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Commit 132ac31b authored by Wei Wang's avatar Wei Wang
Browse files

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
parent afe25958

init/README.md

+7 −1
Original line number Diff line number Diff line
@@ -298,7 +298,8 @@ Commands 
> 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 @@ Commands 
  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,

init/builtins.cpp

+24 −0
Original line number Diff line number Diff line
@@ -1003,6 +1003,29 @@ static int do_wait(const std::vector<std::string>& args) { 
    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 @@ BuiltinFunctionMap::Map& BuiltinFunctionMap::map() const { 
        {"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;

init/init.cpp

+29 −1
Original line number Diff line number Diff line
@@ -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();

        }

init/init.h

+2 −0
Original line number Diff line number Diff line
@@ -36,4 +36,6 @@ void register_epoll_handler(int fd, void (*fn)()); 


int add_environment(const char* key, const char* val);



bool wait_property(const char *name, const char *value);



#endif  /* _INIT_INIT_H */