lttng-add-context(1)
====================
+:revdate: 5 Februrary 2018
NAME
List the available context fields:
[verse]
-*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *add-context* --list
+*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *add-context* option:--list
DESCRIPTION
The `lttng add-context` command adds one or more context fields to a
channel.
-Channels are created with the linklttng:lttng-enable-channel(1) command.
+Channels are created with the man:lttng-enable-channel(1) command.
When context fields are added to a channel, all the events emitted
within this channel contain the dynamic values of those context fields.
can only be used in the Linux kernel tracing domain, while per-thread
counters can only be used in the user space tracing domain.
+It is also possible to enable PMU counters by raw ID using the
+`perf:cpu:raw:rN:NAME` (Linux kernel tracing domain) or
+`perf:thread:raw:rN:NAME` (user space tracing domain), with:
+
+`N`::
+ A hexadecimal event descriptor which is the same format as used
+ by man:perf-record(1): a concatenation of the event number and umask
+ value provided by the processor's manufacturer. The possible values
+ for this field are processor-specific.
+
+`NAME`::
+ Custom name to easily recognize the counter.
+
Application-specific context fields can be added to a channel using the
following syntax:
Use the option:--list option without other arguments to list the
available context field names.
+See the <<limitations,LIMITATIONS>> section below for a list of
+limitations to consider.
include::common-cmd-options-head.txt[]
Target
~~~~~~
-option:-c, option:--channel='CHANNEL'::
+option:-c 'CHANNEL', option:--channel='CHANNEL'::
Add context fields to a channel named 'CHANNEL' instead of adding
them to all the channels.
-option:-s, option:--session='SESSION'::
+option:-s 'SESSION', option:--session='SESSION'::
Add context fields to a channel in the tracing session named 'SESSION'
instead of the current tracing session.
option:--list::
List the available context fields. Use this option alone.
-option:-t, option:--type='TYPE'::
+option:-t 'TYPE', option:--type='TYPE'::
Add context field named 'TYPE'. This option can be repeated as
many times as needed on the command-line.
include::common-cmd-help-options.txt[]
+[[limitations]]
+LIMITATIONS
+-----------
+As of this version of LTTng, it is not possible to add context fields to
+a channel once its tracing session has been started (see man:lttng-start(1))
+at least once.
include::common-cmd-footer.txt[]
SEE ALSO
--------
-linklttng:lttng(1)
+man:lttng(1)