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227 lines
10 KiB
227 lines
10 KiB
From 338b8f9bca1cd7bd65123808fc7f7b2773e637db Mon Sep 17 00:00:00 2001 |
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From: Lennart Poettering <lennart@poettering.net> |
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Date: Wed, 18 Nov 2015 13:37:30 +0100 |
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Subject: [PATCH] core: add new RandomSec= setting for time units |
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This allows configuration of a random time on top of the elapse events, |
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in order to spread time events in a network evenly across a range. |
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Cherry-picked from: 744c7693751830149ae78fdaf95c6c6f99d59f07 |
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Resolves: #1305279 |
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--- |
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man/systemd.timer.xml | 43 ++++++++++++++++++++++++++++++----- |
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src/core/dbus-timer.c | 17 ++++++++++++++ |
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src/core/load-fragment-gperf.gperf.m4 | 1 + |
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src/core/timer.c | 28 +++++++++++++++++++++++ |
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src/core/timer.h | 1 + |
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src/libsystemd/sd-bus/bus-util.c | 16 +++++++++++++ |
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6 files changed, 100 insertions(+), 6 deletions(-) |
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diff --git a/man/systemd.timer.xml b/man/systemd.timer.xml |
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index 20890f227..bdd14d888 100644 |
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--- a/man/systemd.timer.xml |
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+++ b/man/systemd.timer.xml |
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@@ -180,13 +180,12 @@ |
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<varname>OnUnitInactiveSec=</varname> and ending the time |
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configured with <varname>AccuracySec=</varname> later. Within |
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this time window, the expiry time will be placed at a |
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- host-specific, randomized but stable position that is |
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+ host-specific, randomized, but stable position that is |
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synchronized between all local timer units. This is done in |
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- order to distribute the wake-up time in networked |
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- installations, as well as optimizing power consumption to |
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- suppress unnecessary CPU wake-ups. To get best accuracy, set |
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- this option to 1us. Note that the timer is still subject to |
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- the timer slack configured via |
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+ order to optimize power consumption to suppress unnecessary |
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+ CPU wake-ups. To get best accuracy, set this option to |
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+ 1us. Note that the timer is still subject to the timer slack |
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+ configured via |
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<citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>'s |
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<varname>TimerSlackNSec=</varname> setting. See |
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<citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry> |
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@@ -194,6 +193,38 @@ |
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this value as high as possible and as low as |
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necessary.</para></listitem> |
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</varlistentry> |
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+ |
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+ <varlistentry> |
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+ <term><varname>RandomSec=</varname></term> |
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+ |
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+ <listitem><para>Delay the timer by a randomly selected, evenly |
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+ distributed amount of time between 0 and the specified time |
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+ value. Defaults to 0, indicating that no randomized delay |
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+ shall be applied. Each timer unit will determine this delay |
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+ randomly each time it is started, and the delay will simply be |
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+ added on top of the next determined elapsing time. This is |
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+ useful to stretch dispatching of similarly configured timer |
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+ events over a certain amount time, to avoid that they all fire |
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+ at the same time, possibly resulting in resource |
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+ congestion. Note the relation to |
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+ <varname>AccuracySec=</varname> above: the latter allows the |
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+ service manager to coalesce timer events within a specified |
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+ time range in order to minimize wakeups, the former does the |
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+ opposite: it stretches timer events over a time range, to make |
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+ it unlikely that they fire simultaneously. If |
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+ <varname>RandomSec=</varname> and |
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+ <varname>AccuracySec=</varname> are used in conjunction, first |
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+ the a randomized time is added, and the result is then |
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+ possibly shifted further to coalesce it with other timer |
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+ events possibly happening on the system. As mentioned above |
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+ <varname>AccuracySec=</varname> defaults to 1min and |
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+ <varname>RandomSec=</varname> to 0, thus encouraging |
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+ coalescing of timer events. In order to optimally stretch |
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+ timer events over a certain range of time, make sure to set |
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+ <varname>RandomSec=</varname> to a higher value, and |
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+ <varname>AccuracySec=1us</varname>.</para></listitem> |
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+ </varlistentry> |
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+ |
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<varlistentry> |
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<term><varname>Unit=</varname></term> |
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diff --git a/src/core/dbus-timer.c b/src/core/dbus-timer.c |
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index 43e785246..cd7bf44ba 100644 |
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--- a/src/core/dbus-timer.c |
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+++ b/src/core/dbus-timer.c |
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@@ -181,6 +181,7 @@ const sd_bus_vtable bus_timer_vtable[] = { |
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BUS_PROPERTY_DUAL_TIMESTAMP("LastTriggerUSec", offsetof(Timer, last_trigger), SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE), |
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SD_BUS_PROPERTY("Result", "s", property_get_result, offsetof(Timer, result), SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE), |
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SD_BUS_PROPERTY("AccuracyUSec", "t", bus_property_get_usec, offsetof(Timer, accuracy_usec), SD_BUS_VTABLE_PROPERTY_CONST), |
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+ SD_BUS_PROPERTY("RandomUSec", "t", bus_property_get_usec, offsetof(Timer, random_usec), SD_BUS_VTABLE_PROPERTY_CONST), |
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SD_BUS_PROPERTY("Persistent", "b", bus_property_get_bool, offsetof(Timer, persistent), SD_BUS_VTABLE_PROPERTY_CONST), |
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SD_BUS_PROPERTY("WakeSystem", "b", bus_property_get_bool, offsetof(Timer, wake_system), SD_BUS_VTABLE_PROPERTY_CONST), |
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SD_BUS_VTABLE_END |
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@@ -284,6 +285,22 @@ static int bus_timer_set_transient_property( |
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return 1; |
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+ } else if (streq(name, "RandomUSec")) { |
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+ usec_t u = 0; |
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+ |
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+ r = sd_bus_message_read(message, "t", &u); |
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+ if (r < 0) |
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+ return r; |
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+ |
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+ if (mode != UNIT_CHECK) { |
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+ char time[FORMAT_TIMESPAN_MAX]; |
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+ |
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+ t->random_usec = u; |
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+ unit_write_drop_in_private_format(UNIT(t), mode, name, "RandomSec=%s\n", format_timespan(time, sizeof(time), u, USEC_PER_MSEC)); |
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+ } |
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+ |
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+ return 1; |
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+ |
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} else if (streq(name, "WakeSystem")) { |
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int b; |
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diff --git a/src/core/load-fragment-gperf.gperf.m4 b/src/core/load-fragment-gperf.gperf.m4 |
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index 53059845e..5106a98ee 100644 |
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--- a/src/core/load-fragment-gperf.gperf.m4 |
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+++ b/src/core/load-fragment-gperf.gperf.m4 |
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@@ -336,6 +336,7 @@ Timer.OnUnitInactiveSec, config_parse_timer, 0, |
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Timer.Persistent, config_parse_bool, 0, offsetof(Timer, persistent) |
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Timer.WakeSystem, config_parse_bool, 0, offsetof(Timer, wake_system) |
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Timer.AccuracySec, config_parse_sec, 0, offsetof(Timer, accuracy_usec) |
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+Timer.RandomSec, config_parse_sec, 0, offsetof(Timer, random_usec) |
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Timer.Unit, config_parse_trigger_unit, 0, 0 |
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m4_dnl |
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Path.PathExists, config_parse_path_spec, 0, 0 |
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diff --git a/src/core/timer.c b/src/core/timer.c |
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index 48cf9c16a..972dd73df 100644 |
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--- a/src/core/timer.c |
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+++ b/src/core/timer.c |
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@@ -29,6 +29,7 @@ |
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#include "bus-util.h" |
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#include "bus-error.h" |
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#include "mkdir.h" |
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+#include "util.h" |
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static const UnitActiveState state_translation_table[_TIMER_STATE_MAX] = { |
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[TIMER_DEAD] = UNIT_INACTIVE, |
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@@ -315,6 +316,28 @@ static usec_t monotonic_to_boottime(usec_t t) { |
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return 0; |
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} |
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+static void add_random(Timer *t, usec_t *v) { |
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+ char s[FORMAT_TIMESPAN_MAX]; |
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+ usec_t add; |
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+ |
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+ assert(t); |
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+ assert(*v); |
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+ |
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+ if (t->random_usec == 0) |
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+ return; |
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+ if (*v == USEC_INFINITY) |
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+ return; |
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+ |
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+ add = random_u64() % t->random_usec; |
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+ |
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+ if (*v + add < *v) /* overflow */ |
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+ *v = (usec_t) -2; /* Highest possible value, that is not USEC_INFINITY */ |
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+ else |
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+ *v += add; |
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+ |
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+ log_unit_info(UNIT(t)->id, "Adding %s random time.", format_timespan(s, sizeof(s), add, 0)); |
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+} |
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+ |
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static void timer_enter_waiting(Timer *t, bool initial) { |
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bool found_monotonic = false, found_realtime = false; |
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usec_t ts_realtime, ts_monotonic; |
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@@ -431,6 +454,8 @@ static void timer_enter_waiting(Timer *t, bool initial) { |
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if (found_monotonic) { |
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char buf[FORMAT_TIMESPAN_MAX]; |
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+ add_random(t, &t->next_elapse_monotonic_or_boottime); |
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+ |
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log_unit_debug(UNIT(t)->id, "%s: Monotonic timer elapses in %s.", |
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UNIT(t)->id, |
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format_timespan(buf, sizeof(buf), t->next_elapse_monotonic_or_boottime > ts_monotonic ? t->next_elapse_monotonic_or_boottime - ts_monotonic : 0, 0)); |
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@@ -460,6 +485,9 @@ static void timer_enter_waiting(Timer *t, bool initial) { |
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if (found_realtime) { |
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char buf[FORMAT_TIMESTAMP_MAX]; |
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+ |
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+ add_random(t, &t->next_elapse_realtime); |
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+ |
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log_unit_debug(UNIT(t)->id, "%s: Realtime timer elapses at %s.", UNIT(t)->id, format_timestamp(buf, sizeof(buf), t->next_elapse_realtime)); |
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if (t->realtime_event_source) { |
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diff --git a/src/core/timer.h b/src/core/timer.h |
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index de412a043..b97724525 100644 |
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--- a/src/core/timer.h |
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+++ b/src/core/timer.h |
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@@ -69,6 +69,7 @@ struct Timer { |
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Unit meta; |
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usec_t accuracy_usec; |
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+ usec_t random_usec; |
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LIST_HEAD(TimerValue, values); |
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usec_t next_elapse_realtime; |
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diff --git a/src/libsystemd/sd-bus/bus-util.c b/src/libsystemd/sd-bus/bus-util.c |
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index 6d5615082..5ecb3bea4 100644 |
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--- a/src/libsystemd/sd-bus/bus-util.c |
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+++ b/src/libsystemd/sd-bus/bus-util.c |
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@@ -1360,6 +1360,22 @@ int bus_append_unit_property_assignment(sd_bus_message *m, const char *assignmen |
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return -EINVAL; |
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} |
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+ if (r < 0) |
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+ return bus_log_create_error(r); |
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+ |
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+ return 0; |
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+ } else if (streq(field, "RandomSec")) { |
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+ usec_t t; |
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+ |
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+ r = parse_sec(eq, &t); |
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+ if (r < 0) |
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+ return log_error_errno(r, "Failed to parse RandomSec= parameter: %s", eq); |
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+ |
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+ r = sd_bus_message_append_basic(m, SD_BUS_TYPE_STRING, "RandomUSec"); |
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+ if (r < 0) |
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+ return bus_log_create_error(r); |
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+ |
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+ r = sd_bus_message_append(m, "v", "t", t); |
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if (r < 0) |
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return bus_log_create_error(r); |
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