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From 3d4280d0a487109f8f648147083baf573e4418a3 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Michal=20Koutn=C3=BD?= <mkoutny@suse.com>
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Date: Fri, 2 Nov 2018 20:56:08 +0100
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Subject: [PATCH] core: Detect initial timer state from serialized data
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We keep a mark whether a single-shot timer was triggered in the caller's
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variable initial. When such a timer elapses while we are
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serializing/deserializing the inner state, we consider the timer
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incorrectly as elapsed and don't trigger it later.
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This patch exploits last_trigger timestamp that we already serialize,
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hence we can eliminate the argument initial completely.
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A reproducer for OnBootSec= timers:
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        cat >repro.c <
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        /*
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         * Compile:	gcc repro.c -o repro
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         * Run:		./repro
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         */
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        #include <errno.h>
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        #include <fcntl.h>
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        #include <stdio.h>
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        #include <stdlib.h>
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        #include <sys/stat.h>
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        #include <sys/types.h>
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        #include <time.h>
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        #include <unistd.h>
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        int main(int argc, char *argv[]) {
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        	char command[1024];
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        	int pause;
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        	struct timespec now;
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        	while (1) {
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        		usleep(rand() % 200000); // prevent periodic repeats
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               		clock_gettime(CLOCK_MONOTONIC, &now;;
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        		printf("%i\n", now.tv_sec);
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        		system("rm -f $PWD/mark");
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        		snprintf(command, 1024, "systemd-run --user --on-boot=%i --timer-property=AccuracySec=100ms "
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        					"touch $PWD/mark", now.tv_sec + 1);
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        		system(command);
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        		system("systemctl --user list-timers");
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        		pause = (1000000000 - now.tv_nsec)/1000 - 70000; // fiddle to hit the middle of reloading
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        		usleep(pause > 0 ? pause : 0);
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        		system("systemctl --user daemon-reload");
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        		sync();
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        		sleep(2);
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        		if (open("./mark", 0) < 0)
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        			if (errno == ENOENT) {
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        				printf("mark file does not exist\n");
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        				break;
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        			}
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        	}
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        	return 0;
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        }
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        EOD
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(cherry picked from commit aa1f95d2647197eca84c33a0f10adaeada08467d)
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Resolves: #1899402
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---
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 src/core/timer.c | 19 ++++++++++---------
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 1 file changed, 10 insertions(+), 9 deletions(-)
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diff --git a/src/core/timer.c b/src/core/timer.c
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index ef240a6f19..1718ffc5a5 100644
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--- a/src/core/timer.c
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+++ b/src/core/timer.c
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@@ -262,7 +262,7 @@ static void timer_set_state(Timer *t, TimerState state) {
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         unit_notify(UNIT(t), state_translation_table[old_state], state_translation_table[state], 0);
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 }
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-static void timer_enter_waiting(Timer *t, bool initial, bool time_change);
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+static void timer_enter_waiting(Timer *t, bool time_change);
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 static int timer_coldplug(Unit *u) {
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         Timer *t = TIMER(u);
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@@ -274,7 +274,7 @@ static int timer_coldplug(Unit *u) {
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                 return 0;
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         if (t->deserialized_state == TIMER_WAITING)
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-                timer_enter_waiting(t, false, false);
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+                timer_enter_waiting(t, false);
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         else
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                 timer_set_state(t, t->deserialized_state);
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@@ -334,7 +334,7 @@ static void add_random(Timer *t, usec_t *v) {
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         log_unit_debug(UNIT(t), "Adding %s random time.", format_timespan(s, sizeof(s), add, 0));
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 }
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-static void timer_enter_waiting(Timer *t, bool initial, bool time_change) {
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+static void timer_enter_waiting(Timer *t, bool time_change) {
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         bool found_monotonic = false, found_realtime = false;
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         bool leave_around = false;
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         triple_timestamp ts;
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@@ -444,7 +444,8 @@ static void timer_enter_waiting(Timer *t, bool initial, bool time_change) {
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                         v->next_elapse = usec_add(usec_shift_clock(base, CLOCK_MONOTONIC, TIMER_MONOTONIC_CLOCK(t)), v->value);
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-                        if (!initial && !time_change &&
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+                        if (dual_timestamp_is_set(&t->last_trigger) &&
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+                            !time_change &&
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                             v->next_elapse < triple_timestamp_by_clock(&ts, TIMER_MONOTONIC_CLOCK(t)) &&
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                             IN_SET(v->base, TIMER_ACTIVE, TIMER_BOOT, TIMER_STARTUP)) {
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                                 /* This is a one time trigger, disable it now */
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@@ -642,7 +643,7 @@ static int timer_start(Unit *u) {
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         }
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         t->result = TIMER_SUCCESS;
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-        timer_enter_waiting(t, true, false);
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+        timer_enter_waiting(t, false);
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         return 1;
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 }
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@@ -764,14 +765,14 @@ static void timer_trigger_notify(Unit *u, Unit *other) {
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         case TIMER_ELAPSED:
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                 /* Recalculate sleep time */
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-                timer_enter_waiting(t, false, false);
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+                timer_enter_waiting(t, false);
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                 break;
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         case TIMER_RUNNING:
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                 if (UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(other))) {
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                         log_unit_debug(UNIT(t), "Got notified about unit deactivation.");
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-                        timer_enter_waiting(t, false, false);
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+                        timer_enter_waiting(t, false);
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                 }
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                 break;
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@@ -813,7 +814,7 @@ static void timer_time_change(Unit *u) {
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                 t->last_trigger.realtime = ts;
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         log_unit_debug(u, "Time change, recalculating next elapse.");
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-        timer_enter_waiting(t, false, true);
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+        timer_enter_waiting(t, true);
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 }
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 static void timer_timezone_change(Unit *u) {
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@@ -825,7 +826,7 @@ static void timer_timezone_change(Unit *u) {
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                 return;
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         log_unit_debug(u, "Timezone change, recalculating next elapse.");
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-        timer_enter_waiting(t, false, false);
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+        timer_enter_waiting(t, false);
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 }
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 static const char* const timer_base_table[_TIMER_BASE_MAX] = {