sleep: introduce SuspendEstimationSec=

Before v252, HibernateDelaySec= specifies the maximum timespan that the
system in suspend state, and the system hibernate after the timespan.

However, after 96d662fa4c, the setting is
repurposed as the default interval to measure battery charge level and
estimate the battery discharging late. And if the system has enough
battery capacity, then the system will stay in suspend state and not
hibernate even if the time passed. See issue #25269.

To keep the backward compatibility, let's introduce another setting
SuspendEstimationSec= for controlling the interval to measure
battery charge level, and make HibernateDelaySec= work as of v251.

This also drops implementation details from the man page.

Fixes #25269.

src/shared/sleep-config.c

@@ -65,10 +65,14 @@ int parse_sleep_config(SleepConfig **ret_sleep_config) {
         int allow_suspend = -1, allow_hibernate = -1,
             allow_s2h = -1, allow_hybrid_sleep = -1;
 
-        sc = new0(SleepConfig, 1);
+        sc = new(SleepConfig, 1);
         if (!sc)
                 return log_oom();
 
+        *sc = (SleepConfig) {
+                .hibernate_delay_usec = USEC_INFINITY,
+        };
+
         const ConfigTableItem items[] = {
                 { "Sleep", "AllowSuspend",              config_parse_tristate, 0, &allow_suspend                  },
                 { "Sleep", "AllowHibernation",          config_parse_tristate, 0, &allow_hibernate                },
@@ -83,6 +87,7 @@ int parse_sleep_config(SleepConfig **ret_sleep_config) {
                 { "Sleep", "HybridSleepState",          config_parse_strv,     0, sc->states + SLEEP_HYBRID_SLEEP },
 
                 { "Sleep", "HibernateDelaySec",         config_parse_sec,      0, &sc->hibernate_delay_usec       },
+                { "Sleep", "SuspendEstimationSec",      config_parse_sec,      0, &sc->suspend_estimation_usec    },
                 {}
         };
 
@@ -113,8 +118,8 @@ int parse_sleep_config(SleepConfig **ret_sleep_config) {
                 sc->modes[SLEEP_HYBRID_SLEEP] = strv_new("suspend", "platform", "shutdown");
         if (!sc->states[SLEEP_HYBRID_SLEEP])
                 sc->states[SLEEP_HYBRID_SLEEP] = strv_new("disk");
-        if (sc->hibernate_delay_usec == 0)
-                sc->hibernate_delay_usec = 2 * USEC_PER_HOUR;
+        if (sc->suspend_estimation_usec == 0)
+                sc->suspend_estimation_usec = DEFAULT_SUSPEND_ESTIMATION_USEC;
 
         /* Ensure values set for all required fields */
         if (!sc->states[SLEEP_SUSPEND] || !sc->modes[SLEEP_HIBERNATE]

src/shared/sleep-config.h

@@ -6,6 +6,8 @@
 #include "hashmap.h"
 #include "time-util.h"
 
+#define DEFAULT_SUSPEND_ESTIMATION_USEC (1 * USEC_PER_HOUR)
+
 typedef enum SleepOperation {
         SLEEP_SUSPEND,
         SLEEP_HIBERNATE,
@@ -20,6 +22,7 @@ typedef struct SleepConfig {
         char **modes[_SLEEP_OPERATION_MAX];
         char **states[_SLEEP_OPERATION_MAX];
         usec_t hibernate_delay_usec;
+        usec_t suspend_estimation_usec;
 } SleepConfig;
 
 SleepConfig* free_sleep_config(SleepConfig *sc);

src/sleep/sleep.c

@@ -267,10 +267,13 @@ static int execute(
 }
 
 static int custom_timer_suspend(const SleepConfig *sleep_config) {
+        usec_t hibernate_timestamp;
         int r;
 
         assert(sleep_config);
 
+        hibernate_timestamp = usec_add(now(CLOCK_BOOTTIME), sleep_config->hibernate_delay_usec);
+
         while (battery_is_low() == 0) {
                 _cleanup_hashmap_free_ Hashmap *last_capacity = NULL, *current_capacity = NULL;
                 _cleanup_close_ int tfd = -EBADF;
@@ -287,14 +290,25 @@ static int custom_timer_suspend(const SleepConfig *sleep_config) {
                 if (r < 0)
                         return log_error_errno(r, "Error fetching battery capacity percentage: %m");
 
-                r = get_total_suspend_interval(last_capacity, &suspend_interval);
-                if (r < 0) {
-                        log_debug_errno(r, "Failed to estimate suspend interval using previous discharge rate, ignoring: %m");
-                        /* In case of no battery or any errors, system suspend interval will be set to HibernateDelaySec=. */
-                        suspend_interval = sleep_config->hibernate_delay_usec;
+                if (hashmap_isempty(last_capacity))
+                        /* In case of no battery, system suspend interval will be set to HibernateDelaySec= or 2 hours. */
+                        suspend_interval = timestamp_is_set(hibernate_timestamp) ? sleep_config->hibernate_delay_usec : DEFAULT_SUSPEND_ESTIMATION_USEC;
+                else {
+                        r = get_total_suspend_interval(last_capacity, &suspend_interval);
+                        if (r < 0) {
+                                log_debug_errno(r, "Failed to estimate suspend interval using previous discharge rate, ignoring: %m");
+                                /* In case of any errors, especially when we do not know the battery
+                                 * discharging rate, system suspend interval will be set to
+                                 * SuspendEstimationSec=. */
+                                suspend_interval = sleep_config->suspend_estimation_usec;
+                        }
                 }
 
+                /* Do not suspend more than HibernateDelaySec= */
                 usec_t before_timestamp = now(CLOCK_BOOTTIME);
+                suspend_interval = MIN(suspend_interval, usec_sub_unsigned(hibernate_timestamp, before_timestamp));
+                if (suspend_interval <= 0)
+                        break; /* system should hibernate */
 
                 log_debug("Set timerfd wake alarm for %s", FORMAT_TIMESPAN(suspend_interval, USEC_PER_SEC));
                 /* Wake alarm for system with or without battery to hibernate or estimate discharge rate whichever is applicable */
@@ -380,7 +394,7 @@ static int freeze_thaw_user_slice(const char **method) {
 
 static int execute_s2h(const SleepConfig *sleep_config) {
         _unused_ _cleanup_(freeze_thaw_user_slice) const char *auto_method_thaw = "ThawUnit";
-        int r, k;
+        int r;
 
         assert(sleep_config);
 
@@ -388,15 +402,21 @@ static int execute_s2h(const SleepConfig *sleep_config) {
         if (r < 0)
                 log_debug_errno(r, "Failed to freeze unit user.slice, ignoring: %m");
 
-        r = check_wakeup_type();
-        if (r < 0)
-                log_debug_errno(r, "Failed to check hardware wakeup type, ignoring: %m");
+        /* Only check if we have automated battery alarms if HibernateDelaySec= is not set, as in that case
+         * we'll busy poll for the configured interval instead */
+        if (!timestamp_is_set(sleep_config->hibernate_delay_usec)) {
+                r = check_wakeup_type();
+                if (r < 0)
+                        log_debug_errno(r, "Failed to check hardware wakeup type, ignoring: %m");
+                else {
+                        r = battery_trip_point_alarm_exists();
+                        if (r < 0)
+                                log_debug_errno(r, "Failed to check whether acpi_btp support is enabled or not, ignoring: %m");
+                }
+        } else
+                r = 0;  /* Force fallback path */
 
-        k = battery_trip_point_alarm_exists();
-        if (k < 0)
-                log_debug_errno(k, "Failed to check whether acpi_btp support is enabled or not, ignoring: %m");
-
-        if (r >= 0 && k > 0) {
+        if (r > 0) { /* If we have both wakeup alarms and battery trip point support, use them */
                 log_debug("Attempting to suspend...");
                 r = execute(sleep_config, SLEEP_SUSPEND, NULL);
                 if (r < 0)

src/sleep/sleep.conf

@@ -23,4 +23,5 @@
 #HibernateState=disk
 #HybridSleepMode=suspend platform shutdown
 #HybridSleepState=disk
-#HibernateDelaySec=120min
+#HibernateDelaySec=
+#SuspendEstimationSec=60min