sentry-cocoa
sentry-cocoa copied to clipboard
getsentry
Hang during initialization when SentrySDK.addBreadcrumb() is called from different thread
Platform
iOS
Environment
TestFlight
Installed
Carthage
Version
8.24.0
Did it work on previous versions?
8.21.0
Steps to Reproduce
The issue was only reproducible in TestFlight / AppStore builds, not in DEBUG. It was reproduced with 8.24.0 and 8.23.0. Didn't try 8.22.0. Not reproducible with 8.21.0.
- Launch the app
- Force-quit (kill) the app
- Run the app and wait as it hangs
The SDK is initialized through the usual Swift call:
SentrySDK.start { options in ... }
The breadcrumb is logged from a different thread (synchronous dispatch queue)
private lazy var cookiesSyncQueue = DispatchQueue(label: "CookieManagerSyncQueue")
cookiesChangeStream = NotificationCenter.default
.publisher(for: .NSHTTPCookieManagerCookiesChanged, object: rawStorage)
.throttle(for: 0.1, scheduler: cookiesSyncQueue, latest: true)
.sink { _ in
let breadcrumb = ...
SentrySDK.addBreadcrumb(breadcrumb)
}
Other notes
- Commenting out the breadcrumb call from the other dispatch queue works.
- Since it was reproduced in 8.23.0, but not in 8.21.0, this PR might be related https://github.com/getsentry/sentry-cocoa/pull/3698
Expected Result
The app launches without a hang.
Actual Result
The app hangs and gets killed by the watchdog after 20 seconds.
In the ips file, both threads hang with -[SentryCrashWrapper systemInfo] at the top of the trace. Here are the excerpts:
Main thread:
0 libsystem_kernel.dylib 0x1e266293c __ulock_wait2 + 8
1 libsystem_platform.dylib 0x1f6028ea8 _os_unfair_lock_lock_slow + 188
2 libobjc.A.dylib 0x1920138b8 objc_sync_enter + 20
3 kphone 0x102ac5224 +[SentrySDK options] (in kphone) + 24 + 7918116
4 kphone 0x102ad5508 -[SentryDependencyContainer crashReporter] (in kphone) + 88 + 7984392
5 kphone 0x102a7e10c __32-[SentryCrashWrapper systemInfo]_block_invoke (in kphone) + 40 + 7627020
6 libdispatch.dylib 0x1a1ff6dd4 _dispatch_client_callout + 20
7 libdispatch.dylib 0x1a1ff8654 _dispatch_once_callout + 32
8 kphone 0x102a7e0e0 -[SentryCrashWrapper systemInfo] (in kphone) + 60 + 7626976
9 kphone 0x102a7e258 -[SentryCrashWrapper enrichScope:] (in kphone) + 164 + 7627352
10 kphone 0x102a96f14 -[SentryHub initWithClient:andScope:] (in kphone) + 736 + 7728916
11 kphone 0x102ac5768 +[SentrySDK startWithOptions:] (in kphone) + 640 + 7919464
12 kphone 0x102ac5db4 +[SentrySDK startWithConfigureOptions:] (in kphone) + 88 + 7921076
Thread 2:
0 libsystem_kernel.dylib 0x1e2656578 __ulock_wait + 8
1 libdispatch.dylib 0x1a1ff77c4 _dlock_wait + 56
2 libdispatch.dylib 0x1a1ff76f4 _dispatch_once_wait + 112
3 kphone 0x102a7e0e0 -[SentryCrashWrapper systemInfo] (in kphone) + 60 + 7626976
4 kphone 0x102a7e258 -[SentryCrashWrapper enrichScope:] (in kphone) + 164 + 7627352
5 kphone 0x102a96f14 -[SentryHub initWithClient:andScope:] (in kphone) + 736 + 7728916
6 kphone 0x102ac51bc +[SentrySDK currentHub] (in kphone) + 60 + 7918012
7 kphone 0x102ac6b3c +[SentrySDK addBreadcrumb:] (in kphone) + 40 + 7924540
Are you willing to submit a PR?
No response
I tried to reproduce this by adding breadcrumbs on a dispatch queue directly before starting the SDK but was unable to reproduce the issue:
let dispatchSerial = DispatchQueue(label: "queue")
for _ in 0..<100 {
dispatchSerial.async {
let crumb = Breadcrumb()
crumb.message = "hello"
SentrySDK.addBreadcrumb(crumb)
}
}
SentrySDK.start(configureOptions: { options in
// ...
It looks like the locks of both threads end up in a deadlock. So both SentrySDK currentHub and [SentrySDK options] require a lock to self in SentrySDK. https://github.com/getsentry/sentry-cocoa/blob/d6ff82cd1e1d0d263fb1a7358b09bd0a08df013e/Sources/Sentry/SentrySDK.m#L73-L88
That could be the culprit, but I would like to get a repro if possible so that we can fix it properly. @juraj-blahunka, how often does this happen? Every time or only from time to time? When do you call this code snipped?
private lazy var cookiesSyncQueue = DispatchQueue(label: "CookieManagerSyncQueue")
cookiesChangeStream = NotificationCenter.default
.publisher(for: .NSHTTPCookieManagerCookiesChanged, object: rawStorage)
.throttle(for: 0.1, scheduler: cookiesSyncQueue, latest: true)
.sink { _ in
let breadcrumb = ...
SentrySDK.addBreadcrumb(breadcrumb)
}
@philipphofmann thank you for looking into it!
I've been trying to reproduce with a similar code in DEBUG but also failed. I was only able to reproduce when the debugger isn't attached (in TestFlight builds) and I get it to hang in ~70% of cases after force killing the app.
Everything happens from one method (simplified):
func application(_ application: UIApplication, willFinishLaunchingWithOptions ... {
cookiesChangeStream = NotificationCenter.default.publisher(for: .NSHTTPCookieManagerCookiesChanged, object: rawStorage) ... // where the sink adds breadcrumbs
SentrySDK.start { ... }
@juraj-blahunka, we will address the issues pointed out in https://github.com/getsentry/sentry-cocoa/issues/3899#issuecomment-2077302631 because we should address them anyways. Maybe they fix your problem if not we need to investigate further.
This is related to https://github.com/getsentry/sentry-cocoa/issues/3956.