From e94fffbacd4fd9ed25cc96d60ea98167131586a6 Mon Sep 17 00:00:00 2001
From: David Anderson <dvander@google.com>
Date: Tue, 27 Jul 2021 18:58:42 -0700
Subject: [PATCH] snapuserd: Improve EnsureSnapuserdConnected logic.

This uses a property to communicate when snapuserd is ready to accept
connections, to eliminate some non-determinism from the connect loop.

Bug: 193833730
Test: update_engine connects to snapuserd
Change-Id: I2fc0063486c3df542db1e60d12564a5bc1581a37
---
 fs_mgr/libsnapshot/snapuserd/snapuserd.rc         |  3 +++
 fs_mgr/libsnapshot/snapuserd/snapuserd_client.cpp | 14 ++++++++------
 fs_mgr/libsnapshot/snapuserd/snapuserd_server.cpp |  8 ++++++++
 3 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/fs_mgr/libsnapshot/snapuserd/snapuserd.rc b/fs_mgr/libsnapshot/snapuserd/snapuserd.rc
index 02fda8d3d..275009603 100644
--- a/fs_mgr/libsnapshot/snapuserd/snapuserd.rc
+++ b/fs_mgr/libsnapshot/snapuserd/snapuserd.rc
@@ -14,3 +14,6 @@ service snapuserd_proxy /system/bin/snapuserd -socket-handoff
     user root
     group root system
     seclabel u:r:snapuserd:s0
+
+on property:init.svc.snapuserd=stopped
+    setprop snapuserd.ready false
diff --git a/fs_mgr/libsnapshot/snapuserd/snapuserd_client.cpp b/fs_mgr/libsnapshot/snapuserd/snapuserd_client.cpp
index 81e922845..1ea05a3b0 100644
--- a/fs_mgr/libsnapshot/snapuserd/snapuserd_client.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/snapuserd_client.cpp
@@ -42,13 +42,15 @@ using namespace std::chrono_literals;
 using android::base::unique_fd;
 
 bool EnsureSnapuserdStarted() {
-    if (android::base::GetProperty("init.svc.snapuserd", "") == "running") {
-        return true;
+    if (android::base::GetProperty("init.svc.snapuserd", "") != "running") {
+        android::base::SetProperty("ctl.start", "snapuserd");
+        if (!android::base::WaitForProperty("init.svc.snapuserd", "running", 10s)) {
+            LOG(ERROR) << "Timed out waiting for snapuserd to start.";
+            return false;
+        }
     }
-
-    android::base::SetProperty("ctl.start", "snapuserd");
-    if (!android::base::WaitForProperty("init.svc.snapuserd", "running", 10s)) {
-        LOG(ERROR) << "Timed out waiting for snapuserd to start.";
+    if (!android::base::WaitForProperty("snapuserd.ready", "true", 10s)) {
+        LOG(ERROR) << "Timed out waiting for snapuserd to be ready.";
         return false;
     }
     return true;
diff --git a/fs_mgr/libsnapshot/snapuserd/snapuserd_server.cpp b/fs_mgr/libsnapshot/snapuserd/snapuserd_server.cpp
index a29b19b5a..672c13c5f 100644
--- a/fs_mgr/libsnapshot/snapuserd/snapuserd_server.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/snapuserd_server.cpp
@@ -291,6 +291,14 @@ bool SnapuserdServer::StartWithSocket(bool start_listening) {
 
     AddWatchedFd(sockfd_, POLLIN);
 
+    // If started in first-stage init, the property service won't be online.
+    if (access("/dev/socket/property_service", F_OK) == 0) {
+        if (!android::base::SetProperty("snapuserd.ready", "true")) {
+            LOG(ERROR) << "Failed to set snapuserd.ready property";
+            return false;
+        }
+    }
+
     LOG(DEBUG) << "Snapuserd server now accepting connections";
     return true;
 }