From 3d4280d0a487109f8f648147083baf573e4418a3 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Michal=20Koutn=C3=BD?= <mkoutny@suse.com>

Date: Fri, 2 Nov 2018 20:56:08 +0100

Subject: [PATCH] core: Detect initial timer state from serialized data

We keep a mark whether a single-shot timer was triggered in the caller's

variable initial. When such a timer elapses while we are

serializing/deserializing the inner state, we consider the timer

incorrectly as elapsed and don't trigger it later.

This patch exploits last_trigger timestamp that we already serialize,

hence we can eliminate the argument initial completely.

A reproducer for OnBootSec= timers:

        cat >repro.c <

        /*

         * Compile:	gcc repro.c -o repro

         * Run:		./repro

         */

        #include <errno.h>

        #include <fcntl.h>

        #include <stdio.h>

        #include <stdlib.h>

        #include <sys/stat.h>

        #include <sys/types.h>

        #include <time.h>

        #include <unistd.h>

        int main(int argc, char *argv[]) {

        	char command[1024];

        	int pause;

        	struct timespec now;

        	while (1) {

        		usleep(rand() % 200000); // prevent periodic repeats

               		clock_gettime(CLOCK_MONOTONIC, &now;;

        		printf("%i\n", now.tv_sec);

        		system("rm -f $PWD/mark");

        		snprintf(command, 1024, "systemd-run --user --on-boot=%i --timer-property=AccuracySec=100ms "

        					"touch $PWD/mark", now.tv_sec + 1);

        		system(command);

        		system("systemctl --user list-timers");

        		pause = (1000000000 - now.tv_nsec)/1000 - 70000; // fiddle to hit the middle of reloading

        		usleep(pause > 0 ? pause : 0);

        		system("systemctl --user daemon-reload");

        		sync();

        		sleep(2);

        		if (open("./mark", 0) < 0)

        			if (errno == ENOENT) {

        				printf("mark file does not exist\n");

        				break;

        			}

        	}

        	return 0;

        }

        EOD

(cherry picked from commit aa1f95d2647197eca84c33a0f10adaeada08467d)

Resolves: #1899402

---

 src/core/timer.c | 19 ++++++++++---------

 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/src/core/timer.c b/src/core/timer.c

index ef240a6f19..1718ffc5a5 100644

--- a/src/core/timer.c

+++ b/src/core/timer.c

@@ -262,7 +262,7 @@ static void timer_set_state(Timer *t, TimerState state) {

         unit_notify(UNIT(t), state_translation_table[old_state], state_translation_table[state], 0);

 }

-static void timer_enter_waiting(Timer *t, bool initial, bool time_change);

+static void timer_enter_waiting(Timer *t, bool time_change);

 static int timer_coldplug(Unit *u) {

         Timer *t = TIMER(u);

@@ -274,7 +274,7 @@ static int timer_coldplug(Unit *u) {

                 return 0;

         if (t->deserialized_state == TIMER_WAITING)

-                timer_enter_waiting(t, false, false);

+                timer_enter_waiting(t, false);

         else

                 timer_set_state(t, t->deserialized_state);

@@ -334,7 +334,7 @@ static void add_random(Timer *t, usec_t *v) {

         log_unit_debug(UNIT(t), "Adding %s random time.", format_timespan(s, sizeof(s), add, 0));

 }

-static void timer_enter_waiting(Timer *t, bool initial, bool time_change) {

+static void timer_enter_waiting(Timer *t, bool time_change) {

         bool found_monotonic = false, found_realtime = false;

         bool leave_around = false;

         triple_timestamp ts;

@@ -444,7 +444,8 @@ static void timer_enter_waiting(Timer *t, bool initial, bool time_change) {

                         v->next_elapse = usec_add(usec_shift_clock(base, CLOCK_MONOTONIC, TIMER_MONOTONIC_CLOCK(t)), v->value);

-                        if (!initial && !time_change &&

+                        if (dual_timestamp_is_set(&t->last_trigger) &&

+                            !time_change &&

                             v->next_elapse < triple_timestamp_by_clock(&ts, TIMER_MONOTONIC_CLOCK(t)) &&

                             IN_SET(v->base, TIMER_ACTIVE, TIMER_BOOT, TIMER_STARTUP)) {

                                 /* This is a one time trigger, disable it now */

@@ -642,7 +643,7 @@ static int timer_start(Unit *u) {

         }

         t->result = TIMER_SUCCESS;

-        timer_enter_waiting(t, true, false);

+        timer_enter_waiting(t, false);

         return 1;

 }

@@ -764,14 +765,14 @@ static void timer_trigger_notify(Unit *u, Unit *other) {

         case TIMER_ELAPSED:

                 /* Recalculate sleep time */

-                timer_enter_waiting(t, false, false);

+                timer_enter_waiting(t, false);

                 break;

         case TIMER_RUNNING:

                 if (UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(other))) {

                         log_unit_debug(UNIT(t), "Got notified about unit deactivation.");

-                        timer_enter_waiting(t, false, false);

+                        timer_enter_waiting(t, false);

                 }

                 break;

@@ -813,7 +814,7 @@ static void timer_time_change(Unit *u) {

                 t->last_trigger.realtime = ts;

         log_unit_debug(u, "Time change, recalculating next elapse.");

-        timer_enter_waiting(t, false, true);

+        timer_enter_waiting(t, true);

 }

 static void timer_timezone_change(Unit *u) {

@@ -825,7 +826,7 @@ static void timer_timezone_change(Unit *u) {

                 return;

         log_unit_debug(u, "Timezone change, recalculating next elapse.");

-        timer_enter_waiting(t, false, false);

+        timer_enter_waiting(t, false);

 }

 static const char* const timer_base_table[_TIMER_BASE_MAX] = {