Commit 3932ef3f authored by Stefan Hajnoczi's avatar Stefan Hajnoczi
Browse files

trace: add TRACE_<event>_BACKEND_DSTATE() 



QEMU keeps track of trace event enabled/disabled state and provides
monitor commands to inspect and modify the "dstate".  SystemTap and
LTTng UST maintain independent enabled/disabled states for each trace
event, the other backends rely on QEMU dstate.

Introduce a new per-event macro that combines backend-specific dstate
like this:

  #define TRACE_MY_EVENT_BACKEND_DSTATE() ( \
      QEMU_MY_EVENT_ENABLED() || /* SystemTap */ \
      tracepoint_enabled(qemu, my_event) /* LTTng UST */ || \
      false)

This will be used to extend trace_event_get_state() in the next patch.

[Daniel Berrange pointed out that QEMU_MY_EVENT_ENABLED() must be true
by default, not false.  This way events will fire even if the DTrace
implementation does not implement the SystemTap semaphores feature.

Ubuntu Precise uses lttng-ust-dev 2.0.2 which does not have
tracepoint_enabled(), so we need a compatibility wrapper to keep Travis
builds passing.
--Stefan]

Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Message-id: 20170731140718.22010-2-stefanha@redhat.com
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>

fixup! trace: add TRACE_<event>_BACKEND_DSTATE()
parent ea1ff54f

scripts/tracetool/__init__.py

+1 −0
Original line number Diff line number Diff line
@@ -271,6 +271,7 @@ class Event(object): 
    QEMU_TRACE_NOCHECK       = "_nocheck__" + QEMU_TRACE

    QEMU_TRACE_TCG           = QEMU_TRACE + "_tcg"

    QEMU_DSTATE              = "_TRACE_%(NAME)s_DSTATE"

    QEMU_BACKEND_DSTATE      = "TRACE_%(NAME)s_BACKEND_DSTATE"

    QEMU_EVENT               = "_TRACE_%(NAME)s_EVENT"



    def api(self, fmt=None):

scripts/tracetool/backend/__init__.py

+3 −0
Original line number Diff line number Diff line
@@ -119,5 +119,8 @@ class Wrapper: 
    def generate(self, event, group):

        self._run_function("generate_%s", event, group)



    def generate_backend_dstate(self, event, group):

        self._run_function("generate_%s_backend_dstate", event, group)



    def generate_end(self, events, group):

        self._run_function("generate_%s_end", events, group)

scripts/tracetool/backend/dtrace.py

+12 −0
Original line number Diff line number Diff line
@@ -44,8 +44,20 @@ def generate_h_begin(events, group): 
    out('#include "%s"' % header,

        '')



    # SystemTap defines <provider>_<name>_ENABLED() but other DTrace

    # implementations might not.

    for e in events:

        out('#ifndef QEMU_%(uppername)s_ENABLED',

            '#define QEMU_%(uppername)s_ENABLED() true',

            '#endif',

            uppername=e.name.upper())



def generate_h(event, group):

    out('    QEMU_%(uppername)s(%(argnames)s);',

        uppername=event.name.upper(),

        argnames=", ".join(event.args.names()))





def generate_h_backend_dstate(event, group):

    out('    QEMU_%(uppername)s_ENABLED() || \\',

        uppername=event.name.upper())

scripts/tracetool/backend/ftrace.py

+5 −0
Original line number Diff line number Diff line
@@ -45,3 +45,8 @@ def generate_h(event, group): 
        event_id="TRACE_" + event.name.upper(),

        fmt=event.fmt.rstrip("\n"),

        argnames=argnames)





def generate_h_backend_dstate(event, group):

    out('    trace_event_get_state_dynamic_by_id(%(event_id)s) || \\',

        event_id="TRACE_" + event.name.upper())

scripts/tracetool/backend/log.py

+5 −0
Original line number Diff line number Diff line
@@ -48,3 +48,8 @@ def generate_h(event, group): 
        name=event.name,

        fmt=event.fmt.rstrip("\n"),

        argnames=argnames)





def generate_h_backend_dstate(event, group):

    out('    trace_event_get_state_dynamic_by_id(%(event_id)s) || \\',

        event_id="TRACE_" + event.name.upper())