-Here, two event rules are created. The first one has a single condition:
-the tracepoint name must match `hello:world`. The second one has two
-conditions:
-
-* The tracepoint name must match `hello:world`, _and_
-* The tracepoint's defined log level must be at least as severe as
- the `TRACE_INFO` level.
-
-In this case, the second event rule is pointless because the first one
-is more general: it does not care about the tracepoint's log level.
-If an event source matching both event rules is reached by the
-application's execution, only one event is emitted.
-
-The available conditions for the Linux kernel domain are:
-
-* Tracepoint/system call name ('EVENT' argument with option:--tracepoint
- or option:--syscall options) or dynamic probe/function name/address
- (option:--probe, option:--userspace-probe, and option:--function
- option's argument) which must match event source's equivalent.
-+
-You can use `*` characters at any place in the tracepoint or system
-call name as wildcards to match zero or more characters. To use a
-literal `*` character, use :escwc:.
-
-* Filter expression (option:--filter option) executed against the
- dynamic values of event fields at execution time that must evaluate
- to true. See the <<filter-expr,Filter expression>> section
- below for more information.
-
-The available conditions for the application domains are:
-
-* Tracepoint name ('EVENT' with option:--tracepoint option) which must
- match event source's equivalent.
-+
-You can use `*` characters at any place in the tracepoint name as
-wildcards to match zero or more characters. To use a literal `*`
-character, use :escwc:. When you create an event rule with a tracepoint
-name containing a wildcard, you can exclude specific tracepoint names
-from the match with the option:--exclude option.
-
-* Filter expression (option:--filter option) executed against the
- dynamic values of event fields at execution time that must evaluate
- to true. See the <<filter-expr,Filter expression>> section
- below for more information.
-* Event's log level that must be at least as severe as a given
- log level (option:--loglevel option) or match exactly a given log
- level (option:--loglevel-only option).
-
-When using `lttng enable-event` with a set of conditions that does not
-currently exist for the chosen tracing session, domain, and channel,
-a new event rule is created. Otherwise, the existing event rule is
-enabled if it is currently disabled
-(see man:lttng-disable-event(1)).
-
-The option:--all option can be used alongside the option:--tracepoint
-or option:--syscall options. When this option is used, no 'EVENT'
-argument must be specified. This option defines a single event rule
-matching _all_ the possible events of a given tracing domain for the
-chosen channel and tracing session. It is the equivalent of an 'EVENT'
-argument named `*` (wildcard).
-
-
-[[filter-expr]]
-Filter expression
-~~~~~~~~~~~~~~~~~
-A filter expression can be specified with the option:--filter option
-when creating a new event rule. If the filter expression evaluates
-to true when executed against the dynamic values of an event's fields
-when tracing, the filtering condition passes.
+* Enable one or more disabled recording event rules.
++
+See the ``<<enable,Enable a disabled recording event rule>>'' section
+below.
+
+See man:lttng-concepts(7) to learn more about instrumentation points,
+events, recording event rules, and event records.
+
+The recording event rule(s) to create or enable belong to:
+
+With the option:--session='SESSION' option::
+ The recording session named 'SESSION'.
+
+Without the option:--session option::
+ The current recording session (see man:lttng-concepts(7) to learn
+ more about the current recording session).
+
+With the option:--channel='CHANNEL' option::
+ The channel named 'CHANNEL'.
+
+Without the option:--channel option::
+ The channel named `channel0`.
++
+If there's already a channel for the selected recording session and
+domain which isn't named `channel0`, the `enable-event` command fails.
+Otherwise, it automatically creates it.
+
+See the ``<<examples,EXAMPLES>>'' section below for usage examples.
+
+List the recording event rules of a specific recording session
+and/or channel with the man:lttng-list(1) and man:lttng-status(1)
+commands.
+
+Disable an enabled recording event rule with the
+man:lttng-disable-event(1) command.
+
+
+Overview of recording event rule conditions
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+For LTTng to emit and record an event{nbsp}__E__,{nbsp}__E__ must
+satisfy *all* the conditions of a recording event rule{nbsp}__ER__, that
+is:
+
+Explicit conditions::
+ You set the following conditions when you create or
+ enable{nbsp}__ER__ with the `enable-event` command:
++
+--
+* The instrumentation point type from which LTTng creates{nbsp}__E__
+ has a specific type.
++
+See the ``<<inst-point-type-cond,Instrumentation point type
+condition>>'' section below.
+
+* A pattern matches the name of{nbsp}__E__ while another pattern
+ doesn't.
++
+See the ``<<event-name-cond,Event name condition>>'' section below.
+
+* The log level of the instrumentation point from which LTTng
+ creates{nbsp}__E__ is at least as severe as some value, or is exactly
+ some value.
++
+See the ``<<inst-point-log-level-cond,Instrumentation point log level
+condition>>'' section below.
+
+* The fields of the payload of{nbsp}__E__ and the current context fields
+ satisfy a filter expression.
++
+See the ``<<filter-cond,Event payload and context filter condition>>''
+section below.
+--
+
+Implicit conditions::
++
+--
+* _ER_ itself is enabled.
++
+A recording event rule is enabled on creation.
++
+Enable a disabled recording event rule with the `enable-event` command.
+
+* The channel to which{nbsp}__ER__ is attached is enabled.
++
+A channel is enabled on creation.
++
+Enable a disabled channel with the man:lttng-enable-channel(1) command.
+
+* The recording session of{nbsp}__ER__ is active (started).
++
+A recording session is inactive (stopped) on creation.
++
+Start an inactive recording session with the man:lttng-start(1) command.
+
+* The process for which LTTng creates{nbsp}__E__ is allowed to record
+ events.
++
+All processes are allowed to record events on recording session
+creation.
++
+Use the man:lttng-track(1) and man:lttng-untrack(1) commands to select
+which processes are allowed to record events based on specific process
+attributes.
+--
+
+The dedicated command-line options of most conditions are optional: if
+you don't specify the option, the associated condition is always
+satisfied.
+
+
+[[inst-point-type-cond]]
+Instrumentation point type condition
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+An event{nbsp}__E__ satisfies the instrumentation point type condition
+of a recording event rule if the instrumentation point from which LTTng
+creates{nbsp}__E__ is:
+
+For the Linux kernel tracing domain (option:--kernel option)::
+ With the option:--tracepoint option or without any other instrumentation point type option:::
+ An LTTng kernel tracepoint, that is, a statically defined point
+ in the source code of the kernel image or of a kernel module
+ with LTTng kernel tracer macros.
++
+As of LTTng{nbsp}{lttng_version}, this is the default instrumentation
+point type of the Linux kernel tracing domain, but this may change in
+the future.
++
+List the available Linux kernel tracepoints with `lttng list --kernel`.
+See man:lttng-list(1) to learn more.
+
+ With the option:--syscall option:::
+ The entry and exit of a Linux kernel system call.
++
+List the available Linux kernel system call instrumentation points with
+`lttng list --kernel --syscall`. See man:lttng-list(1) to learn more.
+
+ With the option:--probe option:::
+ A Linux kprobe, that is, a single probe dynamically placed in
+ the compiled kernel code.
++
+The argument of the option:--probe option is the location of the
+kprobe to insert, either a symbol or a
+memory address, while 'RECORDNAME' is the name of the record
+of{nbsp}__E__ (see the ``<<er-name,Event record name>>'' section below).
++
+The payload of a Linux kprobe event is empty.