init: add wait_for_prop builtin command

There are many use cases from vendors to exec service in background and then
use a shell scriprt to wait for the command done.

This CL is to add a wait_for_prop command to suppor those use cases.

Bug: 34746108
Test: on marlin
Change-Id: Ia81290b0928f9d375710d2daa546714f0cd65b72

1 files changed, 29 insertions, 1 deletions

diff --git a/init/init.cpp b/init/init.cpp
index 850a9046e..9322eb28e 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -87,6 +87,10 @@ bool waiting_for_exec = false;
 
 static int epoll_fd = -1;
 
+static std::unique_ptr<Timer> waiting_for_prop(nullptr);
+static std::string wait_prop_name;
+static std::string wait_prop_value;
+
 void register_epoll_handler(int fd, void (*fn)()) {
     epoll_event ev;
     ev.events = EPOLLIN;
@@ -128,10 +132,34 @@ int add_environment(const char *key, const char *val)
     return -1;
 }
 
+bool wait_property(const char *name, const char *value)
+{
+    if (waiting_for_prop) {
+        return false;
+    }
+    if (property_get(name) != value) {
+        // Current property value is not equal to expected value
+        wait_prop_name = name;
+        wait_prop_value = value;
+        waiting_for_prop.reset(new Timer());
+    } else {
+        LOG(INFO) << "wait_property(\"" << name << "\", \"" << value << "\"): already set";
+    }
+    return true;
+}
+
 void property_changed(const char *name, const char *value)
 {
     if (property_triggers_enabled)
         ActionManager::GetInstance().QueuePropertyTrigger(name, value);
+    if (waiting_for_prop) {
+        if (wait_prop_name == name && wait_prop_value == value) {
+            wait_prop_name.clear();
+            wait_prop_value.clear();
+            LOG(INFO) << "Wait for property took " << *waiting_for_prop;
+            waiting_for_prop.reset();
+        }
+    }
 }
 
 static void restart_processes()
@@ -876,7 +904,7 @@ int main(int argc, char** argv) {
     am.QueueBuiltinAction(queue_property_triggers_action, "queue_property_triggers");
 
     while (true) {
-        if (!waiting_for_exec) {
+        if (!(waiting_for_exec || waiting_for_prop)) {
             am.ExecuteOneCommand();
             restart_processes();
         }