Movatterモバイル変換

sd_event_set_watchdog(3) — Linux manual page

SD_EVENT_SET_WATCHDOG(3)  sd_event_set_watchdogSD_EVENT_SET_WATCHDOG(3)

NAME        top

       sd_event_set_watchdog, sd_event_get_watchdog - Enable event loop       watchdog support

SYNOPSIS        top

#include <systemd/sd-event.h>int sd_event_set_watchdog(sd_event *event, int b);int sd_event_get_watchdog(sd_event *event);

DESCRIPTION        top

sd_event_set_watchdog()may be used to enable or disable automatic       watchdog notification support in the event loop object specified       in theevent parameter. Specifically, depending on theb boolean       argument this will make sure the event loop wakes up in regular       intervals and sends watchdog notification messages to the service       manager, if this was requested by the service manager. Watchdog       support is determined withsd_watchdog_enabled(3), and watchdog       messages are sent withsd_notify(3). See theWatchdogSec= setting       insystemd.service(5) for details on how to enable watchdog       support for a service and the protocol used. The wake-up interval       is chosen as half the watchdog timeout declared by the service       manager via the$WATCHDOG_USEC environment variable. If the       service manager did not request watchdog notifications, or if the       process was not invoked by the service manager this call with a       trueb parameter executes no operation. Passing a falseb       parameter will disable the automatic sending of watchdog       notification messages if it was enabled before. Newly allocated       event loop objects have this feature disabled.       The first watchdog notification message is sent immediately whensd_event_set_watchdog()is invoked with a trueb parameter.       The watchdog logic is designed to allow the service manager to       automatically detect services that ceased processing of incoming       events, and thus appear "hung". Watchdog notifications are sent       out only at the beginning of each event loop iteration. If an       event source dispatch function blocks for an excessively long time       and does not return execution to the event loop quickly, this       might hence cause the notification message to be delayed, and       possibly result in abnormal program termination, as configured in       the service unit file.sd_event_get_watchdog()may be used to determine whether watchdog       support was previously requested by a call tosd_event_set_watchdog()with a trueb parameter and successfully       enabled.

RETURN VALUE        top

       On success,sd_event_set_watchdog()andsd_event_get_watchdog()       return a non-zero positive integer if the service manager       requested watchdog support and watchdog support was successfully       enabled. They return zero if the service manager did not request       watchdog support, or if watchdog support was explicitly disabled       with a falseb parameter. On failure, they return a negative       errno-style error code.Errors       Returned errors may indicate the following problems:-ECHILD           The event loop has been created in a different process,           library or module instance.-EINVAL           The passed event loop object was invalid.

NOTES        top

       Functions described here are available as a shared library, which       can be compiled against and linked to with thelibsystemd pkg-config(1) file.       The code described here usesgetenv(3), which is declared to be       not multi-thread-safe. This means that the code calling the       functions described here must not callsetenv(3) from a parallel       thread. It is recommended to only do calls tosetenv()from an       early phase of the program when no other threads have been       started.

HISTORY        top

sd_event_set_watchdog()andsd_event_get_watchdog()were added in       version 229.

SEE ALSO        top

systemd(1),sd-event(3),sd_event_new(3),sd_event_add_io(3),sd_event_add_time(3),sd_event_add_signal(3),sd_event_add_child(3),sd_event_add_inotify(3),sd_event_add_defer(3),sd_watchdog_enabled(3),sd_notify(3),systemd.service(5)

COLOPHON        top

       This page is part of thesystemd (systemd system and service       manager) project.  Information about the project can be found at       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have a       bug report for this manual page, see       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.       This page was obtained from the project's upstream Git repository       ⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11.  (At that       time, the date of the most recent commit that was found in the       repository was 2025-08-11.)  If you discover any rendering       problems in this HTML version of the page, or you believe there is       a better or more up-to-date source for the page, or you have       corrections or improvements to the information in this COLOPHON       (which isnot part of the original manual page), send a mail to       man-pages@man7.orgsystemd 258~rc2SD_EVENT_SET_WATCHDOG(3)

Pages that refer to this page:sd-event(3), sd_watchdog_enabled(3), systemd.service(5), systemd.directives(7), systemd.index(7)

HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH.