Prune unused nodes from trie

native/jni/external/systemproperties/include/_system_properties.h

@@ -109,7 +109,7 @@ int __system_property_add(const char* __name, unsigned int __name_length, const
 **
 ** Returns 0 on success, -1 if the property area is full.
 */
-int __system_property_delete(const char *__name);
+int __system_property_delete(const char *__name, bool __trim_node);
 
 /* Update the value of a system property returned by
 ** __system_property_find.  Can only be done by a single process

native/jni/external/systemproperties/include/system_properties/prop_area.h

@@ -110,7 +110,7 @@ class prop_area {
 
   const prop_info* find(const char* name);
   bool add(const char* name, unsigned int namelen, const char* value, unsigned int valuelen);
-  bool rm(const char *name);
+  bool rm(const char *name, bool trim_node);
 
   bool foreach (void (*propfn)(const prop_info* pi, void* cookie), void* cookie);
 
@@ -140,6 +140,9 @@ class prop_area {
   /* resetprop new: traverse through the trie and find the node */
   prop_bt *find_prop_bt(prop_bt *const bt, const char* name, bool alloc_if_needed);
 
+  /* resetprop new: trim unneeded nodes from trie */
+  bool prune_node(prop_bt *const node);
+
   prop_bt* find_prop_bt(prop_bt* const bt, const char* name, uint32_t namelen, bool alloc_if_needed);
 
   const prop_info* find_property(prop_bt* const trie, const char* name, uint32_t namelen,

native/jni/external/systemproperties/include/system_properties/system_properties.h

@@ -67,7 +67,7 @@ class SystemProperties {
   int Get(const char* name, char* value);
   int Update(prop_info* pi, const char* value, unsigned int len);
   int Add(const char* name, unsigned int namelen, const char* value, unsigned int valuelen);
-  int Delete(const char *name);
+  int Delete(const char *name, bool trim_node);
   uint32_t Serial(const prop_info* pi);
   uint32_t WaitAny(uint32_t old_serial);
   bool Wait(const prop_info* pi, uint32_t old_serial, uint32_t* new_serial_ptr,

native/jni/external/systemproperties/prop_area.cpp

@@ -380,7 +380,40 @@ bool prop_area::add(const char* name, unsigned int namelen, const char* value,
   return find_property(root_node(), name, namelen, value, valuelen, true);
 }
 
-bool prop_area::rm(const char *name) {
+bool prop_area::prune_node(prop_bt * const node) {
+  bool is_leaf = true;
+  if (atomic_load_explicit(&node->children, memory_order_relaxed) != 0) {
+    if (prune_node(to_prop_bt(&node->children))) {
+      atomic_store_explicit(&node->children, 0, memory_order_release);
+    } else {
+      is_leaf = false;
+    }
+  }
+  if (atomic_load_explicit(&node->left, memory_order_relaxed) != 0) {
+    if (prune_node(to_prop_bt(&node->left))) {
+      atomic_store_explicit(&node->left, 0, memory_order_release);
+    } else {
+      is_leaf = false;
+    }
+  }
+  if (atomic_load_explicit(&node->right, memory_order_relaxed) != 0) {
+    if (prune_node(to_prop_bt(&node->right))) {
+      atomic_store_explicit(&node->right, 0, memory_order_release);
+    } else {
+      is_leaf = false;
+    }
+  }
+
+  if (is_leaf && atomic_load_explicit(&node->prop, memory_order_relaxed) == 0) {
+    // Wipe out this node
+    memset(node->name, 0, node->namelen);
+    memset(node, 0, sizeof(*node));
+    return true;
+  }
+  return false;
+}
+
+bool prop_area::rm(const char *name, bool trim_node) {
   prop_bt *node = find_prop_bt(root_node(), name, false);
   if (!node)
     return false;
@@ -392,19 +425,22 @@ bool prop_area::rm(const char *name) {
   }
 
   // De-reference the existing property ASAP
-  uint_least32_t new_offset = 0;
-  atomic_store_explicit(&node->prop, new_offset, memory_order_release);
+  atomic_store_explicit(&node->prop, 0, memory_order_release);
 
   if (info) {
-    // Directly wipe out the old info
+    // Wipe out the old info
     if (info->is_long()) {
       char *value = const_cast<char*>(info->long_value());
-      auto len = strlen(value);
-      memset(value, 0, len);
+      memset(value, 0, strlen(value));
     }
+    memset(info->name, 0, strlen(info->name));
     memset(info, 0, sizeof(*info));
   }
 
+  if (trim_node) {
+    prune_node(root_node());
+  }
+
   return true;
 }
 

native/jni/external/systemproperties/system_properties.cpp

@@ -295,7 +295,7 @@ int SystemProperties::Add(const char* name, unsigned int namelen, const char* va
   return 0;
 }
 
-int SystemProperties::Delete(const char *name) {
+int SystemProperties::Delete(const char *name, bool trim_node) {
   if (!initialized_) {
     return -1;
   }
@@ -311,7 +311,7 @@ int SystemProperties::Delete(const char *name) {
     return -1;
   }
 
-  bool ret = pa->rm(name);
+  bool ret = pa->rm(name, trim_node);
   if (!ret) {
     return -1;
   }

native/jni/external/systemproperties/system_property_api.cpp

@@ -100,8 +100,8 @@ int __system_property_add(const char* name, unsigned int namelen, const char* va
 }
 
 __BIONIC_WEAK_FOR_NATIVE_BRIDGE
-int __system_property_delete(const char* name) {
-  return system_properties.Delete(name);
+int __system_property_delete(const char *name, bool trim_node) {
+  return system_properties.Delete(name, trim_node);
 }
 
 __BIONIC_WEAK_FOR_NATIVE_BRIDGE

native/jni/resetprop/resetprop.cpp

@@ -176,7 +176,7 @@ struct resetprop : public sysprop {
         // Always delete existing read-only properties, because they could be
         // long properties and cannot directly go through __system_property_update
         if (pi != nullptr && str_starts(name, "ro.")) {
-            delprop(name, false);
+            __system_property_delete(name, false /* Do NOT trim node */);
             pi = nullptr;
         }
 
@@ -228,7 +228,7 @@ struct resetprop : public sysprop {
             return 1;
         LOGD("resetprop: delete prop [%s]\n", name);
 
-        int ret = __system_property_delete(name);
+        int ret = __system_property_delete(name, true);
         if (persist && str_starts(name, "persist.")) {
             if (persist_deleteprop(name))
                 ret = 0;