sd_event_source_get_floating(3) — Linux manual page



NAME         top

       sd_event_source_set_floating, sd_event_source_get_floating - Set or
       retrieve 'floating' state of event sources

SYNOPSIS         top

       #include <systemd/sd-event.h>

       int sd_event_source_set_floating(sd_event_source *source,
                                        int floating);

       int sd_event_source_get_floating(sd_event_source *source);

DESCRIPTION         top

       sd_event_source_set_floating() takes a boolean and sets the
       'floating' state of the specified event source object. This is used
       to change the direction of reference counts for the object and the
       event loop it is associated with. In non-floating mode, the event
       source object holds a reference to the event loop object, but not
       vice versa. The creator of the event source object must hold a
       reference to it as long as the source should exist. In floating mode,
       the event loop holds a reference to the source object, and will
       decrease the reference count when being freed. This means that a
       reference to the event loop should be held to prevent both from being

       Various calls that allocate event source objects (i.e.
       sd_event_add_io(3), sd_event_add_time(3) and similar) will
       automatically set an event source object to 'floating' mode if the
       caller passed NULL in the parameter used to return a reference to the
       event source object. Nevertheless, it may be necessary to gain
       temporary access to the source object, for example to adjust event
       source properties after allocation (e.g. its priority or description
       string). In those cases the object may be created in non-floating
       mode, and the returned reference used to adjust the properties, and
       the object marked as floating afterwards, and the reference in the
       caller dropped.

       sd_event_source_get_floating() may be used to query the current
       'floating' state of the event source object source. It returns zero
       if 'floating' mode is off, positive if it is on.

RETURN VALUE         top

       On success, sd_event_source_set_floating() and
       sd_event_source_get_floating() return a non-negative integer. On
       failure, they return a negative errno-style error code.

       Returned errors may indicate the following problems:

           source is not a valid pointer to an sd_event_source object.

           The event loop has been created in a different process.

NOTES         top

       These APIs are implemented as a shared library, which can be compiled
       and linked to with the libsystemd pkg-config(1) file.

SEE ALSO         top

       sd-event(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_event_source_set_description(3), sd_event_source_set_priority(3)

COLOPHON         top

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systemd 246                                  SD_EVENT_SOURCE_SET_FLOATING(3)

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