3932ef3ffb
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: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20170731140718.22010-2-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
fixup! trace: add TRACE_<event>_BACKEND_DSTATE()
127 lines
4 KiB
Python
127 lines
4 KiB
Python
#!/usr/bin/env python
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# -*- coding: utf-8 -*-
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"""
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Backend management.
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Creating new backends
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---------------------
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A new backend named 'foo-bar' corresponds to Python module
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'tracetool/backend/foo_bar.py'.
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A backend module should provide a docstring, whose first non-empty line will be
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considered its short description.
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All backends must generate their contents through the 'tracetool.out' routine.
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Backend attributes
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------------------
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========= ====================================================================
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Attribute Description
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========= ====================================================================
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PUBLIC If exists and is set to 'True', the backend is considered "public".
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========= ====================================================================
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Backend functions
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-----------------
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All the following functions are optional, and no output will be generated if
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they do not exist.
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=============================== ==============================================
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Function Description
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=============================== ==============================================
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generate_<format>_begin(events) Generate backend- and format-specific file
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header contents.
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generate_<format>_end(events) Generate backend- and format-specific file
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footer contents.
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generate_<format>(event) Generate backend- and format-specific contents
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for the given event.
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=============================== ==============================================
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"""
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__author__ = "Lluís Vilanova <vilanova@ac.upc.edu>"
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__copyright__ = "Copyright 2012-2014, Lluís Vilanova <vilanova@ac.upc.edu>"
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__license__ = "GPL version 2 or (at your option) any later version"
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__maintainer__ = "Stefan Hajnoczi"
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__email__ = "stefanha@linux.vnet.ibm.com"
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import os
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import tracetool
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def get_list(only_public = False):
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"""Get a list of (name, description) pairs."""
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res = [("nop", "Tracing disabled.")]
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modnames = []
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for filename in os.listdir(tracetool.backend.__path__[0]):
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if filename.endswith('.py') and filename != '__init__.py':
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modnames.append(filename.rsplit('.', 1)[0])
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for modname in sorted(modnames):
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module = tracetool.try_import("tracetool.backend." + modname)
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# just in case; should never fail unless non-module files are put there
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if not module[0]:
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continue
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module = module[1]
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public = getattr(module, "PUBLIC", False)
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if only_public and not public:
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continue
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doc = module.__doc__
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if doc is None:
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doc = ""
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doc = doc.strip().split("\n")[0]
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name = modname.replace("_", "-")
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res.append((name, doc))
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return res
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def exists(name):
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"""Return whether the given backend exists."""
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if len(name) == 0:
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return False
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if name == "nop":
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return True
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name = name.replace("-", "_")
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return tracetool.try_import("tracetool.backend." + name)[1]
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class Wrapper:
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def __init__(self, backends, format):
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self._backends = [backend.replace("-", "_") for backend in backends]
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self._format = format.replace("-", "_")
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for backend in self._backends:
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assert exists(backend)
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assert tracetool.format.exists(self._format)
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def _run_function(self, name, *args, **kwargs):
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for backend in self._backends:
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func = tracetool.try_import("tracetool.backend." + backend,
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name % self._format, None)[1]
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if func is not None:
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func(*args, **kwargs)
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def generate_begin(self, events, group):
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self._run_function("generate_%s_begin", events, group)
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def generate(self, event, group):
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self._run_function("generate_%s", event, group)
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def generate_backend_dstate(self, event, group):
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self._run_function("generate_%s_backend_dstate", event, group)
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def generate_end(self, events, group):
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self._run_function("generate_%s_end", events, group)
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