Created attachment 114264 [details] test case If two threads have the same current glX context, as permitted by GLX_MESA_multithread_makecurrent, then calling glXSwapIntervalMESA results in invoking dri2SetSwapInterval with the pdraw argument set to NULL. dri2SetSwapInterval then dereferences pdraw, causing a segmentation fault. The attached program reproduces this. You can also reproduce the same crash by letting a thread exit with a context bound and then making the context current on another thread and calling glXSwapIntervalMESA there (this seems a bit dirty, but if there is no requirement to unbind GL contexts before exiting threads, then this method doesn't require GLX_MESA_multithread_makecurrent). If you add -DTEST2 to the compiler flags when compiling the attached file, this crash will be reproduced instead. This affects at least Mesa 10.4.3, 10.5, and git master at revision 48b0a3c1c9d829a9b1d401afb2796b35df94a5d7.
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