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
diff --git a/init/README.md b/init/README.md
index cef0dbc..c76a33b 100644
--- a/init/README.md
+++ b/init/README.md
@@ -298,7 +298,8 @@
> Fork and execute command with the given arguments. The command starts
after "--" so that an optional security context, user, and supplementary
groups can be provided. No other commands will be run until this one
- finishes. _seclabel_ can be a - to denote default.
+ finishes. _seclabel_ can be a - to denote default. Properties are expanded
+ within _argument_.
`export <name> <value>`
> Set the environment variable _name_ equal to _value_ in the
@@ -412,6 +413,11 @@
or the timeout has been reached. If timeout is not specified it
currently defaults to five seconds.
+`wait_for_prop <name> <value>`
+> Wait for system property _name_ to be _value_. Properties are expanded
+ within _value_. If property _name_ is already set to _value_, continue
+ immediately.
+
`write <path> <content>`
> Open the file at _path_ and write a string to it with write(2).
If the file does not exist, it will be created. If it does exist,
diff --git a/init/builtins.cpp b/init/builtins.cpp
index 1186e9d..965a81f 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -1003,6 +1003,29 @@
return -1;
}
+static int do_wait_for_prop(const std::vector<std::string>& args) {
+ const char* name = args[1].c_str();
+ const char* value = args[2].c_str();
+ size_t value_len = strlen(value);
+
+ if (!is_legal_property_name(name)) {
+ LOG(ERROR) << "do_wait_for_prop(\"" << name << "\", \"" << value
+ << "\") failed: bad name";
+ return -1;
+ }
+ if (value_len >= PROP_VALUE_MAX) {
+ LOG(ERROR) << "do_wait_for_prop(\"" << name << "\", \"" << value
+ << "\") failed: value too long";
+ return -1;
+ }
+ if (!wait_property(name, value)) {
+ LOG(ERROR) << "do_wait_for_prop(\"" << name << "\", \"" << value
+ << "\") failed: init already in waiting";
+ return -1;
+ }
+ return 0;
+}
+
/*
* Callback to make a directory from the ext4 code
*/
@@ -1074,6 +1097,7 @@
{"verity_load_state", {0, 0, do_verity_load_state}},
{"verity_update_state", {0, 0, do_verity_update_state}},
{"wait", {1, 2, do_wait}},
+ {"wait_for_prop", {2, 2, do_wait_for_prop}},
{"write", {2, 2, do_write}},
};
return builtin_functions;
diff --git a/init/init.cpp b/init/init.cpp
index 850a904..9322eb2 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -87,6 +87,10 @@
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 @@
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 @@
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();
}
diff --git a/init/init.h b/init/init.h
index cfb3139..4e4da32 100644
--- a/init/init.h
+++ b/init/init.h
@@ -36,4 +36,6 @@
int add_environment(const char* key, const char* val);
+bool wait_property(const char *name, const char *value);
+
#endif /* _INIT_INIT_H */