rw_rdlock + 8
1 libsystem_pthread.dylib 0x0000000185ea4490 _pthread_rwlock_lock_wait + 72
2 libsystem_pthread.dylib 0x0000000185ea4424 _pthread_rwlock_lock_slow + 680
3 libswiftCore.dylib 0x0000000193ccfcf8 swift::ReadWriteLockPlatformHelper::readLock+ 3374328 (_opaque_pthread_rwlock_t&) + 24
4 libswiftCore.dylib 0x0000000193ca2cec swift_getTypeName + 88
5 libswiftCore.dylib 0x0000000193aa86fc typeName+ 1115900 (:qualified) + 28

We're working on mitigating this crash on our end by calling type(of) less frequently.
@erichoracek
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Turns out after much digging that this was due to an unrelated issue.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
This issue was closed.
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. standard library Area: Standard library umbrella
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@erichoracek