Mesa (10.1): glsl: Add locking to builtin_builder singleton

[Ian Romanick]

Module: Mesa
Branch: 10.1
Commit: 69bd4ed017f7cc8bae20fb6da0aba249025b0776
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=69bd4ed017f7cc8bae20fb6da0aba249025b0776

Author: Daniel Kurtz <djkurtz at chromium.org>
Date:   Fri Feb  7 19:29:06 2014 +0800

glsl: Add locking to builtin_builder singleton

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.

Bugzilla: https://bugs.freedesktop.org/69200
Signed-off-by: Daniel Kurtz <djkurtz at chromium.org>
Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
Cc: "10.1 10.0" <mesa-stable at lists.freedesktop.org>
(cherry picked from commit b47d231526821f5cff99546a984103a7222bc66c)

---

 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 *