[gegl] buffer: protect sampler with mutex

[Øyvind Kolås <ok src gnome org>]

commit 3daef79984f52093829799c78b77834efebcbdb0
Author: Øyvind Kolås <pippin gimp org>
Date:   Tue Jul 1 07:03:40 2014 +0200

    buffer: protect sampler with mutex

 gegl/buffer/gegl-sampler.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/gegl/buffer/gegl-sampler.c b/gegl/buffer/gegl-sampler.c
index 39ae96d..fd4120b 100644
--- a/gegl/buffer/gegl-sampler.c
+++ b/gegl/buffer/gegl-sampler.c
@@ -487,6 +487,8 @@ gegl_buffer_sample (GeglBuffer       *buffer,
     return;
   }*/
 
+  static GMutex mutex = {0,};
+
   if (!format)
     format = buffer->soft_format;
 
@@ -496,6 +498,7 @@ gegl_buffer_sample (GeglBuffer       *buffer,
     gegl_buffer_cl_cache_flush (buffer, &rect);
   }
 
+  g_mutex_lock (&mutex);
 
   /* unset the cached sampler if it dosn't match the needs */
   if (buffer->sampler != NULL &&
@@ -522,6 +525,7 @@ gegl_buffer_sample (GeglBuffer       *buffer,
     }
 
   buffer->sampler->get(buffer->sampler, x, y, scale, dest, repeat_mode);
+  g_mutex_unlock (&mutex);
 }
 
 GeglSampler *