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NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |NOTES |HISTORY |SEE ALSO |NOTES |COLOPHON | |
SD_EVENT_SOURCE_UNREF(3) sd_event_source_unrefSD_EVENT_SOURCE_UNREF(3)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
#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*sd_event_source_disable_unref(sd_event_source *source);void sd_event_source_disable_unrefp(sd_event_source **source);
sd_event_source_unref()may be used to decrement by one the internal reference counter of the event source object specified assource. The reference counter is initially set to one, when the event source is created with calls such assd_event_add_io(3) orsd_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 tosd_event_source_unref()but takes a pointer to a pointer to ansd_event_sourceobject. This call is useful in conjunction with GCC's and LLVM'sClean-upVariable 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 assource.sd_event_source_unref(),sd_bus_creds_unrefp()andsd_bus_creds_ref()execute no operation if the passed event source object isNULL. 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 ofsd_event_source_unref()with a prior call tosd_event_source_set_enabled()withSD_EVENT_OFFor callsd_event_source_disable_unref(), see below.sd_event_source_disable_unref()combines a call tosd_event_source_set_enabled()withSD_EVENT_OFFwithsd_event_source_unref(). This ensures that the source is disabled before the local reference to it is lost. Thesource parameter is allowed to beNULL.sd_event_source_disable_unrefp()is similar tosd_event_source_unrefp(), but in addition disables the source first. This call is useful in conjunction with GCC's and LLVM'sClean-up Variable Attribute[1]. Note that this function is defined as inline function.
sd_event_source_unref()andsd_event_source_disable_unref()always returnNULL.sd_event_source_ref()always returns the event source object passed in.
Functions described here are available as a shared library, which can be compiled against and linked to with thelibsystemd pkg-config(1) file. The code described here usesgetenv(3), which is declared to be not multi-thread-safe. This means that the code calling the functions described here must not callsetenv(3) from a parallel thread. It is recommended to only do calls tosetenv()from an early phase of the program when no other threads have been started.
sd_event_source_unref(),sd_event_source_unrefp(), andsd_event_source_ref()were added in version 229.sd_event_source_disable_unref()andsd_event_source_disable_unrefp()were added in version 243.
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_enabled(3)
1. Clean-up Variable Attributehttps://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html
This page is part of thesystemd (systemd system and service manager) project. Information about the project can be found at ⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a bug report for this manual page, see ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩. This page was obtained from the project's upstream Git repository ⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that time, the date of the most recent commit that was found in the repository was 2025-08-11.) 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 isnot part of the original manual page), send a mail to man-pages@man7.orgsystemd 258~rc2SD_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)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |