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>

10 files changed, 76 insertions, 156 deletions

diff --git a/trace/Makefile.objs b/trace/Makefile.objs
index 6a30467..d7a8696 100644
--- a/trace/Makefile.objs
+++ b/trace/Makefile.objs
@@ -3,12 +3,12 @@
 ######################################################################
 # Auto-generated event descriptions for LTTng ust code
 
-ifeq ($(TRACE_BACKEND),ust)
+ifeq ($(findstring ust,$(TRACE_BACKENDS)),ust)
 $(obj)/generated-ust-provider.h: $(obj)/generated-ust-provider.h-timestamp
 $(obj)/generated-ust-provider.h-timestamp: $(SRC_PATH)/trace-events
 	$(call quiet-command,$(TRACETOOL) \
 		--format=ust-events-h \
-		--backend=$(TRACE_BACKEND) \
+		--backends=$(TRACE_BACKENDS) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
 	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
 
@@ -16,7 +16,7 @@ $(obj)/generated-ust.c: $(obj)/generated-ust.c-timestamp $(BUILD_DIR)/config-hos
 $(obj)/generated-ust.c-timestamp: $(SRC_PATH)/trace-events
 	$(call quiet-command,$(TRACETOOL) \
 		--format=ust-events-c \
-		--backend=$(TRACE_BACKEND) \
+		--backends=$(TRACE_BACKENDS) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
 	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
 
@@ -31,7 +31,7 @@ $(obj)/generated-events.h: $(obj)/generated-events.h-timestamp
 $(obj)/generated-events.h-timestamp: $(SRC_PATH)/trace-events
 	$(call quiet-command,$(TRACETOOL) \
 		--format=events-h \
-		--backend=$(TRACE_BACKEND) \
+		--backends=$(TRACE_BACKENDS) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
 	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
 
@@ -39,7 +39,7 @@ $(obj)/generated-events.c: $(obj)/generated-events.c-timestamp $(BUILD_DIR)/conf
 $(obj)/generated-events.c-timestamp: $(SRC_PATH)/trace-events
 	$(call quiet-command,$(TRACETOOL) \
 		--format=events-c \
-		--backend=$(TRACE_BACKEND) \
+		--backends=$(TRACE_BACKENDS) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
 	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
 
@@ -54,23 +54,21 @@ $(obj)/generated-tracers.h: $(obj)/generated-tracers.h-timestamp
 $(obj)/generated-tracers.h-timestamp: $(SRC_PATH)/trace-events $(BUILD_DIR)/config-host.mak
 	$(call quiet-command,$(TRACETOOL) \
 		--format=h \
-		--backend=$(TRACE_BACKEND) \
+		--backends=$(TRACE_BACKENDS) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
 
 ######################################################################
 # Auto-generated tracing routines (non-DTrace)
 
-ifneq ($(TRACE_BACKEND),dtrace)
 $(obj)/generated-tracers.c: $(obj)/generated-tracers.c-timestamp
 	@cmp -s $< $@ || cp $< $@
 $(obj)/generated-tracers.c-timestamp: $(SRC_PATH)/trace-events $(BUILD_DIR)/config-host.mak
 	$(call quiet-command,$(TRACETOOL) \
 		--format=c \
-		--backend=$(TRACE_BACKEND) \
+		--backends=$(TRACE_BACKENDS) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
 
 $(obj)/generated-tracers.o: $(obj)/generated-tracers.c $(obj)/generated-tracers.h
-endif
 
 
 ######################################################################
@@ -79,27 +77,27 @@ endif
 # Normal practice is to name DTrace probe file with a '.d' extension
 # but that gets picked up by QEMU's Makefile as an external dependency
 # rule file. So we use '.dtrace' instead
-ifeq ($(TRACE_BACKEND),dtrace)
-$(obj)/generated-tracers.dtrace: $(obj)/generated-tracers.dtrace-timestamp
-$(obj)/generated-tracers.dtrace-timestamp: $(SRC_PATH)/trace-events $(BUILD_DIR)/config-host.mak
+ifeq ($(findstring dtrace,$(TRACE_BACKENDS)),dtrace)
+$(obj)/generated-tracers-dtrace.dtrace: $(obj)/generated-tracers-dtrace.dtrace-timestamp
+$(obj)/generated-tracers-dtrace.dtrace-timestamp: $(SRC_PATH)/trace-events $(BUILD_DIR)/config-host.mak
 	$(call quiet-command,$(TRACETOOL) \
 		--format=d \
-		--backend=$(TRACE_BACKEND) \
+		--backends=$(TRACE_BACKENDS) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
 	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
 
-$(obj)/generated-tracers-dtrace.h: $(obj)/generated-tracers.dtrace
+$(obj)/generated-tracers-dtrace.h: $(obj)/generated-tracers-dtrace.dtrace
 	$(call quiet-command,dtrace -o $@ -h -s $<, "  GEN   $@")
 
-$(obj)/generated-tracers.o: $(obj)/generated-tracers.dtrace
+$(obj)/generated-tracers-dtrace.o: $(obj)/generated-tracers-dtrace.dtrace
+
+util-obj-y += generated-tracers-dtrace.o
 endif
 
 ######################################################################
 # Backend code
 
-util-obj-$(CONFIG_TRACE_DEFAULT) += default.o
 util-obj-$(CONFIG_TRACE_SIMPLE) += simple.o
-util-obj-$(CONFIG_TRACE_STDERR) += stderr.o
 util-obj-$(CONFIG_TRACE_FTRACE) += ftrace.o
 util-obj-$(CONFIG_TRACE_UST) += generated-ust.o
 util-obj-y += control.o
diff --git a/trace/control-internal.h b/trace/control-internal.h
index b3f587e..5a8df28 100644
--- a/trace/control-internal.h
+++ b/trace/control-internal.h
@@ -1,7 +1,7 @@
 /*
  * Interface for configuring and controlling the state of tracing events.
  *
- * Copyright (C) 2011-2012 Lluís Vilanova <vilanova@ac.upc.edu>
+ * Copyright (C) 2011-2014 Lluís Vilanova <vilanova@ac.upc.edu>
  *
  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  * See the COPYING file in the top-level directory.
@@ -61,7 +61,7 @@ static inline void trace_event_set_state_dynamic(TraceEvent *ev, bool state)
 {
     assert(ev != NULL);
     assert(trace_event_get_state_static(ev));
-    return trace_event_set_state_dynamic_backend(ev, state);
+    ev->dstate = state;
 }
 
 #endif  /* TRACE__CONTROL_INTERNAL_H */
diff --git a/trace/control.c b/trace/control.c
index 4aa02cf..45e6604 100644
--- a/trace/control.c
+++ b/trace/control.c
@@ -1,13 +1,19 @@
 /*
  * Interface for configuring and controlling the state of tracing events.
  *
- * Copyright (C) 2011-2012 Lluís Vilanova <vilanova@ac.upc.edu>
+ * Copyright (C) 2011-2014 Lluís Vilanova <vilanova@ac.upc.edu>
  *
  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  * See the COPYING file in the top-level directory.
  */
 
 #include "trace/control.h"
+#ifdef CONFIG_TRACE_SIMPLE
+#include "trace/simple.h"
+#endif
+#ifdef CONFIG_TRACE_FTRACE
+#include "trace/ftrace.h"
+#endif
 
 
 TraceEvent *trace_event_name(const char *name)
@@ -79,7 +85,20 @@ TraceEvent *trace_event_pattern(const char *pat, TraceEvent *ev)
     return NULL;
 }
 
-void trace_backend_init_events(const char *fname)
+void trace_print_events(FILE *stream, fprintf_function stream_printf)
+{
+    TraceEventID i;
+
+    for (i = 0; i < trace_event_count(); i++) {
+        TraceEvent *ev = trace_event_id(i);
+        stream_printf(stream, "%s [Event ID %u] : state %u\n",
+                      trace_event_get_name(ev), i,
+                      trace_event_get_state_static(ev) &&
+                      trace_event_get_state_dynamic(ev));
+    }
+}
+
+static void trace_init_events(const char *fname)
 {
     if (fname == NULL) {
         return;
@@ -130,3 +149,29 @@ void trace_backend_init_events(const char *fname)
         exit(1);
     }
 }
+
+bool trace_init_backends(const char *events, const char *file)
+{
+#ifdef CONFIG_TRACE_SIMPLE
+    if (!st_init(file)) {
+        fprintf(stderr, "failed to initialize simple tracing backend.\n");
+        return false;
+    }
+#else
+    if (file) {
+        fprintf(stderr, "error: -trace file=...: "
+                "option not supported by the selected tracing backends\n");
+        return false;
+    }
+#endif
+
+#ifdef CONFIG_TRACE_FTRACE
+    if (!ftrace_init()) {
+        fprintf(stderr, "failed to initialize ftrace backend.\n");
+        return false;
+    }
+#endif
+
+    trace_init_events(events);
+    return true;
+}
diff --git a/trace/control.h b/trace/control.h
index cde8260..e1ec033 100644
--- a/trace/control.h
+++ b/trace/control.h
@@ -1,7 +1,7 @@
 /*
  * Interface for configuring and controlling the state of tracing events.
  *
- * Copyright (C) 2011-2012 Lluís Vilanova <vilanova@ac.upc.edu>
+ * Copyright (C) 2011-2014 Lluís Vilanova <vilanova@ac.upc.edu>
  *
  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  * See the COPYING file in the top-level directory.
@@ -146,26 +146,17 @@ static bool trace_event_get_state_dynamic(TraceEvent *ev);
  */
 static void trace_event_set_state_dynamic(TraceEvent *ev, bool state);
 
-/**
- * trace_event_set_state_dynamic_backend:
- *
- * Warning: This function must be implemented by each tracing backend.
- */
-void trace_event_set_state_dynamic_backend(TraceEvent *ev, bool state);
-
 
 
 /**
  * trace_print_events:
  *
  * Print the state of all events.
- *
- * Warning: This function must be implemented by each tracing backend.
  */
 void trace_print_events(FILE *stream, fprintf_function stream_printf);
 
 /**
- * trace_backend_init:
+ * trace_init_backends:
  * @events: Name of file with events to be enabled at startup; may be NULL.
  *          Corresponds to commandline option "-trace events=...".
  * @file:   Name of trace output file; may be NULL.
@@ -173,19 +164,9 @@ void trace_print_events(FILE *stream, fprintf_function stream_printf);
  *
  * Initialize the tracing backend.
  *
- * Warning: This function must be implemented by each tracing backend.
- *
- * Returns: Whether the backend could be successfully initialized.
- */
-bool trace_backend_init(const char *events, const char *file);
-
-/**
- * trace_backend_init_events:
- * @fname: Name of file with events to enable; may be NULL.
- *
- * Generic function to initialize the state of events.
+ * Returns: Whether the backends could be successfully initialized.
  */
-void trace_backend_init_events(const char *fname);
+bool trace_init_backends(const char *events, const char *file);
 
 
 #include "trace/control-internal.h"
diff --git a/trace/default.c b/trace/default.c
deleted file mode 100644
index 6e07a47..0000000
--- a/trace/default.c
+++ /dev/null
@@ -1,40 +0,0 @@
-/*
- * Default implementation for backend initialization from commandline.
- *
- * Copyright (C) 2011-2012 Lluís Vilanova <vilanova@ac.upc.edu>
- *
- * This work is licensed under the terms of the GNU GPL, version 2.  See
- * the COPYING file in the top-level directory.
- */
-
-#include "trace/control.h"
-
-
-void trace_print_events(FILE *stream, fprintf_function stream_printf)
-{
-    fprintf(stderr, "warning: "
-            "cannot print the trace events with the current backend\n");
-    stream_printf(stream, "error: "
-                  "operation not supported with the current backend\n");
-}
-
-void trace_event_set_state_dynamic_backend(TraceEvent *ev, bool state)
-{
-    fprintf(stderr, "warning: "
-            "cannot set the state of a trace event with the current backend\n");
-}
-
-bool trace_backend_init(const char *events, const char *file)
-{
-    if (events) {
-        fprintf(stderr, "error: -trace events=...: "
-                "option not supported by the selected tracing backend\n");
-        return false;
-    }
-    if (file) {
-        fprintf(stderr, "error: -trace file=...: "
-                "option not supported by the selected tracing backend\n");
-        return false;
-    }
-    return true;
-}
diff --git a/trace/ftrace.c b/trace/ftrace.c
index 46b7fdb..a7ae371 100644
--- a/trace/ftrace.c
+++ b/trace/ftrace.c
@@ -42,35 +42,13 @@ static int find_debugfs(char *debugfs)
     return 1;
 }
 
-void trace_print_events(FILE *stream, fprintf_function stream_printf)
-{
-    TraceEventID i;
-
-    for (i = 0; i < trace_event_count(); i++) {
-        TraceEvent *ev = trace_event_id(i);
-        stream_printf(stream, "%s [Event ID %u] : state %u\n",
-                      trace_event_get_name(ev), i, trace_event_get_state_dynamic(ev));
-    }
-}
-
-void trace_event_set_state_dynamic_backend(TraceEvent *ev, bool state)
-{
-    ev->dstate = state;
-}
-
-bool trace_backend_init(const char *events, const char *file)
+bool ftrace_init(void)
 {
     char debugfs[PATH_MAX];
     char path[PATH_MAX];
     int debugfs_found;
     int trace_fd = -1;
 
-    if (file) {
-        fprintf(stderr, "error: -trace file=...: "
-                "option not supported by the selected tracing backend\n");
-        return false;
-    }
-
     debugfs_found = find_debugfs(debugfs);
     if (debugfs_found) {
         snprintf(path, PATH_MAX, "%s/tracing/tracing_on", debugfs);
@@ -97,6 +75,5 @@ bool trace_backend_init(const char *events, const char *file)
         return false;
     }
 
-    trace_backend_init_events(events);
     return true;
 }
diff --git a/trace/ftrace.h b/trace/ftrace.h
index 94cb8d5..863e052 100644
--- a/trace/ftrace.h
+++ b/trace/ftrace.h
@@ -1,10 +1,15 @@
 #ifndef TRACE_FTRACE_H
 #define TRACE_FTRACE_H
 
+#include <stdbool.h>
+
+
 #define MAX_TRACE_STRLEN 512
 #define _STR(x) #x
 #define STR(x) _STR(x)
 
 extern int trace_marker_fd;
 
+bool ftrace_init(void);
+
 #endif /* ! TRACE_FTRACE_H */
diff --git a/trace/simple.c b/trace/simple.c
index 5a2e188..a8f923c 100644
--- a/trace/simple.c
+++ b/trace/simple.c
@@ -368,22 +368,6 @@ void st_flush_trace_buffer(void)
     flush_trace_file(true);
 }
 
-void trace_print_events(FILE *stream, fprintf_function stream_printf)
-{
-    unsigned int i;
-
-    for (i = 0; i < trace_event_count(); i++) {
-        TraceEvent *ev = trace_event_id(i);
-        stream_printf(stream, "%s [Event ID %u] : state %u\n",
-                      trace_event_get_name(ev), i, trace_event_get_state_dynamic(ev));
-    }
-}
-
-void trace_event_set_state_dynamic_backend(TraceEvent *ev, bool state)
-{
-    ev->dstate = state;
-}
-
 /* Helper function to create a thread with signals blocked.  Use glib's
  * portable threads since QEMU abstractions cannot be used due to reentrancy in
  * the tracer.  Also note the signal masking on POSIX hosts so that the thread
@@ -412,7 +396,7 @@ static GThread *trace_thread_create(GThreadFunc fn)
     return thread;
 }
 
-bool trace_backend_init(const char *events, const char *file)
+bool st_init(const char *file)
 {
     GThread *thread;
 
@@ -430,7 +414,6 @@ bool trace_backend_init(const char *events, const char *file)
     }
 
     atexit(st_flush_trace_buffer);
-    trace_backend_init_events(events);
     st_set_trace_file(file);
     return true;
 }
diff --git a/trace/simple.h b/trace/simple.h
index 5260d9a..6997996 100644
--- a/trace/simple.h
+++ b/trace/simple.h
@@ -21,6 +21,7 @@
 void st_print_trace_file_status(FILE *stream, fprintf_function stream_printf);
 void st_set_trace_file_enabled(bool enable);
 bool st_set_trace_file(const char *file);
+bool st_init(const char *file);
 void st_flush_trace_buffer(void);
 
 typedef struct {
diff --git a/trace/stderr.c b/trace/stderr.c
deleted file mode 100644
index e212efd..0000000
--- a/trace/stderr.c
+++ /dev/null
@@ -1,30 +0,0 @@
-#include "trace.h"
-#include "trace/control.h"
-
-
-void trace_print_events(FILE *stream, fprintf_function stream_printf)
-{
-    TraceEventID i;
-
-    for (i = 0; i < trace_event_count(); i++) {
-        TraceEvent *ev = trace_event_id(i);
-        stream_printf(stream, "%s [Event ID %u] : state %u\n",
-                      trace_event_get_name(ev), i, trace_event_get_state_dynamic(ev));
-    }
-}
-
-void trace_event_set_state_dynamic_backend(TraceEvent *ev, bool state)
-{
-    ev->dstate = state;
-}
-
-bool trace_backend_init(const char *events, const char *file)
-{
-    if (file) {
-        fprintf(stderr, "error: -trace file=...: "
-                "option not supported by the selected tracing backend\n");
-        return false;
-    }
-    trace_backend_init_events(events);
-    return true;
-}