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Merge pull request #16536 from poettering/time-clock-map-fixes 

time-util: clock mapping improvements
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2020-07-22 13:05:13 +02:00 committed by GitHub
parent 2859bb932b 58afc4f8e4
commit 3bb4126262
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GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 108 additions and 30 deletions
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82
src/basic/time-util.c
View File

@ -82,43 +82,82 @@ triple_timestamp* triple_timestamp_get(triple_timestamp *ts) {
return ts;
}
static usec_t map_clock_usec_internal(usec_t from, usec_t from_base, usec_t to_base) {
/* Maps the time 'from' between two clocks, based on a common reference point where the first clock
* is at 'from_base' and the second clock at 'to_base'. Basically calculates:
*
* from - from_base + to_base
*
* But takes care of overflows/underflows and avoids signed operations. */
if (from >= from_base) { /* In the future */
usec_t delta = from - from_base;
if (to_base >= USEC_INFINITY - delta) /* overflow? */
return USEC_INFINITY;
return to_base + delta;
} else { /* In the past */
usec_t delta = from_base - from;
if (to_base <= delta) /* underflow? */
return 0;
return to_base - delta;
}
}
usec_t map_clock_usec(usec_t from, clockid_t from_clock, clockid_t to_clock) {
/* Try to avoid any inaccuracy needlessly added in case we convert from effectively the same clock
* onto itself */
if (map_clock_id(from_clock) == map_clock_id(to_clock))
return from;
/* Keep infinity as is */
if (from == USEC_INFINITY)
return from;
return map_clock_usec_internal(from, now(from_clock), now(to_clock));
}
dual_timestamp* dual_timestamp_from_realtime(dual_timestamp *ts, usec_t u) {
int64_t delta;
assert(ts);
if (u == USEC_INFINITY || u <= 0) {
if (u == USEC_INFINITY || u == 0) {
ts->realtime = ts->monotonic = u;
return ts;
}
ts->realtime = u;
delta = (int64_t) now(CLOCK_REALTIME) - (int64_t) u;
ts->monotonic = usec_sub_signed(now(CLOCK_MONOTONIC), delta);
ts->monotonic = map_clock_usec(u, CLOCK_REALTIME, CLOCK_MONOTONIC);
return ts;
}
triple_timestamp* triple_timestamp_from_realtime(triple_timestamp *ts, usec_t u) {
int64_t delta;
usec_t nowr;
assert(ts);
if (u == USEC_INFINITY || u <= 0) {
if (u == USEC_INFINITY || u == 0) {
ts->realtime = ts->monotonic = ts->boottime = u;
return ts;
}
nowr = now(CLOCK_REALTIME);
ts->realtime = u;
delta = (int64_t) now(CLOCK_REALTIME) - (int64_t) u;
ts->monotonic = usec_sub_signed(now(CLOCK_MONOTONIC), delta);
ts->boottime = clock_boottime_supported() ? usec_sub_signed(now(CLOCK_BOOTTIME), delta) : USEC_INFINITY;
ts->monotonic = map_clock_usec_internal(u, nowr, now(CLOCK_MONOTONIC));
ts->boottime = clock_boottime_supported() ?
map_clock_usec_internal(u, nowr, now(CLOCK_BOOTTIME)) :
USEC_INFINITY;
return ts;
}
dual_timestamp* dual_timestamp_from_monotonic(dual_timestamp *ts, usec_t u) {
int64_t delta;
assert(ts);
if (u == USEC_INFINITY) {
@ -127,25 +166,28 @@ dual_timestamp* dual_timestamp_from_monotonic(dual_timestamp *ts, usec_t u) {
}
ts->monotonic = u;
delta = (int64_t) now(CLOCK_MONOTONIC) - (int64_t) u;
ts->realtime = usec_sub_signed(now(CLOCK_REALTIME), delta);
ts->realtime = map_clock_usec(u, CLOCK_MONOTONIC, CLOCK_REALTIME);
return ts;
}
dual_timestamp* dual_timestamp_from_boottime_or_monotonic(dual_timestamp *ts, usec_t u) {
int64_t delta;
clockid_t cid;
usec_t nowm;
if (u == USEC_INFINITY) {
ts->realtime = ts->monotonic = USEC_INFINITY;
return ts;
}
dual_timestamp_get(ts);
delta = (int64_t) now(clock_boottime_or_monotonic()) - (int64_t) u;
ts->realtime = usec_sub_signed(ts->realtime, delta);
ts->monotonic = usec_sub_signed(ts->monotonic, delta);
cid = clock_boottime_or_monotonic();
nowm = now(cid);
if (cid == CLOCK_MONOTONIC)
ts->monotonic = u;
else
ts->monotonic = map_clock_usec_internal(u, nowm, now(CLOCK_MONOTONIC));
ts->realtime = map_clock_usec_internal(u, nowm, now(CLOCK_REALTIME));
return ts;
}

6
src/basic/time-util.h
View File

@ -29,8 +29,8 @@ typedef struct triple_timestamp {
usec_t boottime;
} triple_timestamp;
#define USEC_INFINITY ((usec_t) -1)
#define NSEC_INFINITY ((nsec_t) -1)
#define USEC_INFINITY ((usec_t) UINT64_MAX)
#define NSEC_INFINITY ((nsec_t) UINT64_MAX)
#define MSEC_PER_SEC 1000ULL
#define USEC_PER_SEC ((usec_t) 1000000ULL)
@ -67,6 +67,8 @@ typedef struct triple_timestamp {
usec_t now(clockid_t clock);
nsec_t now_nsec(clockid_t clock);
usec_t map_clock_usec(usec_t from, clockid_t from_clock, clockid_t to_clock);
dual_timestamp* dual_timestamp_get(dual_timestamp *ts);
dual_timestamp* dual_timestamp_from_realtime(dual_timestamp *ts, usec_t u);
dual_timestamp* dual_timestamp_from_monotonic(dual_timestamp *ts, usec_t u);

17
src/core/timer.c
View File

@ -346,7 +346,6 @@ static void timer_enter_waiting(Timer *t, bool time_change) {
bool found_monotonic = false, found_realtime = false;
bool leave_around = false;
triple_timestamp ts;
dual_timestamp dts;
TimerValue *v;
Unit *trigger;
int r;
@ -368,7 +367,7 @@ static void timer_enter_waiting(Timer *t, bool time_change) {
continue;
if (v->base == TIMER_CALENDAR) {
usec_t b;
usec_t b, rebased;
/* If we know the last time this was
* triggered, schedule the job based relative
@ -388,12 +387,14 @@ static void timer_enter_waiting(Timer *t, bool time_change) {
if (r < 0)
continue;
/* To make the delay due to RandomizedDelaySec= work even at boot,
* if the scheduled time has already passed, set the time when systemd
* first started as the scheduled time. */
dual_timestamp_from_monotonic(&dts, UNIT(t)->manager->timestamps[MANAGER_TIMESTAMP_USERSPACE].monotonic);
if (v->next_elapse < dts.realtime)
v->next_elapse = dts.realtime;
/* To make the delay due to RandomizedDelaySec= work even at boot, if the scheduled
* time has already passed, set the time when systemd first started as the scheduled
* time. Note that we base this on the monotonic timestamp of the boot, not the
* realtime one, since the wallclock might have been off during boot. */
rebased = map_clock_usec(UNIT(t)->manager->timestamps[MANAGER_TIMESTAMP_USERSPACE].monotonic,
CLOCK_MONOTONIC, CLOCK_REALTIME);
if (v->next_elapse < rebased)
v->next_elapse = rebased;
if (!found_realtime)
t->next_elapse_realtime = v->next_elapse;

33
src/test/test-time-util.c
View File

@ -483,6 +483,38 @@ static void test_in_utc_timezone(void) {
assert_se(unsetenv("TZ") >= 0);
}
static void test_map_clock_usec(void) {
usec_t nowr, x, y, z;
log_info("/* %s */", __func__);
nowr = now(CLOCK_REALTIME);
x = nowr; /* right now */
y = map_clock_usec(x, CLOCK_REALTIME, CLOCK_MONOTONIC);
z = map_clock_usec(y, CLOCK_MONOTONIC, CLOCK_REALTIME);
/* Converting forth and back will introduce inaccuracies, since we cannot query both clocks atomically, but it should be small. Even on the slowest CI smaller than 1h */
assert_se((z > x ? z - x : x - z) < USEC_PER_HOUR);
assert_se(nowr < USEC_INFINITY - USEC_PER_DAY*7); /* overflow check */
x = nowr + USEC_PER_DAY*7; /* 1 week from now */
y = map_clock_usec(x, CLOCK_REALTIME, CLOCK_MONOTONIC);
assert_se(y > 0 && y < USEC_INFINITY);
z = map_clock_usec(y, CLOCK_MONOTONIC, CLOCK_REALTIME);
assert_se(z > 0 && z < USEC_INFINITY);
assert_se((z > x ? z - x : x - z) < USEC_PER_HOUR);
assert_se(nowr > USEC_PER_DAY * 7); /* underflow check */
x = nowr - USEC_PER_DAY*7; /* 1 week ago */
y = map_clock_usec(x, CLOCK_REALTIME, CLOCK_MONOTONIC);
if (y != 0) { /* might underflow if machine is not up long enough for the monotonic clock to be beyond 1w */
assert_se(y < USEC_INFINITY);
z = map_clock_usec(y, CLOCK_MONOTONIC, CLOCK_REALTIME);
assert_se(z > 0 && z < USEC_INFINITY);
assert_se((z > x ? z - x : x - z) < USEC_PER_HOUR);
}
}
int main(int argc, char *argv[]) {
test_setup_logging(LOG_INFO);
@ -511,6 +543,7 @@ int main(int argc, char *argv[]) {
test_deserialize_dual_timestamp();
test_usec_shift_clock();
test_in_utc_timezone();
test_map_clock_usec();
/* Ensure time_t is signed */
assert_cc((time_t) -1 < (time_t) 1);