From f7025200449c8208ca6136e5a23340b3d28c8516 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Wed, 5 Jun 2019 15:06:16 -0700
Subject: [PATCH] ircd: Add infrastructure to handle continuation notification
 after suspending.

---
 construct/README.md  |  7 +++++++
 construct/signals.cc | 47 ++++++++++++++++++++++++++++++--------------
 include/ircd/ircd.h  |  4 +++-
 ircd/ircd.cc         | 38 +++++++++++++++++++++++++++++++++++
 4 files changed, 80 insertions(+), 16 deletions(-)

diff --git a/construct/README.md b/construct/README.md
index 48ac7fc03..fd45dd351 100644
--- a/construct/README.md
+++ b/construct/README.md
@@ -46,3 +46,10 @@ server configuration et al is moved to `SIGUSR1`.
 
 This signal commands the server to reload and refresh various aspects of its
 configuration and running state.
+
+##### SIGCONT
+
+This signal is used to notify the server that execution has resumed after an
+unexpected gap. We call `ircd::cont()` after receiving this signal. Examples
+for when the server benefits from calling `ircd::cont()` are: after a previous
+stop signal, debugging, or ACPI suspend and resume, etc.
diff --git a/construct/signals.cc b/construct/signals.cc
index 622357546..dfa3c3cc0 100644
--- a/construct/signals.cc
+++ b/construct/signals.cc
@@ -18,6 +18,7 @@ namespace construct
 {
 	namespace ph = std::placeholders;
 
+	static void handle_cont();
 	static void handle_usr1();
 	static void handle_quit();
 	static void handle_interrupt();
@@ -40,6 +41,7 @@ construct::signals::signals(boost::asio::io_context &ios)
 	signal_set->add(SIGQUIT);
 	signal_set->add(SIGTERM);
 	signal_set->add(SIGUSR1);
+	signal_set->add(SIGCONT);
 	set_handle();
 }
 
@@ -115,11 +117,12 @@ construct::handle_signal(const int &signum)
 {
 	switch(signum)
 	{
-		case SIGINT:   return handle_interrupt();
 		case SIGHUP:   return handle_hangup();
+		case SIGINT:   return handle_interrupt();
 		case SIGQUIT:  return handle_quit();
 		case SIGTERM:  return handle_quit();
 		case SIGUSR1:  return handle_usr1();
+		case SIGCONT:  return handle_cont();
 		default:       break;
 	}
 
@@ -129,20 +132,6 @@ construct::handle_signal(const int &signum)
 	};
 }
 
-void
-construct::handle_quit()
-try
-{
-	ircd::quit();
-}
-catch(const std::exception &e)
-{
-	ircd::log::error
-	{
-		"SIGQUIT handler: %s", e.what()
-	};
-}
-
 void
 construct::handle_hangup()
 try
@@ -181,6 +170,20 @@ catch(const std::exception &e)
 	};
 }
 
+void
+construct::handle_quit()
+try
+{
+	ircd::quit();
+}
+catch(const std::exception &e)
+{
+	ircd::log::error
+	{
+		"SIGQUIT handler: %s", e.what()
+	};
+}
+
 void
 construct::handle_usr1()
 try
@@ -219,3 +222,17 @@ catch(const std::exception &e)
 		"SIGUSR1 handler: %s", e.what()
 	};
 }
+
+void
+construct::handle_cont()
+try
+{
+	ircd::cont();
+}
+catch(const std::exception &e)
+{
+	ircd::log::error
+	{
+		"SIGCONT handler: %s", e.what()
+	};
+}
diff --git a/include/ircd/ircd.h b/include/ircd/ircd.h
index 2b8c205a7..4fc863aef 100644
--- a/include/ircd/ircd.h
+++ b/include/ircd/ircd.h
@@ -69,8 +69,10 @@
 namespace ircd
 {
 	seconds uptime();
-	void init(boost::asio::io_context &ios, const string_view &origin, const string_view &hostname);
+
+	void cont() noexcept;
 	bool quit() noexcept;
+	void init(boost::asio::io_context &ios, const string_view &origin, const string_view &hostname);
 
 	extern conf::item<bool> restart;
 	extern conf::item<bool> debugmode;
diff --git a/ircd/ircd.cc b/ircd/ircd.cc
index 48251df36..1c461bf16 100644
--- a/ircd/ircd.cc
+++ b/ircd/ircd.cc
@@ -201,6 +201,44 @@ noexcept
 	return false;
 }
 
+/// Notifies IRCd that execution is being resumed after a significant gap.
+/// Basically this is connected to a SIGCONT handler and beneficial after
+/// user stops, debugging and ACPI suspensions, etc. It is not required at
+/// this time, but its connection is advised for best behavior.
+void
+ircd::cont()
+noexcept
+{
+	log::debug
+	{
+		"IRCd cont requested from runlevel:%s ctx:%p main_context:%p",
+		reflect(run::level),
+		(const void *)ctx::current,
+		(const void *)main_context
+	};
+
+	switch(run::level)
+	{
+		case run::level::HALT:
+		case run::level::READY:
+		case run::level::FAULT:
+			return;
+
+		case run::level::START:
+		case run::level::QUIT:
+			return;
+
+		case run::level::RUN:
+			break;
+	}
+
+	log::notice
+	{
+		"IRCd resuming service in runlevel:%s.",
+		reflect(run::level),
+	};
+}
+
 /// Main context; Main program. Do not call this function directly.
 ///
 /// This function manages the lifetime for all resources and subsystems