1SD_EVENT_SET_WATCHDOG(3) sd_event_set_watchdog SD_EVENT_SET_WATCHDOG(3)
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6 sd_event_set_watchdog, sd_event_get_watchdog - Enable event loop
7 watchdog support
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10 #include <systemd/sd-event.h>
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12 int sd_event_set_watchdog(sd_event *event, int b);
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14 int sd_event_get_watchdog(sd_event *event);
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17 sd_event_set_watchdog() may be used to enable or disable automatic
18 watchdog notification support in the event loop object specified in the
19 event parameter. Specifically, depending on the b boolean argument this
20 will make sure the event loop wakes up in regular intervals and sends
21 watchdog notification messages to the service manager, if this was
22 requested by the service manager. Watchdog support is determined with
23 sd_watchdog_enabled(3), and watchdog messages are sent with
24 sd_notify(3). See the WatchdogSec= setting in systemd.service(5) for
25 details on how to enable watchdog support for a service and the
26 protocol used. The wake-up interval is chosen as half the watchdog
27 timeout declared by the service manager via the $WATCHDOG_USEC
28 environment variable. If the service manager did not request watchdog
29 notifications, or if the process was not invoked by the service manager
30 this call with a true b parameter executes no operation. Passing a
31 false b parameter will disable the automatic sending of watchdog
32 notification messages if it was enabled before. Newly allocated event
33 loop objects have this feature disabled.
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35 The first watchdog notification message is sent immediately when
36 sd_event_set_watchdog() is invoked with a true b parameter.
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38 The watchdog logic is designed to allow the service manager to
39 automatically detect services that ceased processing of incoming
40 events, and thus appear "hung". Watchdog notifications are sent out
41 only at the beginning of each event loop iteration. If an event source
42 dispatch function blocks for an excessively long time and does not
43 return execution to the event loop quickly, this might hence cause the
44 notification message to be delayed, and possibly result in abnormal
45 program termination, as configured in the service unit file.
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47 sd_event_get_watchdog() may be used to determine whether watchdog
48 support was previously requested by a call to sd_event_set_watchdog()
49 with a true b parameter and successfully enabled.
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52 On success, sd_event_set_watchdog() and sd_event_get_watchdog() return
53 a non-zero positive integer if the service manager requested watchdog
54 support and watchdog support was successfully enabled. They return zero
55 if the service manager did not request watchdog support, or if watchdog
56 support was explicitly disabled with a false b parameter. On failure,
57 they return a negative errno-style error code.
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59 Errors
60 Returned errors may indicate the following problems:
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62 -ECHILD
63 The event loop has been created in a different process.
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65 -EINVAL
66 The passed event loop object was invalid.
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69 These APIs are implemented as a shared library, which can be compiled
70 and linked to with the libsystemd pkg-config(1) file.
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73 systemd(1), sd-event(3), sd_event_new(3), sd_event_add_io(3),
74 sd_event_add_time(3), sd_event_add_signal(3), sd_event_add_child(3),
75 sd_event_add_inotify(3), sd_event_add_defer(3), sd_watchdog_enabled(3),
76 sd_notify(3), systemd.service(5)
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80systemd 248 SD_EVENT_SET_WATCHDOG(3)