Fix deadlock caused by two-threaded property controls

Two threaded property controls were introduced in ag/21063815 to prevent
DOS for power controls. However, this causes deadlocks, so limit the
second thread to just sys.powerctl messages.

Bug: 273785601
Test: Boots, power messages work
Ignore-AOSP-First: Security fix
Change-Id: Ie27dc3b0cd9e2d28e94f2ad398c55ee27bc35835
diff --git a/init/property_service.cpp b/init/property_service.cpp
index 2d084db..4242912 100644
--- a/init/property_service.cpp
+++ b/init/property_service.cpp
@@ -117,7 +117,6 @@
 static std::mutex accept_messages_lock;
 static std::thread property_service_thread;
 static std::thread property_service_for_system_thread;
-static std::mutex set_property_lock;
 
 static std::unique_ptr<PersistWriteThread> persist_write_thread;
 
@@ -395,32 +394,37 @@
         return {PROP_ERROR_INVALID_VALUE};
     }
 
-    auto lock = std::lock_guard{set_property_lock};
-    prop_info* pi = (prop_info*)__system_property_find(name.c_str());
-    if (pi != nullptr) {
-        // ro.* properties are actually "write-once".
-        if (StartsWith(name, "ro.")) {
-            *error = "Read-only property was already set";
-            return {PROP_ERROR_READ_ONLY_PROPERTY};
-        }
-
-        __system_property_update(pi, value.c_str(), valuelen);
+    if (name == "sys.powerctl") {
+        // No action here - NotifyPropertyChange will trigger the appropriate action, and since this
+        // can come to the second thread, we mustn't call out to the __system_property_* functions
+        // which support multiple readers but only one mutator.
     } else {
-        int rc = __system_property_add(name.c_str(), name.size(), value.c_str(), valuelen);
-        if (rc < 0) {
-            *error = "__system_property_add failed";
-            return {PROP_ERROR_SET_FAILED};
-        }
-    }
+        prop_info* pi = (prop_info*)__system_property_find(name.c_str());
+        if (pi != nullptr) {
+            // ro.* properties are actually "write-once".
+            if (StartsWith(name, "ro.")) {
+                *error = "Read-only property was already set";
+                return {PROP_ERROR_READ_ONLY_PROPERTY};
+            }
 
-    // Don't write properties to disk until after we have read all default
-    // properties to prevent them from being overwritten by default values.
-    if (socket && persistent_properties_loaded && StartsWith(name, "persist.")) {
-        if (persist_write_thread) {
-            persist_write_thread->Write(name, value, std::move(*socket));
-            return {};
+            __system_property_update(pi, value.c_str(), valuelen);
+        } else {
+            int rc = __system_property_add(name.c_str(), name.size(), value.c_str(), valuelen);
+            if (rc < 0) {
+                *error = "__system_property_add failed";
+                return {PROP_ERROR_SET_FAILED};
+            }
         }
-        WritePersistentProperty(name, value);
+
+        // Don't write properties to disk until after we have read all default
+        // properties to prevent them from being overwritten by default values.
+        if (socket && persistent_properties_loaded && StartsWith(name, "persist.")) {
+            if (persist_write_thread) {
+                persist_write_thread->Write(name, value, std::move(*socket));
+                return {};
+            }
+            WritePersistentProperty(name, value);
+        }
     }
 
     NotifyPropertyChange(name, value);