• Tom Zanussi's avatar
    tracing: Add and use generic set_trigger_filter() implementation · bac5fb97
    Tom Zanussi authored
    Add a generic event_command.set_trigger_filter() op implementation and
    have the current set of trigger commands use it - this essentially
    gives them all support for filters.
    
    Syntactically, filters are supported by adding 'if <filter>' just
    after the command, in which case only events matching the filter will
    invoke the trigger.  For example, to add a filter to an
    enable/disable_event command:
    
        echo 'enable_event:system:event if common_pid == 999' > \
                  .../othersys/otherevent/trigger
    
    The above command will only enable the system:event event if the
    common_pid field in the othersys:otherevent event is 999.
    
    As another example, to add a filter to a stacktrace command:
    
        echo 'stacktrace if common_pid == 999' > \
                       .../somesys/someevent/trigger
    
    The above command will only trigger a stacktrace if the common_pid
    field in the event is 999.
    
    The filter syntax is the same as that described in the 'Event
    filtering' section of Documentation/trace/events.txt.
    
    Because triggers can now use filters, the trigger-invoking logic needs
    to be moved in those cases - e.g. for ftrace_raw_event_calls, if a
    trigger has a filter associated with it, the trigger invocation now
    needs to happen after the { assign; } part of the call, in order for
    the trigger condition to be tested.
    
    There's still a SOFT_DISABLED-only check at the top of e.g. the
    ftrace_raw_events function, so when an event is soft disabled but not
    because of the presence of a trigger, the original SOFT_DISABLED
    behavior remains unchanged.
    
    There's also a bit of trickiness in that some triggers need to avoid
    being invoked while an event is currently in the process of being
    logged, since the trigger may itself log data into the trace buffer.
    Thus we make sure the current event is committed before invoking those
    triggers.  To do that, we split the trigger invocation in two - the
    first part (event_triggers_call()) checks the filter using the current
    trace record; if a command has the post_trigger flag set, it sets a
    bit for itself in the return value, otherwise it directly invoks the
    trigger.  Once all commands have been either invoked or set their
    return flag, event_triggers_call() returns.  The current record is
    then either committed or discarded; if any commands have deferred
    their triggers, those commands are finally invoked following the close
    of the current event by event_triggers_post_call().
    
    To simplify the above and make it more efficient, the TRIGGER_COND bit
    is introduced, which is set only if a soft-disabled trigger needs to
    use the log record for filter testing or needs to wait until the
    current log record is closed.
    
    The syscall event invocation code is also changed in analogous ways.
    
    Because event triggers need to be able to create and free filters,
    this also adds a couple external wrappers for the existing
    create_filter and free_filter functions, which are too generic to be
    made extern functions themselves.
    
    Link: http://lkml.kernel.org/r/7164930759d8719ef460357f143d995406e4eead.1382622043.git.tom.zanussi@linux.intel.com
    
    Signed-off-by: default avatarTom Zanussi <tom.zanussi@linux.intel.com>
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    bac5fb97
ftrace_event.h 14.8 KB