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There is currently no protection against walking a hash (using _mesa_HashWalk()) and modifying it at the same time, for instance by inserting or deleting elements. This leads to segfaults in multithreaded code if e.g. someone calls glTexImage2D (which may have to walk the list of FBOs) while another thread is calling glDeleteFramebuffers on another thread with the two contexts sharing lists. The reason for this is that _mesa_HashWalk() doesn't actually take the mutex that normally protects the hash; it takes an entirely different mutex. Thus, walks are only protected against other walks, and there is also no outer lock taking this. There is an old comment saying that this is to fix problems with deadlock if the callback needs to take a mutex; we solve this by changing the mutex to be recursive. A demonstration Helgrind hit from a real application: ==13412== Possible data race during write of size 8 at 0x3498C6A8 by thread #1 ==13412== Locks held: 2, at addresses 0x1AF09530 0x2B3DF400 ==13412== at 0x1F040C99: _mesa_hash_table_remove (hash_table.c:395) ==13412== by 0x1EE98174: _mesa_HashRemove_unlocked (hash.c:350) ==13412== by 0x1EE98174: _mesa_HashRemove (hash.c:365) ==13412== by 0x1EE2372D: _mesa_DeleteFramebuffers (fbobject.c:2669) ==13412== by 0x6105AA4: movit::ResourcePool::cleanup_unlinked_fbos(void*) (resource_pool.cpp:473) ==13412== by 0x610615B: movit::ResourcePool::release_fbo(unsigned int) (resource_pool.cpp:442) [...] ==13412== This conflicts with a previous read of size 8 by thread #20 ==13412== Locks held: 2, at addresses 0x1AF09558 0x1AF73318 ==13412== at 0x1F040CD9: _mesa_hash_table_next_entry (hash_table.c:415) ==13412== by 0x1EE982A8: _mesa_HashWalk (hash.c:426) ==13412== by 0x1EED6DFD: _mesa_update_fbo_texture.part.33 (teximage.c:2683) ==13412== by 0x1EED9410: _mesa_update_fbo_texture (teximage.c:3043) ==13412== by 0x1EED9410: teximage (teximage.c:3073) ==13412== by 0x1EEDA28F: _mesa_TexImage2D (teximage.c:3105) ==13412== by 0x166A68: operator() (mixer.cpp:454) There are many more interactions than just these two possible. Cc: 11.2 12.0 13.0 <mesa-stable@lists.freedesktop.org> Signed-off-by: Steinar H. Gunderson <steinar+mesa@gunderson.no> Reviewed-by: Timothy Arceri <timothy.arceri@collabora.com> |
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| src | ||
| .dir-locals.el | ||
| .editorconfig | ||
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| appveyor.yml | ||
| autogen.sh | ||
| CleanSpec.mk | ||
| common.py | ||
| configure.ac | ||
| install-gallium-links.mk | ||
| install-lib-links.mk | ||
| Makefile.am | ||
| REVIEWERS | ||
| SConstruct | ||
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File: docs/README.WIN32 Last updated: 21 June 2013 Quick Start ----- ----- Windows drivers are build with SCons. Makefiles or Visual Studio projects are no longer shipped or supported. Run scons libgl-gdi to build gallium based GDI driver. This will work both with MSVS or Mingw. Windows Drivers ------- ------- At this time, only the gallium GDI driver is known to work. Source code also exists in the tree for other drivers in src/mesa/drivers/windows, but the status of this code is unknown. Recipe ------ Building on windows requires several open-source packages. These are steps that work as of this writing. - install python 2.7 - install scons (latest) - install mingw, flex, and bison - install pywin32 from here: http://www.lfd.uci.edu/~gohlke/pythonlibs get pywin32-218.4.win-amd64-py2.7.exe - install git - download mesa from git see http://www.mesa3d.org/repository.html - run scons General ------- After building, you can copy the above DLL files to a place in your PATH such as $SystemRoot/SYSTEM32. If you don't like putting things in a system directory, place them in the same directory as the executable(s). Be careful about accidentially overwriting files of the same name in the SYSTEM32 directory. The DLL files are built so that the external entry points use the stdcall calling convention. Static LIB files are not built. The LIB files that are built with are the linker import files associated with the DLL files. The si-glu sources are used to build the GLU libs. This was done mainly to get the better tessellator code. If you have a Windows-related build problem or question, please post to the mesa-dev or mesa-users list.