Crash when deleting buffers

[kkaefer]

I'm seeing a fairly frequent crash bug that happens randomly during buffer deletion. The buffer IDs are valid and do exist.

What could be happening is that we have an OpenGL context loss that we're ignoring, which invalidates all of the buffers.

[robipresotto]

buffer.hpp line 24
mbgl::VectorTileData::~VectorTileData()

[ljbade]

Hmm the major problem is the GL implementation should never crash. It is supposed to check for bad state and return a GL error instead.

[kkaefer]

After some debugging, it looks like the following is happening:

• The GLKView has its (internal) display method run, which triggers the (internal) setFramebuffer method. This likely activates the context on the main thread and runs OpenGL functions for framebuffer creating/attaching.
• Typically this is fine since we're not running OpenGL code unless the main thread tells us to, except:
• At the same time, the Map thread runs a shared_ptr destructor of a DebugBucket object, which in turn deletes the VAO and associated OpenGL objects

Here's my proposed change: Instead of directly deleting all OpenGL objects, we should accumulate the IDs and delete them during the next render step.

[mb12]

Why does the stack trace have ~LiveTileData in the back trace. Is there some code path that triggers invalidateTiles outside mapThread?

[kkaefer]

~LiveTileData is run in the map thread

[incanus]

Cross-ref to #1022 — I will double-check that things are kosher here.

[picciano]

+1 Awesome, no more crashing. Thanks!

[kkaefer]

This crashes in Debug mode since the Worker threads are now joined from the wrong thread.

[kkaefer]

Fixed in 9d30d40