Attachment 85595 Details for Bug 69200 – Patch to add locks to builtin_builder::initialize()

[patch] Patch to add locks to builtin_builder::initialize()

0001-glsl-Add-locking-to-builtin_builder-initialize.patch (text/plain), 1.78 KB, created by Kenneth Graunke on 2013-09-11 02:22:52 UTC

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Creator: Kenneth Graunke

Created: 2013-09-11 02:22:52 UTC

Size: 1.78 KB

patch

obsolete

>From 63b5fb1b30b779a42e9e23a67a26366ac4afcd91 Mon Sep 17 00:00:00 2001
>From: Kenneth Graunke <kenneth@whitecape.org>
>Date: Tue, 10 Sep 2013 14:55:42 -0700
>Subject: [PATCH] glsl: Add locking to builtin_builder::initialize().
>
>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.
>
>Fixes sporadic failures in Piglit's glx-multithread-shader-compile.
>
>Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
>---
> src/glsl/builtin_functions.cpp | 15 +++++++++------
> 1 file changed, 9 insertions(+), 6 deletions(-)
>
>diff --git a/src/glsl/builtin_functions.cpp b/src/glsl/builtin_functions.cpp
>index ce78df1..bc539ef 100644
>--- a/src/glsl/builtin_functions.cpp
>+++ b/src/glsl/builtin_functions.cpp
>@@ -565,13 +565,16 @@ builtin_builder::find(_mesa_glsl_parse_state *state,
> void
> builtin_builder::initialize()
> {
>-   /* If already initialized, don't do it again. */
>-   if (mem_ctx != NULL)
>-      return;
>+   _glthread_DECLARE_STATIC_MUTEX(builtin_init_lock);
>+   _glthread_LOCK_MUTEX(builtin_init_lock);
> 
>-   mem_ctx = ralloc_context(NULL);
>-   create_shader();
>-   create_builtins();
>+   if (mem_ctx == NULL) {
>+      mem_ctx = ralloc_context(NULL);
>+      create_shader();
>+      create_builtins();
>+   }
>+
>+   _glthread_UNLOCK_MUTEX(builtin_init_lock);
> }
> 
> void
>-- 
>1.8.3.4
>

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Attachments on bug 69200: 85595 | 93519

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