x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_EVENT_SET_WATCHDOG(3) sd_event_set_watchdog SD_EVENT_SET_WATCHDOG(3)
NAME
sd_event_set_watchdog, sd_event_get_watchdog - Enable event loop
watchdog support
SYNOPSIS
#include <systemd/sd-event.h>
int sd_event_set_watchdog(sd_event *event, int b);
int sd_event_get_watchdog(sd_event *event);
DESCRIPTION
sd_event_set_watchdog() may be used to enable or disable automatic
watchdog notification support in the event loop object specified in the
event parameter. Specifically, depending on the b 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 with
sd_watchdog_enabled(3), and watchdog messages are sent with
sd_notify(3). See the WatchdogSec= setting in systemd.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 true b parameter executes no operation. Passing a
false b 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 when
sd_event_set_watchdog() is invoked with a true b 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 to sd_event_set_watchdog()
with a true b parameter and successfully enabled.
RETURN VALUE
On success, sd_event_set_watchdog() and sd_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 false b 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
Functions described here are available as a shared library, which can
be compiled against and linked to with the libsystemd pkg-config(1)
file.
The code described here uses getenv(3), which is declared to be not
multi-thread-safe. This means that the code calling the functions
described here must not call setenv(3) from a parallel thread. It is
recommended to only do calls to setenv() from an early phase of the
program when no other threads have been started.
SEE ALSO
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)
systemd 254 SD_EVENT_SET_WATCHDOG(3)
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