sd_event_source_unref(3) — Linux manual page


SD_EVENT_SOURCE_UNREF(3)  sd_event_source_unref SD_EVENT_SOURCE_UNREF(3)

NAME         top

       sd_event_source_unref, sd_event_source_unrefp,
       sd_event_source_ref, sd_event_source_disable_unref,
       sd_event_source_disable_unrefp - Increase or decrease event
       source reference counters

SYNOPSIS         top

       #include <systemd/sd-event.h>

       sd_event_source* sd_event_source_unref(sd_event_source *source);

       void sd_event_source_unrefp(sd_event_source **source);

       sd_event_source* sd_event_source_ref(sd_event_source *source);

                                                      sd_event_source_disable_unref(sd_event_source *source);

       void sd_event_source_disable_unrefp(sd_event_source **source);

DESCRIPTION         top

       sd_event_source_unref() may be used to decrement by one the
       internal reference counter of the event source object specified
       as source. The reference counter is initially set to one, when
       the event source is created with calls such as sd_event_add_io(3)
       or sd_event_add_time(3). When the reference counter reaches zero,
       the object is detached from the event loop object and destroyed.

       sd_event_source_unrefp() is similar to sd_event_source_unref()
       but takes a pointer to a pointer to an sd_event_source object.
       This call is useful in conjunction with GCC's and LLVM's Clean-up
       Variable Attribute[1]. Note that this function is defined as
       inline function.

       sd_event_source_ref() may be used to increase by one the internal
       reference counter of the event source object specified as source.

       sd_event_source_unref(), sd_bus_creds_unrefp() and
       sd_bus_creds_ref() execute no operation if the passed event
       source object is NULL.

       Note that event source objects stay alive and may be dispatched
       as long as they have a reference counter greater than zero. In
       order to drop a reference of an event source and make sure the
       associated event source handler function is not called anymore it
       is recommended to combine a call of sd_event_source_unref() with
       a prior call to sd_event_source_set_enabled() with SD_EVENT_OFF
       or call sd_event_source_disable_unref(), see below.

       sd_event_source_disable_unref() combines a call to
       sd_event_source_set_enabled() with SD_EVENT_OFF with
       sd_event_source_unref(). This ensures that the source is disabled
       before the local reference to it is lost. The source parameter is
       allowed to be NULL.

       sd_event_source_disable_unrefp() is similar to
       sd_event_source_unrefp(), but in addition disables the source
       first. This call is useful in conjunction with GCC's and LLVM's
       Clean-up Variable Attribute[1]. Note that this function is
       defined as inline function.

RETURN VALUE         top

       sd_event_source_unref() and sd_event_source_disable_unref()
       always return NULL.  sd_event_source_ref() always returns the
       event source object passed in.

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_unref(), sd_event_source_unrefp(), and
       sd_event_source_ref() were added in version 229.

       sd_event_source_disable_unref() and
       sd_event_source_disable_unrefp() were added in version 243.

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),

NOTES         top

        1. Clean-up Variable Attribute

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 2024-06-14.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2024-06-13.)  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 257~devel                               SD_EVENT_SOURCE_UNREF(3)

Pages that refer to this page: sd-event(3)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)sd_event_source_get_pending(3)sd_event_source_set_enabled(3)systemd.directives(7)systemd.index(7)