init: add exec_start command

Exec services may also want to set other service flags such as
priority.  Instead of expanding the exec syntax to handle this, create
a new command, exec_start, that will treat an existing service
definition as an exec service.  The new exec_start command will start
the service then halt init from executing further commands until the
service has exited.

This change additionally encapsulates the waiting_for_exec logic into
ServiceManager and removes the ambiguous 'bool' return value from
Reap() which previously indicated if a Reaped service was an exec
service or not.

Bug: 36511808
Bug: 36102163
Test: Bullhead boots, services run with exec_start as they do exec.

Change-Id: I44f775cf1c1dd81d5c715f44fdc150c651a2c80a

1 files changed, 8 insertions, 13 deletions

diff --git a/init/builtins.cpp b/init/builtins.cpp
index 32e9ef642..c860e4001 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -161,19 +161,11 @@ static int do_enable(const std::vector<std::string>& args) {
 }
 
 static int do_exec(const std::vector<std::string>& args) {
-    Service* svc = ServiceManager::GetInstance().MakeExecOneshotService(args);
-    if (!svc) {
-        return -1;
-    }
-    if (!start_waiting_for_exec()) {
-        return -1;
-    }
-    if (!svc->Start()) {
-        stop_waiting_for_exec();
-        ServiceManager::GetInstance().RemoveService(*svc);
-        return -1;
-    }
-    return 0;
+    return ServiceManager::GetInstance().Exec(args) ? 0 : -1;
+}
+
+static int do_exec_start(const std::vector<std::string>& args) {
+    return ServiceManager::GetInstance().ExecStart(args[1]) ? 0 : -1;
 }
 
 static int do_export(const std::vector<std::string>& args) {
@@ -892,6 +884,7 @@ static int do_init_user0(const std::vector<std::string>& args) {
 
 BuiltinFunctionMap::Map& BuiltinFunctionMap::map() const {
     constexpr std::size_t kMax = std::numeric_limits<std::size_t>::max();
+    // clang-format off
     static const Map builtin_functions = {
         {"bootchart",               {1,     1,    do_bootchart}},
         {"chmod",                   {2,     2,    do_chmod}},
@@ -903,6 +896,7 @@ BuiltinFunctionMap::Map& BuiltinFunctionMap::map() const {
         {"domainname",              {1,     1,    do_domainname}},
         {"enable",                  {1,     1,    do_enable}},
         {"exec",                    {1,     kMax, do_exec}},
+        {"exec_start",              {1,     1,    do_exec_start}},
         {"export",                  {2,     2,    do_export}},
         {"hostname",                {1,     1,    do_hostname}},
         {"ifup",                    {1,     1,    do_ifup}},
@@ -936,5 +930,6 @@ BuiltinFunctionMap::Map& BuiltinFunctionMap::map() const {
         {"wait_for_prop",           {2,     2,    do_wait_for_prop}},
         {"write",                   {2,     2,    do_write}},
     };
+    // clang-format on
     return builtin_functions;
 }