trace: Multi-backend tracing

Adds support to compile QEMU with multiple tracing backends at the same time.

For example, you can compile QEMU with:

  $ ./configure --enable-trace-backends=ftrace,dtrace

Where 'ftrace' can be handy for having an in-flight record of events, and 'dtrace' can be later used to extract more information from the system.

This patch allows having both available without recompiling QEMU.

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

3 files changed, 41 insertions, 41 deletions

diff --git a/scripts/tracetool.py b/scripts/tracetool.py
index 5f4890f..83bde7b 100755
--- a/scripts/tracetool.py
+++ b/scripts/tracetool.py
@@ -6,7 +6,7 @@ Command-line wrapper for the tracetool machinery.
 """
 
 __author__     = "Lluís Vilanova <vilanova@ac.upc.edu>"
-__copyright__  = "Copyright 2012, Lluís Vilanova <vilanova@ac.upc.edu>"
+__copyright__  = "Copyright 2012-2014, Lluís Vilanova <vilanova@ac.upc.edu>"
 __license__    = "GPL version 2 or (at your option) any later version"
 
 __maintainer__ = "Stefan Hajnoczi"
@@ -32,7 +32,7 @@ def error_opt(msg = None):
     format_descr = "\n".join([ "    %-15s %s" % (n, d)
                                for n,d in tracetool.format.get_list() ])
     error_write("""\
-Usage: %(script)s --format=<format> --backend=<backend> [<options>]
+Usage: %(script)s --format=<format> --backends=<backends> [<options>]
 
 Backends:
 %(backends)s
@@ -43,7 +43,7 @@ Formats:
 Options:
     --help                   This help message.
     --list-backends          Print list of available backends.
-    --check-backend          Check if the given backend is valid.
+    --check-backends         Check if the given backend is valid.
     --binary <path>          Full path to QEMU binary.
     --target-type <type>     QEMU emulator target type ('system' or 'user').
     --target-name <name>     QEMU emulator target name.
@@ -65,16 +65,17 @@ def main(args):
     global _SCRIPT
     _SCRIPT = args[0]
 
-    long_opts  = [ "backend=", "format=", "help", "list-backends", "check-backend" ]
-    long_opts += [ "binary=", "target-type=", "target-name=", "probe-prefix=" ]
+    long_opts = ["backends=", "format=", "help", "list-backends",
+                 "check-backends"]
+    long_opts += ["binary=", "target-type=", "target-name=", "probe-prefix="]
 
     try:
         opts, args = getopt.getopt(args[1:], "", long_opts)
     except getopt.GetoptError, err:
         error_opt(str(err))
 
-    check_backend = False
-    arg_backend = ""
+    check_backends = False
+    arg_backends = []
     arg_format = ""
     binary = None
     target_type = None
@@ -84,8 +85,8 @@ def main(args):
         if opt == "--help":
             error_opt()
 
-        elif opt == "--backend":
-            arg_backend = arg
+        elif opt == "--backends":
+            arg_backends = arg.split(",")
         elif opt == "--format":
             arg_format = arg
 
@@ -93,8 +94,8 @@ def main(args):
             public_backends = tracetool.backend.get_list(only_public = True)
             out(", ".join([ b for b,_ in public_backends ]))
             sys.exit(0)
-        elif opt == "--check-backend":
-            check_backend = True
+        elif opt == "--check-backends":
+            check_backends = True
 
         elif opt == "--binary":
             binary = arg
@@ -108,14 +109,14 @@ def main(args):
         else:
             error_opt("unhandled option: %s" % opt)
 
-    if arg_backend is None:
-        error_opt("backend not set")
+    if len(arg_backends) == 0:
+        error_opt("no backends specified")
 
-    if check_backend:
-        if tracetool.backend.exists(arg_backend):
-            sys.exit(0)
-        else:
-            sys.exit(1)
+    if check_backends:
+        for backend in arg_backends:
+            if not tracetool.backend.exists(backend):
+                sys.exit(1)
+        sys.exit(0)
 
     if arg_format == "stap":
         if binary is None:
@@ -126,11 +127,11 @@ def main(args):
             error_opt("--target-name is required for SystemTAP tapset generator")
 
         if probe_prefix is None:
-            probe_prefix = ".".join([ "qemu", target_type, target_name ])
+            probe_prefix = ".".join(["qemu", target_type, target_name])
 
     try:
-        tracetool.generate(sys.stdin, arg_format, arg_backend,
-                           binary = binary, probe_prefix = probe_prefix)
+        tracetool.generate(sys.stdin, arg_format, arg_backends,
+                           binary=binary, probe_prefix=probe_prefix)
     except tracetool.TracetoolError, e:
         error_opt(str(e))
 
diff --git a/scripts/tracetool/__init__.py b/scripts/tracetool/__init__.py
index eccf552..e8e8edc 100644
--- a/scripts/tracetool/__init__.py
+++ b/scripts/tracetool/__init__.py
@@ -233,9 +233,9 @@ def try_import(mod_name, attr_name=None, attr_default=None):
         return False, None
 
 
-def generate(fevents, format, backend,
+def generate(fevents, format, backends,
              binary=None, probe_prefix=None):
-    """Generate the output for the given (format, backend) pair.
+    """Generate the output for the given (format, backends) pair.
 
     Parameters
     ----------
@@ -243,8 +243,8 @@ def generate(fevents, format, backend,
         Event description file.
     format : str
         Output format name.
-    backend : str
-        Output backend name.
+    backends : list
+        Output backend names.
     binary : str or None
         See tracetool.backend.dtrace.BINARY.
     probe_prefix : str or None
@@ -258,15 +258,13 @@ def generate(fevents, format, backend,
         raise TracetoolError("format not set")
     if not tracetool.format.exists(format):
         raise TracetoolError("unknown format: %s" % format)
-    format = format.replace("-", "_")
-
-    backend = str(backend)
-    if len(backend) is 0:
-        raise TracetoolError("backend not set")
-    if not tracetool.backend.exists(backend):
-        raise TracetoolError("unknown backend: %s" % backend)
-    backend = backend.replace("-", "_")
-    backend = tracetool.backend.Wrapper(backend, format)
+
+    if len(backends) is 0:
+        raise TracetoolError("no backends specified")
+    for backend in backends:
+        if not tracetool.backend.exists(backend):
+            raise TracetoolError("unknown backend: %s" % backend)
+    backend = tracetool.backend.Wrapper(backends, format)
 
     import tracetool.backend.dtrace
     tracetool.backend.dtrace.BINARY = binary
diff --git a/scripts/tracetool/backend/__init__.py b/scripts/tracetool/backend/__init__.py
index 5e36f04..5bfa1ef 100644
--- a/scripts/tracetool/backend/__init__.py
+++ b/scripts/tracetool/backend/__init__.py
@@ -99,17 +99,18 @@ def exists(name):
 
 
 class Wrapper:
-    def __init__(self, backend, format):
-        self._backend = backend.replace("-", "_")
+    def __init__(self, backends, format):
+        self._backends = [backend.replace("-", "_") for backend in backends]
         self._format = format.replace("-", "_")
-        assert exists(self._backend)
+        assert all(exists(backend) for backend in self._backends)
         assert tracetool.format.exists(self._format)
 
     def _run_function(self, name, *args, **kwargs):
-        func = tracetool.try_import("tracetool.backend." + self._backend,
-                                    name % self._format, None)[1]
-        if func is not None:
-            func(*args, **kwargs)
+        for backend in self._backends:
+            func = tracetool.try_import("tracetool.backend." + backend,
+                                        name % self._format, None)[1]
+            if func is not None:
+                func(*args, **kwargs)
 
     def generate_begin(self, events):
         self._run_function("generate_%s_begin", events)