gpus_ReturnGuiltyForHardwareRestart crash (consistently reproducible).

[mb12]

I had filed a bug for this issue earlier (Issue #1198 #1198). At that time I did not have consistent steps to reproduce the issue. I've finally isolated the problem to a very trivial style file and a vector source that consistently reproduces the problem.
This crash is consistently reproducible with the following configuration:

1. iPhone 5 running iOS 8.1.3 (It reproduces only on iPhone 5 and this OS version).

It does not reproduce on other device/OS configurations. I've tested on iPhone 4s(7.x) , iPhone 6(8.3), iPad(8.1.3) and iPad Air (8.3)

Steps to reproduce:

1. In you git repo with sample test app copy over the style file at this link to an existing existing style (say emerald-v7.json)

http://54.227.241.87/static_html/test_grid_pbfs/style.json
2. Launch the sample test app. Switch to the new style.
3. Go to zoom level 4.
4. Pan / pan with flick.

Testapp crashes within a few seconds.

Details on what the style/source does.

1. This style draw a grid of 8x8 squares at zoom level 4.
2. The tile pbf is very trivial. It has 64 areas for each square. It also has lines marking the boundary of each square.

[1ec5]

ref #1460

[mb12]

#1460 is a different issue. #1460 is related to open gl calls not being disabled when app moves to background.

This issue consistently causes a crash when rendering a trivial grid of squares on iPhone 5.

[mb12]

Even on devices where it does not crash, the fill-color is inaccurate. The expected behavior is that all grid squares would be rendered with yellow translucent color. But only half of the grid squares are rendered with this color.
If I change the opacity to 1, then all the grid squares are rendered with yellow color. It looks like there is an issue with rendering fill areas with translucency (opacity < 1).

[mb12]

I was able to get hold of a different iPhone 5 with a slightly different OS version (iOS 8.1.2) and it crashes on that device as well. Is it possible for someone to do some analysis on this? I have hit a dead end on this one.

[friedbunny]

I'm inclined to blame this on a bug in the GPU driver for the PowerVR SGX543 series (with RC2 seeming to mean "Release Candidate 2"?). The actual name of the iPhone 5 GPU is SGX543MP3.

But this crash doesn't reproduce on the iPad mini (SGX543MP2), iOS 8.3, which is a very similar GPU but with two cores (versus three for SGX543MP3). SGX543MP2 was also used in iPhone 4S and iPad 2, so I'd expect those not to crash, either.

Also does not reproduce on iPhone 4 (SGX535), iOS 7.1.2.

[mb12]

@friedbunny Thanks for the comment.

However on the same hardware where the crash reproduces, the following causes it go away:

• If I reduce the number of fill bucket /styles to a small number. The current style I have provided renders a grid of 64 squares (8x8 grid) at zoomlevel four. If I reduce this number to 4, the crash goes away.
• This particular style also uses a translucent opacity (0.5 in all the cases). If I increase it to 1, the crash goes away (when there is only one vector Source). The reason I mention one vector source here is because that is what I've provided in the test case.
• The crash happens almost instantaneously only during panning / changing device orientation (that forces re-render).

This leads me to believe there is some issue with alpha rendering for fill buckets.

PS: I upgraded one of the iPhone 5 devices to 8.3. The crash still reproduces on that device.

[friedbunny]

Here's one story of debugging gpus_ReturnGuiltyForHardwareRestart.

[mb12]

@incanus Is it possible to add this to list of issues for analysis in ios beta 2? This is a consistently reproducible crash in gl-core.

[jfirebaugh]

Does this still happen?

[mb12]

Yes. It crashed the last time I tried it (a couple of weeks back).

[ohlsont]

Is this the same bug? Also iPhone 5 but on iOS 9.3. I have a few thousand polygons and a few thousand point annotations in the form of a building so the zoom is ~18 when crashing. I don't get this on iPhone 6 or 6s.

[1ec5]

@Hinken, what version of the Mapbox iOS SDK are you using? Also, does this crash occur when the application is in the foreground or when it's in the background or background mode? The crash trace looks a bit different than the one @mb12 posted in #1198.

[ohlsont]

Im using a bit modified version where I use the stylesheet for styling instead of the delegate callbacks. But the rest is merged with your master branch with the latest release. It happens in the foreground. I realise I should have mentioned that, but maybe you have some use of this anyway :). Thanks for your great work here