| Summary: | OSX 10.9.5: Crash using master GLContext with multiple threads using GLContext sharing with master | ||
|---|---|---|---|
| Product: | [JogAmp] Jogl | Reporter: | Sven Gothel <sgothel> |
| Component: | macosx | Assignee: | Sven Gothel <sgothel> |
| Status: | RESOLVED FIXED | ||
| Severity: | enhancement | ||
| Priority: | --- | ||
| Version: | 2.3.0 | ||
| Hardware: | All | ||
| OS: | macosx | ||
| Type: | DEFECT | SCM Refs: |
245605eb760f6c1301d58a252fb6465a064ae19f
fe999abe4cb142b814e700d88e9f148ecb0ae4f0
5d3b7dc83c04e2c626a635eb3d143710f7ef4db2
73654365e6147a5eabe8747e5f4802b1fba83829
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| Workaround: | --- | ||
|
Description
Sven Gothel
2014-10-05 04:29:57 CEST
Related ARB_robustness: - https://www.opengl.org/registry/specs/ARB/robustness.txt, - Section Overview - Paragraph 5 "Multi-threaded use of OpenGL contexts in a "share group" allow sharing of objects such as textures and programs. Such sharing in conjunction with concurrent OpenGL commands stream execution by two or more contexts introduces hazards whereby one context can change objects in ways that can cause buffer overflows for another context's OpenGL queries." On OSX 10.9.5 using multiple GLContext, sharing a common master,
each rendering in their own thread (multithreading),
causes a crash.
I added experimental locking of the ShareSet in
GLContextImpl.makeCurrent()/release()
which removes the crash.
However, such ShareSet locking is too invasive:
- may deadlocks multithreaded creation/usage,
e.g. in GLMediaPlayerImpl (Animator vs StreamWorker)
- removes benefits of multithreading usage
Further analysis:
- OSX 10.9.5 not always crashes utilizing multithreaded shared contexts
- GLMediaPlayerImpl does not crash due to proper use of RingBuffer*,
which adds implicit lock-free object queuing (put/take).
- GearsES2 does crash due to concurrent draw commands of the 'slaves'
using the 'master' VBO objects,
even though such objects are created before concurrent read-only access
and immutable afterwards.
Resolution:
- Adding new GLRendererQuirk.NeedSharedObjectSync
- _NOT_ handling this quirk in our API directly,
i.e. not implementing above mentioned ShareSet locking.
- User is required to synchronize access of shared GL objects,
for drivers exposing GLRendererQuirk.NeedSharedObjectSync
- Adding a note to GLSharedContextSetter
+++
GLSharedContextSetter#synchronization GL Object Synchronization
Usually synchronization of shared GL objects should not be required,
if the shared GL objects are created and immutable before concurrent usage.
However, using drivers exposing GLRendererQuirks.NeedSharedObjectSync
always require the user to synchronize access of shared GL objects.
Synchronization can be avoided if accessing the shared GL objects
exclusively via a queue or com.jogamp.common.util.Ringbuffer,
see GLMediaPlayerImpl as an example.
+++
(*) == preliminary commits for unit testing
and providing a clean patch addressing the issue only.
+++
245605eb760f6c1301d58a252fb6465a064ae19f (*)
Shared Gears* Unit Tests: Align all 3 Gears* implementation
to use a shared Gears* object
+++
fe999abe4cb142b814e700d88e9f148ecb0ae4f0 (*)
Bug 1088: Fix ant test target 'junit.run.sharedctx':
Reuse generalized 'generic.junit.run.newt.headless', 'generic.junit.run.awt', ..
+++
5d3b7dc83c04e2c626a635eb3d143710f7ef4db2 (*)
GLRendererQuirks: Align wording in API doc
+++
73654365e6147a5eabe8747e5f4802b1fba83829
Add GLRendererQuirks.NeedSharedObjectSync; Tests: Synchronize GL objects if GLRendererQuirks.NeedSharedObjectSync is set.
^^ actual fix, as described.
+++
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