libsysprof: add rwlock for symbol cache

This is necessary so we can start looking at threading symbolizers.

src/libsysprof/sysprof-symbol-cache.c

@@ -42,6 +42,7 @@ struct _SysprofSymbolCacheNode
 struct _SysprofSymbolCache
 {
   GObject parent_instance;
+  GRWLock rwlock;
   RB_HEAD(sysprof_symbol_cache, _SysprofSymbolCacheNode) head;
 };
 
@@ -104,6 +105,8 @@ sysprof_symbol_cache_finalize (GObject *object)
   if (node != NULL)
     sysprof_symbol_cache_node_free (node);
 
+  g_rw_lock_clear (&self->rwlock);
+
   G_OBJECT_CLASS (sysprof_symbol_cache_parent_class)->finalize (object);
 }
 
@@ -118,6 +121,7 @@ sysprof_symbol_cache_class_init (SysprofSymbolCacheClass *klass)
 static void
 sysprof_symbol_cache_init (SysprofSymbolCache *self)
 {
+  g_rw_lock_init (&self->rwlock);
   RB_INIT (&self->head);
 }
 
@@ -154,11 +158,14 @@ sysprof_symbol_cache_take (SysprofSymbolCache *self,
   node->high = symbol->end_address-1;
   node->max = node->high;
 
+  g_rw_lock_writer_lock (&self->rwlock);
+
   /* If there is a collision, then the node is returned. Otherwise
    * if the node was inserted, NULL is returned.
    */
   if ((ret = RB_INSERT(sysprof_symbol_cache, &self->head, node)))
     {
+      g_rw_lock_writer_unlock (&self->rwlock);
       sysprof_symbol_cache_node_free (node);
       return;
     }
@@ -172,6 +179,8 @@ sysprof_symbol_cache_take (SysprofSymbolCache *self,
       node = parent;
       parent = RB_PARENT(parent, link);
     }
+
+  g_rw_lock_writer_unlock (&self->rwlock);
 }
 
 SysprofSymbol *
@@ -185,6 +194,8 @@ sysprof_symbol_cache_lookup (SysprofSymbolCache *self,
   if (address == 0)
     return NULL;
 
+  g_rw_lock_reader_lock (&self->rwlock);
+
   node = RB_ROOT(&self->head);
 
   /* The root node contains our calculated max as augmented in RBTree.
@@ -192,7 +203,10 @@ sysprof_symbol_cache_lookup (SysprofSymbolCache *self,
    * in O(1) without having to add a branch to the while loop below.
    */
   if (node == NULL || node->max < address)
-    return NULL;
+    {
+      g_rw_lock_reader_unlock (&self->rwlock);
+      return NULL;
+    }
 
   while (node != NULL)
     {
@@ -202,7 +216,10 @@ sysprof_symbol_cache_lookup (SysprofSymbolCache *self,
                 node->max >= RB_RIGHT(node, link)->max);
 
       if (address >= node->low && address <= node->high)
-        return node->symbol;
+        {
+          g_rw_lock_reader_unlock (&self->rwlock);
+          return node->symbol;
+        }
 
       if (RB_LEFT(node, link) && RB_LEFT(node, link)->max >= address)
         node = RB_LEFT(node, link);
@@ -210,6 +227,8 @@ sysprof_symbol_cache_lookup (SysprofSymbolCache *self,
         node = RB_RIGHT(node, link);
     }
 
+  g_rw_lock_reader_unlock (&self->rwlock);
+
   return NULL;
 }