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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
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 <<EOD
        /*
         * 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
This commit is contained in:
Michal Koutný
2018-11-02 20:56:08 +01:00
committed by Lennart Poettering
parent b390455cbb
commit aa1f95d264
1 changed files with 10 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
src/core/timer.c
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@@ -263,7 +263,7 @@ 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);
@@ -275,7 +275,7 @@ 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);
@@ -331,7 +331,7 @@ 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;
@@ -441,7 +441,8 @@ 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 */
@@ -639,7 +640,7 @@ static int timer_start(Unit *u) {
}
t->result = TIMER_SUCCESS;
timer_enter_waiting(t, true, false);
timer_enter_waiting(t, false);
return 1;
}
@@ -754,14 +755,14 @@ 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;
@@ -803,7 +804,7 @@ 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) {
@@ -815,7 +816,7 @@ 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] = {