init: Handle properties in the background of calling fs_mgr

It's been a long standing problem that init calls fs_mgr functions
synchronously and therefore stops handling properties, which causes
deadlocks if either fs_mgr, or vdc, or vold attempt to set
properties.

Previous work, b/21904461, shows that there is a large performance
penalty for adding any amount of locking to properties, so moving
property service into its own thread generically is not a viable
option.  However, we can be sure that init is not setting properties
while the fs_mgr functions are running, so we can poll the property
socket in a thread while we call these functions.

The other alternative would have been to separate the fs_mgr functions
into smaller pieces and revisit the main init loop between each
piece.  Unfortunately, this would be difficult, since
fs_mgr_mount_all() calls out to different processes via logwrapper,
which synchronously polls on a logging FD from the child, among other
complexities that would make this strategy much more difficult than it
would be worth.

Bug: 21904461
Test: device boots, including when setting property in
      fs_mgr_mount_all()

Change-Id: Ib0b7123024035884f9d90f9b489c1e2f5a2e1707

1 files changed, 21 insertions, 6 deletions

diff --git a/init/builtins.cpp b/init/builtins.cpp
index 44cac4b7d..d9b1b8530 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -588,7 +588,12 @@ static Result<void> do_mount_all(const BuiltinArguments& args) {
     if (!ReadFstabFromFile(fstab_file, &fstab)) {
         return Error() << "Could not read fstab";
     }
-    auto mount_fstab_return_code = fs_mgr_mount_all(&fstab, mount_mode);
+
+    auto mount_fstab_return_code =
+            CallFunctionAndHandleProperties(fs_mgr_mount_all, &fstab, mount_mode);
+    if (!mount_fstab_return_code) {
+        return Error() << "Could not call fs_mgr_mount_all(): " << mount_fstab_return_code.error();
+    }
     property_set(prop_name, std::to_string(t.duration().count()));
 
     if (import_rc && SelinuxGetVendorAndroidVersion() <= __ANDROID_API_Q__) {
@@ -599,7 +604,7 @@ static Result<void> do_mount_all(const BuiltinArguments& args) {
     if (queue_event) {
         /* queue_fs_event will queue event based on mount_fstab return code
          * and return processed return code*/
-        auto queue_fs_result = queue_fs_event(mount_fstab_return_code);
+        auto queue_fs_result = queue_fs_event(*mount_fstab_return_code);
         if (!queue_fs_result) {
             return Error() << "queue_fs_event() failed: " << queue_fs_result.error();
         }
@@ -615,8 +620,13 @@ static Result<void> do_umount_all(const BuiltinArguments& args) {
         return Error() << "Could not read fstab";
     }
 
-    if (auto result = fs_mgr_umount_all(&fstab); result != 0) {
-        return Error() << "umount_fstab() failed " << result;
+    auto result = CallFunctionAndHandleProperties(fs_mgr_umount_all, &fstab);
+    if (!result) {
+        return Error() << "Could not call fs_mgr_mount_all() " << result.error();
+    }
+
+    if (*result != 0) {
+        return Error() << "fs_mgr_mount_all() failed: " << *result;
     }
     return {};
 }
@@ -627,8 +637,13 @@ static Result<void> do_swapon_all(const BuiltinArguments& args) {
         return Error() << "Could not read fstab '" << args[1] << "'";
     }
 
-    if (!fs_mgr_swapon_all(fstab)) {
-        return Error() << "fs_mgr_swapon_all() failed";
+    auto result = CallFunctionAndHandleProperties(fs_mgr_swapon_all, fstab);
+    if (!result) {
+        return Error() << "Could not call fs_mgr_swapon_all() " << result.error();
+    }
+
+    if (*result == 0) {
+        return Error() << "fs_mgr_swapon_all() failed.";
     }
 
     return {};