Consider a multithreaded program with two contexts A and B, and the following scenario:
1. Context A calls initialize(), which allocates mem_ctx and starts building built-ins. 2. Context B calls initialize(), which sees mem_ctx != NULL and assumes everything is already set up. It returns. 3. Context B calls find(), which fails to find the built-in since it hasn't been created yet. 4. Context A finally finishes initializing the built-ins. This will break at step 3. Adding a lock ensures that subsequent callers of initialize() will wait until initialization is actually complete. Similarly, if any thread calls release while another thread is still initializing, or calling find(), the mem_ctx/shader would get free'd while from under it, leading to corruption or use-after-free crashes. Fixes sporadic failures in Piglit's glx-multithread-shader-compile as reported in: https://bugs.freedesktop.org/69200 Signed-off-by: Kenneth Graunke <kenn...@whitecape.org> Signed-off-by: Daniel Kurtz <djku...@chromium.org> --- src/glsl/builtin_functions.cpp | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/src/glsl/builtin_functions.cpp b/src/glsl/builtin_functions.cpp index aeb8e5d..2162baa 100644 --- a/src/glsl/builtin_functions.cpp +++ b/src/glsl/builtin_functions.cpp @@ -4100,6 +4100,7 @@ builtin_builder::_mid3(const glsl_type *type) /* The singleton instance of builtin_builder. */ static builtin_builder builtins; +_glthread_DECLARE_STATIC_MUTEX(builtins_lock); /** * External API (exposing the built-in module to the rest of the compiler): @@ -4108,20 +4109,28 @@ static builtin_builder builtins; void _mesa_glsl_initialize_builtin_functions() { + _glthread_LOCK_MUTEX(builtins_lock); builtins.initialize(); + _glthread_UNLOCK_MUTEX(builtins_lock); } void _mesa_glsl_release_builtin_functions() { + _glthread_LOCK_MUTEX(builtins_lock); builtins.release(); + _glthread_UNLOCK_MUTEX(builtins_lock); } ir_function_signature * _mesa_glsl_find_builtin_function(_mesa_glsl_parse_state *state, const char *name, exec_list *actual_parameters) { - return builtins.find(state, name, actual_parameters); + ir_function_signature * s; + _glthread_LOCK_MUTEX(builtins_lock); + s = builtins.find(state, name, actual_parameters); + _glthread_UNLOCK_MUTEX(builtins_lock); + return s; } gl_shader * -- 1.9.0.rc1.175.g0b1dcb5 _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
