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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()
51 lines
1.2 KiB
Python
51 lines
1.2 KiB
Python
#!/usr/bin/env python
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# -*- coding: utf-8 -*-
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"""
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LTTng User Space Tracing backend.
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"""
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__author__ = "Lluís Vilanova <vilanova@ac.upc.edu>"
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__copyright__ = "Copyright 2012-2017, 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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from tracetool import out
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PUBLIC = True
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def generate_h_begin(events, group):
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if group == "root":
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header = "trace-ust-root.h"
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else:
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header = "trace-ust.h"
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out('#include <lttng/tracepoint.h>',
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'#include "%s"' % header,
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'',
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'/* tracepoint_enabled() was introduced in LTTng UST 2.7 */',
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'#ifndef tracepoint_enabled',
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'#define tracepoint_enabled(a, b) true',
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'#endif',
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'')
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def generate_h(event, group):
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argnames = ", ".join(event.args.names())
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if len(event.args) > 0:
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argnames = ", " + argnames
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out(' tracepoint(qemu, %(name)s%(tp_args)s);',
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name=event.name,
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tp_args=argnames)
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def generate_h_backend_dstate(event, group):
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out(' tracepoint_enabled(qemu, %(name)s) || \\',
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name=event.name)
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