sd_event_source_set_floating(3) — Linux manual page


SD_EVEN...LOATING(3)  sd_event_source_set_floating  SD_EVEN...LOATING(3)

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 destroyed.

       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.

           Added in version 244.

           The event loop has been created in a different process,
           library or module instance.

           Added in version 244.

NOTES         top

       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

HISTORY         top

       sd_event_source_set_floating() and sd_event_source_get_floating()
       were added in version 244.

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),

COLOPHON         top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨⟩.  If you have
       a bug report for this manual page, see
       This page was obtained from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2023-12-22.)  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 is not part of the original manual page), send a mail to

systemd 255                                         SD_EVEN...LOATING(3)

Pages that refer to this page: sd_event_add_child(3)sd_event_add_defer(3)sd_event_add_inotify(3)sd_event_add_io(3)sd_event_add_memory_pressure(3)sd_event_add_signal(3)sd_event_add_time(3)systemd.directives(7)systemd.index(7)