From 69dc3ccd8952a109bb83dfdc1a57590b8eed8fe0 Mon Sep 17 00:00:00 2001
From: Krzysztof Jackiewicz <k.jackiewicz@samsung.com>
Date: Thu, 1 Feb 2018 15:02:34 +0100
Subject: [PATCH] Wait for unit to stop instead of sleeping

Oded asks systemd to stop certain units before unmounting /opt/usr but it
doesn't wait for confirmation. Instead it performs sleep(1).

This commit implements a mechanism that waits for unit stop confirmation from
systemd.

Change-Id: I50d4ca8d234221b8af457852548a5d9230f4ec2b
---
 server/internal-encryption.cpp | 98 ++++++++++++++++++++++++++++++++--
 1 file changed, 94 insertions(+), 4 deletions(-)

diff --git a/server/internal-encryption.cpp b/server/internal-encryption.cpp
index 7c9051e..32f1463 100644
--- a/server/internal-encryption.cpp
+++ b/server/internal-encryption.cpp
@@ -16,6 +16,9 @@
 #include <set>
 #include <algorithm>
 #include <memory>
+#include <mutex>
+#include <condition_variable>
+#include <list>
 
 #include <fcntl.h>
 #include <signal.h>
@@ -60,6 +63,83 @@ const std::vector<std::string> wipeCommand = {
     "com.samsung.factoryreset.start.setting"
 };
 
+
+// watches systemd jobs
+class JobWatch {
+public:
+	explicit JobWatch(dbus::Connection& systemDBus);
+	~JobWatch();
+
+	bool waitForJob(const std::string& job);
+
+private:
+	void jobRemoved(const dbus::Variant& parameters);
+
+	struct Job {
+		Job(uint32_t id,
+			const std::string& job,
+			const std::string& unit,
+			const std::string& result) : id(id), job(job), unit(unit), result(result) {}
+		uint32_t id;
+		std::string job;
+		std::string unit;
+		std::string result;
+	};
+
+	dbus::Connection::SubscriptionId id;
+	dbus::Connection& systemDBus;
+	std::list<Job> removedJobs;
+	std::mutex jobsMutex;
+	std::condition_variable jobsCv;
+};
+
+JobWatch::JobWatch(dbus::Connection& systemDBus) : systemDBus(systemDBus) {
+	auto callback = [this](dbus::Variant parameters) {
+		this->jobRemoved(parameters);
+	};
+
+	id = systemDBus.subscribeSignal("",
+									"/org/freedesktop/systemd1",
+									"org.freedesktop.systemd1.Manager",
+									"JobRemoved",
+									callback);
+}
+
+JobWatch::~JobWatch() {
+	systemDBus.unsubscribeSignal(id);
+}
+
+bool JobWatch::waitForJob(const std::string& job) {
+	while(true) {
+		std::unique_lock<std::mutex> lock(jobsMutex);
+		jobsCv.wait(lock, [this]{ return !removedJobs.empty(); });
+
+		while(!removedJobs.empty()) {
+			bool match = (removedJobs.front().job == job);
+			bool done = (removedJobs.front().result == "done");
+			removedJobs.pop_front();
+			if (match)
+				return done;
+		}
+	};
+}
+
+void JobWatch::jobRemoved(const dbus::Variant& parameters)
+{
+	uint32_t id;
+	const char* job;
+	const char* unit;
+	const char* result;
+	parameters.get("(uoss)", &id, &job, &unit, &result);
+	INFO(SINK, "id:" + std::to_string(id) + " job:" + job + " unit:" + unit + " result:" + result);
+
+	{
+		std::lock_guard<std::mutex> guard(jobsMutex);
+		removedJobs.emplace_back(id, job, unit, result);
+	}
+	jobsCv.notify_one();
+}
+
 void stopKnownSystemdUnits()
 {
 	std::vector<std::string> knownSystemdUnits;
@@ -98,16 +178,20 @@ void stopKnownSystemdUnits()
 		}
 	}
 
+	JobWatch watch(systemDBus);
+
 	for (const std::string& unit : knownSystemdUnits) {
 		INFO(SINK, "Stopping unit: " + unit);
+		const char* job = NULL;
 		systemDBus.methodcall("org.freedesktop.systemd1",
 								"/org/freedesktop/systemd1",
 								"org.freedesktop.systemd1.Manager",
 								"StopUnit",
-								-1, "", "(ss)", unit.c_str(), "flush");
+								-1, "(o)", "(ss)", unit.c_str(), "flush").get("(o)", &job);
+		INFO(SINK, "Waiting for job: " + std::string(job));
+		if (!watch.waitForJob(job))
+			throw runtime::Exception("Stopping unit: " + unit + " failed");
 	}
-
-	sleep(1); // TODO wait for confirmation from systemd instead
 }
 
 void stopDependedSystemdUnits()
@@ -131,13 +215,19 @@ void stopDependedSystemdUnits()
 		}
 	}
 
+	JobWatch watch(systemDBus);
+
 	for (const std::string& unit : unitsToStop) {
 		INFO(SINK, "Stopping unit: " + unit);
+		const char* job = NULL;
 		systemDBus.methodcall("org.freedesktop.systemd1",
 								unit,
 								"org.freedesktop.systemd1.Unit",
 								"Stop",
-								-1, "", "(s)", "flush");
+								-1, "(o)", "(s)", "flush").get("(o)", &job);
+		INFO(SINK, "Waiting for job: " + std::string(job));
+		if (!watch.waitForJob(job))
+			throw runtime::Exception("Stopping unit: " + unit + " failed");
 	}
 }
 
-- 
2.34.1