unix/SignalHandlers: shut down if parent process dies in --no-daemon mode

By default, if the parent of a process dies, the process gets SIGHUP and is supposed to shut down. This however doesn't work for MPD, because MPD redefines SIGHUP with a different meaning (like most daemons do). To work around this, we configure the kernel to send SIGTERM instead of SIGHUP. Closes https://github.com/MusicPlayerDaemon/MPD/issues/1706

unix/SignalHandlers: shut down if parent process dies in --no-daemon mode
a0f6932e · Max Kellermann · 6e700dab · a0f6932e · a0f6932e · a0f6932e
Commit a0f6932e authored Mar 06, 2023 by Max Kellermann
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Showing with 22 additions and 5 deletions

NEWS NEWS +2 -0

Main.cxx src/Main.cxx +4 -1

SignalHandlers.cxx src/unix/SignalHandlers.cxx +13 -1

SignalHandlers.hxx src/unix/SignalHandlers.hxx +3 -3

No files found.
--- a/NEWS
+++ b/NEWS
@@ -3,6 +3,8 @@ ver 0.23.13 (not yet released)
  - curl: fix busy loop after connection failed
 * output
  - pipewire: fix corruption bug due to missing lock
+* Linux
+  - shut down if parent process dies in --no-daemon mode

 ver 0.23.12 (2023/01/17)
 * input

--- a/src/Main.cxx
+++ b/src/Main.cxx
@@ -482,7 +482,10 @@ MainConfigured(const CommandLineOptions &options,
 #ifndef ANDROID
 	setup_log_output();

-	const ScopeSignalHandlersInit signal_handlers_init(instance);
+	const ScopeSignalHandlersInit signal_handlers_init{
+		instance,
+		options.daemon,
+	};
 #endif

 	instance.io_thread.Start();

--- a/src/unix/SignalHandlers.cxx
+++ b/src/unix/SignalHandlers.cxx
@@ -30,6 +30,10 @@

 #include <csignal>

+#ifdef __linux__
+#include <sys/prctl.h>
+#endif
+
 static constexpr Domain signal_handlers_domain("signal_handlers");

 static void
@@ -60,7 +64,7 @@ handle_reload_event(void *ctx) noexcept
 #endif

 void
-SignalHandlersInit(Instance &instance)
+SignalHandlersInit(Instance &instance, bool daemon)
 {
 	auto &loop = instance.event_loop;

@@ -79,6 +83,14 @@ SignalHandlersInit(Instance &instance)

 	SignalMonitorRegister(SIGHUP, {&instance, handle_reload_event});
 #endif
+
+	if (!daemon) {
+#ifdef __linux__
+		/* if MPD was not daemonized, shut it down when the
+		   parent process dies */
+		prctl(PR_SET_PDEATHSIG, SIGTERM);
+#endif
+	}
 }

 void

--- a/src/unix/SignalHandlers.hxx
+++ b/src/unix/SignalHandlers.hxx
@@ -23,15 +23,15 @@
 struct Instance;

 void
-SignalHandlersInit(Instance &instance);
+SignalHandlersInit(Instance &instance, bool daemon);

 void
 SignalHandlersFinish() noexcept;

 class ScopeSignalHandlersInit {
 public:
-	ScopeSignalHandlersInit(Instance &instance) {
-		SignalHandlersInit(instance);
+	ScopeSignalHandlersInit(Instance &instance, bool daemon) {
+		SignalHandlersInit(instance, daemon);
 	}

 	~ScopeSignalHandlersInit() noexcept {