Merge pull request #114 from pks-t/pks/pdeathsignal

Add '-p' flag to get signalled  when parent dies

README.md

@@ -175,6 +175,20 @@ closely to what happens when you do ctrl-C etc. in a terminal: The
 signal is sent to the foreground process group.
 
 
+### Parent Death Signal ###
+
+Tini can set its parent death signal, which is the signal Tini should receive
+when *its* parent exits. To set the parent death signal, use the `-p` flag with
+the name of the signal Tini should receive when its parent exits:
+
+```
+tini -p SIGTERM -- ...
+```
+
+*NOTE: See [this PR discussion][12] to learn more about the parent death signal
+and use cases.*
+
+
 More
 ----
 
@@ -257,6 +271,7 @@ Contributors:
   + [David Wragg][31]
   + [Michael Crosby][32]
   + [Wyatt Preul][33]
+  + [Patrick Steinhardt][34]
 
 Special thanks to:
 
@@ -268,10 +283,12 @@ Special thanks to:
   [5]: https://docs.docker.com/engine/reference/commandline/run/
   [10]: https://github.com/krallin/tini-images
   [11]: https://github.com/krallin/tini/releases
+  [12]: https://github.com/krallin/tini/pull/114
   [20]: https://github.com/krallin/
   [30]: https://github.com/tianon
   [31]: https://github.com/dpw
   [32]: https://github.com/crosbymichael
   [33]: https://github.com/geek
+  [34]: https://github.com/pks-t
   [40]: https://github.com/danilobuerger
   [41]: https://github.com/datakurre

src/tini.c

@@ -50,17 +50,51 @@ typedef struct {
    struct sigaction* const sigttou_action_ptr;
 } signal_configuration_t;
 
+static const struct {
+   char *const name;
+   int number;
+} signal_names[] = {
+   { "SIGHUP", SIGHUP },
+   { "SIGINT", SIGINT },
+   { "SIGQUIT", SIGQUIT },
+   { "SIGILL", SIGILL },
+   { "SIGTRAP", SIGTRAP },
+   { "SIGABRT", SIGABRT },
+   { "SIGBUS", SIGBUS },
+   { "SIGFPE", SIGFPE },
+   { "SIGKILL", SIGKILL },
+   { "SIGUSR1", SIGUSR1 },
+   { "SIGSEGV", SIGSEGV },
+   { "SIGUSR2", SIGUSR2 },
+   { "SIGPIPE", SIGPIPE },
+   { "SIGALRM", SIGALRM },
+   { "SIGTERM", SIGTERM },
+   { "SIGCHLD", SIGCHLD },
+   { "SIGCONT", SIGCONT },
+   { "SIGSTOP", SIGSTOP },
+   { "SIGTSTP", SIGTSTP },
+   { "SIGTTIN", SIGTTIN },
+   { "SIGTTOU", SIGTTOU },
+   { "SIGURG", SIGURG },
+   { "SIGXCPU", SIGXCPU },
+   { "SIGXFSZ", SIGXFSZ },
+   { "SIGVTALRM", SIGVTALRM },
+   { "SIGPROF", SIGPROF },
+   { "SIGWINCH", SIGWINCH },
+   { "SIGSYS", SIGSYS },
+};
+
 static unsigned int verbosity = DEFAULT_VERBOSITY;
 
 static int32_t expect_status[(STATUS_MAX - STATUS_MIN + 1) / 32];
 
 #ifdef PR_SET_CHILD_SUBREAPER
 #define HAS_SUBREAPER 1
-#define OPT_STRING "hvwgle:s"
+#define OPT_STRING "p:hvwgle:s"
 #define SUBREAPER_ENV_VAR "TINI_SUBREAPER"
 #else
 #define HAS_SUBREAPER 0
-#define OPT_STRING "hvwgle:"
+#define OPT_STRING "p:hvwgle:"
 #endif
 
 #define VERBOSITY_ENV_VAR "TINI_VERBOSITY"
@@ -71,6 +105,7 @@ static int32_t expect_status[(STATUS_MAX - STATUS_MIN + 1) / 32];
 #if HAS_SUBREAPER
 static unsigned int subreaper = 0;
 #endif
+static unsigned int parent_death_signal = 0;
 static unsigned int kill_process_group = 0;
 
 static unsigned int warn_on_reap = 0;
@@ -207,6 +242,7 @@ void print_usage(char* const name, FILE* const file) {
 #if HAS_SUBREAPER
 	fprintf(file, "  -s: Register as a process subreaper (requires Linux >= 3.4).\n");
 #endif
+	fprintf(file, "  -p SIGNAL: Trigger SIGNAL when parent dies, e.g. \"-p SIGKILL\".\n");
 	fprintf(file, "  -v: Generate more verbose output. Repeat up to 3 times.\n");
 	fprintf(file, "  -w: Print a warning when processes are getting reaped.\n");
 	fprintf(file, "  -g: Send signals to the child's process group.\n");
@@ -235,6 +271,20 @@ void print_license(FILE* const file) {
     }
 }
 
+int set_pdeathsig(char* const arg) {
+	size_t i;
+
+	for (i = 0; i < ARRAY_LEN(signal_names); i++) {
+		if (strcmp(signal_names[i].name, arg) == 0) {
+			/* Signals start at value "1" */
+			parent_death_signal = signal_names[i].number;
+			return 0;
+		}
+	}
+
+	return 1;
+}
+
 int add_expect_status(char* arg) {
 	long status = 0;
 	char* endptr = NULL;
@@ -276,6 +326,14 @@ int parse_args(const int argc, char* const argv[], char* (**child_args_ptr_ptr)[
 				subreaper++;
 				break;
 #endif
+			case 'p':
+				if (set_pdeathsig(optarg)) {
+					PRINT_FATAL("Not a valid option for -p: %s", optarg);
+					*parse_fail_exitcode_ptr = 1;
+					return 1;
+				}
+				break;
+
 			case 'v':
 				verbosity++;
 				break;
@@ -575,6 +633,12 @@ int main(int argc, char *argv[]) {
 		return 1;
 	}
 
+	/* Trigger signal on this process when the parent process exits. */
+	if (parent_death_signal && prctl(PR_SET_PDEATHSIG, parent_death_signal)) {
+		PRINT_FATAL("Failed to set up parent death signal");
+		return 1;
+	 }
+
 #if HAS_SUBREAPER
 	/* If available and requested, register as a subreaper */
 	if (register_subreaper()) {

test/pdeathsignal/stage_1.py

@@ -0,0 +1,30 @@
+#!/usr/bin/env python
+from __future__ import print_function
+
+import os
+import sys
+import subprocess
+
+
+def main():
+    pid = os.getpid()
+
+    tini = sys.argv[1]
+    ret = sys.argv[2]
+    stage_2 = os.path.join(os.path.dirname(__file__), "stage_2.py")
+
+    cmd = [
+        tini,
+        "-vvv",
+        "-p",
+        "SIGUSR1",
+        "--",
+        stage_2,
+        str(pid),
+        ret
+    ]
+
+    subprocess.Popen(cmd).wait()
+
+if __name__ == "__main__":
+    main()

test/pdeathsignal/stage_2.py

@@ -0,0 +1,25 @@
+#!/usr/bin/env python
+from __future__ import print_function
+
+import os
+import sys
+import signal
+import time
+
+
+def main():
+    ret = sys.argv[2]
+
+    def handler(*args):
+        with open(ret, "w") as f:
+            f.write("ok")
+        sys.exit(0)
+
+    signal.signal(signal.SIGUSR1, handler)
+    pid = int(sys.argv[1])
+
+    os.kill(pid, signal.SIGKILL)
+    time.sleep(5)
+
+if __name__ == "__main__":
+    main()

test/run_inner_tests.py

@@ -9,6 +9,7 @@
 import bitmap
 import re
 import itertools
+import tempfile
 
 DEVNULL = open(os.devnull, 'wb')
 
@@ -133,7 +134,7 @@ def main():
     assert ret == 1, "Reaping test succeeded (it should have failed)!"
 
     # Test that the signals are properly in place here.
-    print "running signal configuration test"
+    print "Running signal configuration test"
 
     p = subprocess.Popen([os.path.join(build, "sigconf-test"), tini, "cat", "/proc/self/status"], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
     out, err = p.communicate()
@@ -156,6 +157,21 @@ def main():
             # Use signum - 1 because the bitmap is 0-indexed but represents signals strting at 1
             assert (signum - 1) in props[signal_set_name].nonzero(), "{0} ({1}) is missing in {2}!".format(SIGNUM_TO_SIGNAME[signum], signum, signal_set_name)
 
+    # Test parent death signal handling.
+    if not args_disabled:
+        print "Running parent death signal test"
+        f = tempfile.NamedTemporaryFile()
+        try:
+            p = subprocess.Popen(
+                [os.path.join(src, "test", "pdeathsignal", "stage_1.py"), tini, f.name],
+                stdout=DEVNULL, stderr=DEVNULL
+            )
+            p.wait()
+
+            busy_wait(lambda: open(f.name).read() == "ok", 10)
+        finally:
+            f.close()
+
     print "---------------------------"
     print "All done, tests as expected"
     print "---------------------------"

tpl/README.md.in

@@ -175,6 +175,20 @@ closely to what happens when you do ctrl-C etc. in a terminal: The
 signal is sent to the foreground process group.
 
 
+### Parent Death Signal ###
+
+Tini can set its parent death signal, which is the signal Tini should receive
+when *its* parent exits. To set the parent death signal, use the `-p` flag with
+the name of the signal Tini should receive when its parent exits:
+
+```
+tini -p SIGTERM -- ...
+```
+
+*NOTE: See [this PR discussion][12] to learn more about the parent death signal
+and use cases.*
+
+
 More
 ----
 
@@ -257,6 +271,7 @@ Contributors:
   + [David Wragg][31]
   + [Michael Crosby][32]
   + [Wyatt Preul][33]
+  + [Patrick Steinhardt][34]
 
 Special thanks to:
 
@@ -268,10 +283,12 @@ Special thanks to:
   [5]: https://docs.docker.com/engine/reference/commandline/run/
   [10]: https://github.com/krallin/tini-images
   [11]: https://github.com/krallin/tini/releases
+  [12]: https://github.com/krallin/tini/pull/114
   [20]: https://github.com/krallin/
   [30]: https://github.com/tianon
   [31]: https://github.com/dpw
   [32]: https://github.com/crosbymichael
   [33]: https://github.com/geek
+  [34]: https://github.com/pks-t
   [40]: https://github.com/danilobuerger
   [41]: https://github.com/datakurre