Merge branch 'egil/erts/handle-sigterm-nicely/OTP-14085' into maint

* egil/erts/handle-sigterm-nicely/OTP-14085:
  erts: Document SIGTERM handler
  erts: Add SIGTERM signal handler

2 files changed, 59 insertions, 0 deletions

diff --git a/erts/doc/src/erl.xml b/erts/doc/src/erl.xml
index f2a55f6298..8da832ac37 100644
--- a/erts/doc/src/erl.xml
+++ b/erts/doc/src/erl.xml
@@ -1595,6 +1595,25 @@
   </section>
 
   <section>
+      <marker id="signals"></marker>
+      <title>Signals</title>
+      <p>On Unix systems, the Erlang runtime will interpret two types of signals.</p>
+      <taglist>
+          <tag><c>SIGUSR1</c></tag>
+          <item>
+              <p>A <c>SIGUSR1</c> signal forces a crash dump.</p>
+          </item>
+          <tag><c>SIGTERM</c></tag>
+          <item>
+              <p>A <c>SIGTERM</c> will produce a <c>stop</c> message to the <c>init</c> process.
+                  This is equivalent to a <c>init:stop/0</c> call.</p>
+              <p>Introduced in ERTS 8.3 (Erlang/OTP 19.3)</p>
+          </item>
+      </taglist>
+      <p>The signal <c>SIGUSR2</c> is reserved for internal usage. No other signals are handled.</p>
+  </section>
+
+  <section>
     <marker id="configuration"></marker>
     <title>Configuration</title>
     <p>The standard Erlang/OTP system can be reconfigured to change the default
diff --git a/erts/emulator/sys/unix/sys.c b/erts/emulator/sys/unix/sys.c
index 4b2edace0a..2fc802a2c6 100644
--- a/erts/emulator/sys/unix/sys.c
+++ b/erts/emulator/sys/unix/sys.c
@@ -407,6 +407,7 @@ erts_sys_pre_init(void)
 #ifdef ERTS_THR_HAVE_SIG_FUNCS
     sigemptyset(&thr_create_sigmask);
     sigaddset(&thr_create_sigmask, SIGINT);   /* block interrupt */
+    sigaddset(&thr_create_sigmask, SIGTERM);  /* block terminate signal */
     sigaddset(&thr_create_sigmask, SIGUSR1);  /* block user defined signal */
 #endif
 
@@ -655,6 +656,40 @@ static RETSIGTYPE request_break(int signum)
 #endif
 }
 
+static void stop_requested(void) {
+    Process* p = NULL;
+    Eterm msg, *hp;
+    ErtsProcLocks locks = 0;
+    ErlOffHeap *ohp;
+    Eterm id = erts_whereis_name_to_id(NULL, am_init);
+
+    if ((p = (erts_pid2proc_opt(NULL, 0, id, 0, ERTS_P2P_FLG_INC_REFC))) != NULL) {
+        ErtsMessage *msgp = erts_alloc_message_heap(p, &locks, 3, &hp, &ohp);
+
+        /* init ! {stop,stop} */
+        msg = TUPLE2(hp, am_stop, am_stop);
+        erts_queue_message(p, locks, msgp, msg, am_system);
+
+        if (locks)
+            erts_smp_proc_unlock(p, locks);
+        erts_proc_dec_refc(p);
+    }
+}
+
+#if (defined(SIG_SIGSET) || defined(SIG_SIGNAL))
+static RETSIGTYPE request_stop(void)
+#else
+static RETSIGTYPE request_stop(int signum)
+#endif
+{
+#ifdef ERTS_SMP
+    smp_sig_notify('S');
+#else
+    stop_requested();
+#endif
+}
+
+
 static ERTS_INLINE void
 sigusr1_exit(void)
 {
@@ -751,6 +786,7 @@ static RETSIGTYPE do_quit(int signum)
 /* Disable break */
 void erts_set_ignore_break(void) {
     sys_signal(SIGINT,  SIG_IGN);
+    sys_signal(SIGTERM, SIG_IGN);
     sys_signal(SIGQUIT, SIG_IGN);
     sys_signal(SIGTSTP, SIG_IGN);
 }
@@ -776,6 +812,7 @@ void erts_replace_intr(void) {
 void init_break_handler(void)
 {
    sys_signal(SIGINT, request_break);
+   sys_signal(SIGTERM, request_stop);
 #ifndef ETHR_UNUSABLE_SIGUSRX
    sys_signal(SIGUSR1, user_signal1);
 #endif /* #ifndef ETHR_UNUSABLE_SIGUSRX */
@@ -1289,6 +1326,9 @@ signal_dispatcher_thread_func(void *unused)
 	    switch (buf[i]) {
 	    case 0: /* Emulator initialized */
                 break;
+	    case 'S': /* SIGTERM */
+		stop_requested();
+		break;
 	    case 'I': /* SIGINT */
 		break_requested();
 		break;