x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_EVENT_SOURCE_SET_PRIORsd_event_source_set_prSD_EVENT_SOURCE_SET_PRIORITY(3)
NAME
sd_event_source_set_priority, sd_event_source_get_priority,
SD_EVENT_PRIORITY_IMPORTANT, SD_EVENT_PRIORITY_NORMAL,
SD_EVENT_PRIORITY_IDLE - Set or retrieve the priority of event sources
SYNOPSIS
#include <systemd/sd-event.h>
enum {
SD_EVENT_PRIORITY_IMPORTANT = -100,
SD_EVENT_PRIORITY_NORMAL = 0,
SD_EVENT_PRIORITY_IDLE = 100,
};
int sd_event_source_set_priority(sd_event_source *source,
int64_t priority);
int sd_event_source_get_priority(sd_event_source *source,
int64_t *priority);
DESCRIPTION
sd_event_source_set_priority() may be used to set the priority for the
event source object specified as source. The priority is specified as
an arbitrary signed 64-bit integer. The priority is initialized to
SD_EVENT_PRIORITY_NORMAL (0) when the event source is allocated with a
call such as sd_event_add_io(3) or sd_event_add_time(3), and may be
changed with this call. If multiple event sources have seen events at
the same time, they are dispatched in the order indicated by the event
sources' priorities. Event sources with smaller priority values are
dispatched first. As well-known points of reference, the constants
SD_EVENT_PRIORITY_IMPORTANT (-100), SD_EVENT_PRIORITY_NORMAL (0) and
SD_EVENT_PRIORITY_IDLE (100) may be used to indicate event sources that
shall be dispatched early, normally or late. It is recommended to
specify priorities based on these definitions, and relative to them --
however, the full 64-bit signed integer range is available for ordering
event sources.
Priorities define the order in which event sources that have seen
events are dispatched. Care should be taken to ensure that
high-priority event sources (those with negative priority values
assigned) do not cause starvation of low-priority event sources (those
with positive priority values assigned).
The order in which event sources with the same priority are dispatched
is undefined, but the event loop generally tries to dispatch them in
the order it learnt about events on them. As the backing kernel
primitives do not provide accurate information about the order in which
events occurred this is not necessarily reliable. However, it is
guaranteed that if events are seen on multiple same-priority event
sources at the same time, each one is not dispatched again until all
others have been dispatched once. This behavior guarantees that within
each priority particular event sources do not starve or dominate the
event loop.
The priority of event sources may be changed at any time of their
lifetime, with the exception of inotify event sources (i.e. those
created with sd_event_add_inotify(3)) whose priority may only be
changed in the time between their initial creation and the first
subsequent event loop iteration.
sd_event_source_get_priority() may be used to query the current
priority assigned to the event source object source.
RETURN VALUE
On success, sd_event_source_set_priority() and
sd_event_source_get_priority() return a non-negative integer. On
failure, they return a negative errno-style error code.
Errors
Returned errors may indicate the following problems:
-EINVAL
source is not a valid pointer to an sd_event_source object.
-ENOMEM
Not enough memory.
-ESTALE
The event loop is already terminated.
-ECHILD
The event loop has been created in a different process, library or
module instance.
NOTES
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 started.
SEE ALSO
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)
systemd 254 SD_EVENT_SOURCE_SET_PRIORITY(3)
Want to link to this manual page? Use this URL:
<http://star2.abcm.com/cgi-bin/bsdi-man?query=sd_event_source_set_priority&sektion=3&manpath=>