Crash in background — glFinish_Exec, gpus_ReturnNotPermittedKillClient, libGPUSupportMercury

[picciano]

I started seeing these that past two days. This was from Crashlytics, so not exactly sure what user was doing at the time.

Thread : Crashed: com.apple.main-thread
0  libGPUSupportMercury.dylib     0x000000018c389f90 gpus_ReturnNotPermittedKillClient + 12
1  libGPUSupportMercury.dylib     0x000000018c38af40 gpusSubmitDataBuffers + 172
2  GLEngine                       0x0000000187078664 glFinish_Exec + 132
3  GLKit                          0x000000018446004c -[GLKView _display:] + 200
4  QuartzCore                     0x0000000187777a34 CA::Layer::display() + 148
5  QuartzCore                     0x0000000187758a7c CA::Layer::display_if_needed(CA::Transaction*) + 244
6  QuartzCore                     0x0000000187758734 CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 44
7  QuartzCore                     0x0000000187757ebc CA::Context::commit_transaction(CA::Transaction*) + 276
8  QuartzCore                     0x0000000187757c3c CA::Transaction::commit() + 528
9  UIKit                          0x0000000187e0c56c _afterCACommitHandler + 152
10 CoreFoundation                 0x00000001833902a4 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 32
11 CoreFoundation                 0x000000018338d230 __CFRunLoopDoObservers + 360
12 CoreFoundation                 0x000000018338d610 __CFRunLoopRun + 836
13 CoreFoundation                 0x00000001832b92d4 CFRunLoopRunSpecific + 396
14 GraphicsServices               0x000000018cacf6fc GSEventRunModal + 168
15 UIKit                          0x0000000187e7efac UIApplicationMain + 1488
16 TallyGo                        0x00000001001284f0 main (main.m:14)
17 libdyld.dylib                  0x000000019527aa08 start + 4

[friedbunny]

This looks suspiciously similar to the two crashes discussed in #1198, but not quite. @picciano, do you see any hardware/OS patterns for these crashes?

[picciano]

I've been seeing it on iPhone 6, iOS versions 8.2 and 8.3. This build is using the MBGL codebase from Monday, May 4, late afternoon.

[friedbunny]

It looks like gpus_ReturnNotPermittedKillClient usually means that the app is trying to render OpenGL in the background, says Apple and variety of Stack Overflow threads (like this one).

Here is effectively the same crash on VLC's iOS app. It appears they fixed it by checking for a broader range of background notifications.

[friedbunny]

@incanus just hardened iOS backgrounding behavior yesterday in #1451. We don't handle UIApplicationWillTerminateNotification, but I'm not sure we need to?

[incanus]

I don't think we need to hit UIApplicationWillTerminateNotification.

We are still seeing this crash internally, though not in a way that looks like a crash to anyone (because of the state-saving nature of backgrounding). Currently trying to work out what exactly the repro is.

[incanus]

http://stackoverflow.com/a/15814933/977220

I now keep track of the state of the status bar in relation to the app's active status, and only animate if the application state is UIApplicationStateActive. Having done this, I haven't had a crash since.

[picciano]

According to Crashlytics, the app was not in background. But perhaps it's just a reporting/timing glitch?

[incanus]

Hmm, @picciano, any way you could share some of the log around that, or explain how you know?

[picciano]

See screen shot image pasted in above message. Crashlytics is reporting 100% of the 8 crashes were with "app in focus".

[1ec5]

Does Crashlytics rely on the same UIApplicationDidEnterBackgroundNotification/UIApplicationWillEnterForegroundNotification notifications we’ve been using? If so, it’d be misreporting exactly these crashes as being “while in focus”.

[incanus]

We just can't seem to repro this internally. We are "seeing" the crash in Hockey, but no one is reporting any crash problems and we can't repro in Xcode. Maybe we can punt on this?