[Qemu-devel] [PATCH v3 2/6] trace: Provide a detailed event control interface

[Lluís Vilanova]

This interface decouples event obtention from interaction.

Event can be obtained through three different methods:

* identifier
* name
* simple wildcard pattern

Signed-off-by: Lluís Vilanova <address@hidden>
---
 docs/tracing.txt         |   41 +++++--------
 trace/control-internal.h |   60 +++++++++++++++++++
 trace/control.c          |   92 ++++++++++++++++++++++++++---
 trace/control.h          |  148 ++++++++++++++++++++++++++++++++++++++++++----
 4 files changed, 296 insertions(+), 45 deletions(-)
 create mode 100644 trace/control-internal.h

diff --git a/docs/tracing.txt b/docs/tracing.txt
index a92716f..17690f1 100644
--- a/docs/tracing.txt
+++ b/docs/tracing.txt
@@ -100,44 +100,32 @@ respectively.  This ensures portability between 32- and 
64-bit platforms.
 
 == Generic interface and monitor commands ==
 
-You can programmatically query and control the dynamic state of trace events
-through a backend-agnostic interface:
+You can programmatically query and control the state of trace events through a
+backend-agnostic interface provided by the file "trace/control.h".
 
-* trace_print_events
+Note that some of the backends do not provide an implementation for some parts
+of this interface, in which case QEMU will just print a warning (please refer 
to
+header "trace/control.h" to see which routines are backend-dependant).
 
-* trace_event_set_state
-  Enables or disables trace events at runtime inside QEMU.
-  The function returns "true" if the state of the event has been successfully
-  changed, or "false" otherwise:
-
-    #include "trace/control.h"
-    
-    trace_event_set_state("virtio_irq", true); /* enable */
-    [...]
-    trace_event_set_state("virtio_irq", false); /* disable */
-
-Note that some of the backends do not provide an implementation for this
-interface, in which case QEMU will just print a warning.
-
-This functionality is also provided through monitor commands:
+The state of events can also be queried and modified through monitor commands:
 
 * info trace-events
   View available trace events and their state.  State 1 means enabled, state 0
   means disabled.
 
 * trace-event NAME on|off
-  Enable/disable a given trace event or a group of events having common prefix
-  through wildcard.
+  Enable/disable a given trace event or a group of events (using wildcards).
 
 The "-trace events=<file>" command line argument can be used to enable the
 events listed in <file> from the very beginning of the program. This file must
 contain one event name per line.
 
-A basic wildcard matching is supported in both the monitor command "trace
--event" and the events list file. That means you can enable/disable the events
-having a common prefix in a batch. For example, virtio-blk trace events could
-be enabled using:
-  trace-event virtio_blk_* on
+Wildcard matching is supported in both the monitor command "trace -event" and
+the events list file. That means you can enable/disable the events having a
+common prefix in a batch. For example, virtio-blk trace events could be enabled
+using the following monitor command:
+
+    trace-event virtio_blk_* on
 
 == Trace backends ==
 
@@ -268,3 +256,6 @@ guard such computations and avoid its compilation when the 
event is disabled:
         }
         return ptr;
     }
+
+You can check both if the event has been disabled and is dynamically enabled at
+the same time using the 'trace_event_get_state' routine.
diff --git a/trace/control-internal.h b/trace/control-internal.h
new file mode 100644
index 0000000..81db761
--- /dev/null
+++ b/trace/control-internal.h
@@ -0,0 +1,60 @@
+/*
+ * Interface for configuring and controlling the state of tracing events.
+ *
+ * Copyright (C) 2011, 2012 Lluís Vilanova <address@hidden>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+
+extern TraceEvent trace_events[];
+
+
+static inline TraceEvent *trace_event_id(TraceEventID id)
+{
+    assert(id < trace_event_count());
+    return &trace_events[id];
+}
+
+static inline TraceEventID trace_event_count(void)
+{
+    return TRACE_EVENT_COUNT;
+}
+
+static inline bool trace_event_is_pattern(const char *str)
+{
+    assert(str != NULL);
+
+    while (*str != '\0') {
+        if (*str == '*') {
+            return true;
+        }
+        str++;
+    }
+    return false;
+}
+
+static inline TraceEventID trace_event_get_id(TraceEvent *ev)
+{
+    assert(ev != NULL);
+    return ev->id;
+}
+
+static inline const char * trace_event_get_name(TraceEvent *ev)
+{
+    assert(ev != NULL);
+    return ev->name;
+}
+
+static inline bool trace_event_get_state_static(TraceEvent *ev)
+{
+    assert(ev != NULL);
+    return ev->sstate;
+}
+
+static inline bool trace_event_get_state_dynamic(TraceEvent *ev)
+{
+    assert(ev != NULL);
+    return ev->dstate;
+}
diff --git a/trace/control.c b/trace/control.c
index 4c5527d..7fbe854 100644
--- a/trace/control.c
+++ b/trace/control.c
@@ -1,15 +1,84 @@
 /*
  * Interface for configuring and controlling the state of tracing events.
  *
- * Copyright (C) 2011 Lluís Vilanova <address@hidden>
+ * Copyright (C) 2011, 2012 Lluís Vilanova <address@hidden>
  *
- * This work is licensed under the terms of the GNU GPL, version 2.  See
- * the COPYING file in the top-level directory.
+ * 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"
 
 
+TraceEvent *trace_event_name(const char *name)
+{
+    assert(name != NULL);
+
+    TraceEventID i;
+    for (i = 0; i < trace_event_count(); i++) {
+        TraceEvent *ev = trace_event_id(i);
+        if (strcmp(trace_event_get_name(ev), name) == 0) {
+            return ev;
+        }
+    }
+    return NULL;
+}
+
+static inline bool glob(const char *pat, const char *ev)
+{
+    while (*pat != '\0' && *ev != '\0') {
+        if (*pat == *ev) {
+            pat++;
+            ev++;
+        }
+        else if (*pat == '*') {
+            if (glob(pat, ev+1)) {
+                return true;
+            } else if (glob(pat+1, ev)) {
+                return true;
+            } else {
+                return false;
+            }
+        } else {
+            return false;
+        }
+    }
+
+    while (*pat == '*') {
+        pat++;
+    }
+
+    if (*pat == '\0' && *ev == '\0') {
+        return true;
+    } else {
+        return false;
+    }
+}
+
+TraceEvent *trace_event_pattern(const char *pat, TraceEvent *ev)
+{
+    assert(pat != NULL);
+
+    TraceEventID i;
+
+    if (ev == NULL) {
+        i = -1;
+    } else {
+        i = trace_event_get_id(ev);
+    }
+    i++;
+
+    while (i < trace_event_count()) {
+        TraceEvent *res = trace_event_id(i);
+        if (glob(pat, trace_event_get_name(res))) {
+            return res;
+        }
+        i++;
+    }
+
+    return NULL;
+}
+
 void trace_backend_init_events(const char *fname)
 {
     if (fname == NULL) {
@@ -27,10 +96,19 @@ void trace_backend_init_events(const char *fname)
         size_t len = strlen(line_buf);
         if (len > 1) {              /* skip empty lines */
             line_buf[len - 1] = '\0';
-            if (!trace_event_set_state(line_buf, true)) {
-                fprintf(stderr,
-                        "error: trace event '%s' does not exist\n", line_buf);
-                exit(1);
+            if (trace_event_is_pattern(line_buf)) {
+                TraceEvent *ev;
+                while ((ev = trace_event_pattern(line_buf, ev)) != NULL) {
+                    trace_event_set_state_dynamic(ev, true);
+                }
+            } else {
+                TraceEvent *ev = trace_event_name(line_buf);
+                if (ev == NULL) {
+                    fprintf(stderr,
+                            "error: trace event '%s' does not exist\n", 
line_buf);
+                    exit(1);
+                }
+                trace_event_set_state_dynamic(ev, true);
             }
         }
     }
diff --git a/trace/control.h b/trace/control.h
index 2acaa42..3b9c6f5 100644
--- a/trace/control.h
+++ b/trace/control.h
@@ -1,41 +1,163 @@
 /*
  * Interface for configuring and controlling the state of tracing events.
  *
- * Copyright (C) 2011 Lluís Vilanova <address@hidden>
+ * Copyright (C) 2011, 2012 Lluís Vilanova <address@hidden>
  *
- * This work is licensed under the terms of the GNU GPL, version 2.  See
- * the COPYING file in the top-level directory.
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
  */
 
-#ifndef TRACE_CONTROL_H
-#define TRACE_CONTROL_H
+#ifndef TRACE__CONTROL_H
+#define TRACE__CONTROL_H
 
 #include "qemu-common.h"
+#include "trace-events.h"
 
 
-/** Print the state of all events. */
-void trace_print_events(FILE *stream, fprintf_function stream_printf);
-/** Set the state of an event.
+/**
+ * Opaque generic description of a tracing event.
+ */
+struct TraceEvent;
+typedef struct TraceEvent TraceEvent;
+
+/**
+ * TraceEventID - Unique tracing event identifier.
+ *
+ * These are named as 'TRACE_${EVENT_NAME}'.
+ *
+ * See also: trace-events.h
+ */
+
+/**
+ * Get an event by its identifier.
+ *
+ * @id Event identifier.
+ *
+ * @return Pointer to event.
+ *
+ * @pre The identifier is valid.
+ */
+static TraceEvent *trace_event_id(TraceEventID id);
+
+/**
+ * Search an event by its name.
+ *
+ * @id Event name.
+ *
+ * @return Pointer to Event or NULL if not found.
+ */
+TraceEvent *trace_event_name(const char *name);
+
+/**
+ * Get all events with a given name pattern.
+ *
+ * @pat Event name pattern.
+ * @ev  Event to start searching from.
+ *
+ * @return Pointer to Event or NULL if not found.
+ */
+TraceEvent *trace_event_pattern(const char *pat, TraceEvent *ev);
+
+/**
+ * Whether the given string is an event name pattern.
+ */
+static bool trace_event_is_pattern(const char *str);
+
+/**
+ * Return the number of events.
+ */
+static TraceEventID trace_event_count(void);
+
+
+
+/**
+ * Get the identifier of an event.
+ */
+static TraceEventID trace_event_get_id(TraceEvent *ev);
+
+/**
+ * Get the name of an event.
+ */
+static const char * trace_event_get_name(TraceEvent *ev);
+
+/**
+ * Get the tracing state of an event (both static and dynamic).
+ *
+ * @id Event identifier.
+ *
+ * If the event has the disabled property, the check will have no performance
+ * impact.
+ *
+ * As a down side, you must always use an immediate TraceEventID value.
+ */
+#define trace_event_get_state(id)                       \
+    ((id ##_ENABLED) && trace_event_get_state_dynamic(trace_event_id(id)))
+
+/**
+ * Get the static tracing state of an event.
+ *
+ * @id Event identifier.
+ *
+ * Use the define 'TRACE_${EVENT_NAME}_ENABLED' for compile-time checks (it 
will
+ * be set to 1 or 0 according to the presence of the disabled property).
+ */
+static bool trace_event_get_state_static(TraceEvent *ev);
+
+/**
+ * Get the dynamic tracing state of an event.
+ */
+static bool trace_event_get_state_dynamic(TraceEvent *ev);
+
+/**
+ * Set the tracing state of an event.
+ */
+#define trace_event_set_state(id, state)                \
+    do {                                                \
+        if ((id ##_ENABLED)) {                          \
+            TraceEvent *_e = trace_event_id(id);        \
+            trace_event_set_state_dynamic(_e, state);   \
+        }                                               \
+    } while (0)
+
+/**
+ * Set the dynamic tracing state of an event.
  *
- * @return Whether the state changed.
+ * @warning This function must be implemented by each tracing backend.
  */
-bool trace_event_set_state(const char *name, bool state);
+void trace_event_set_state_dynamic(TraceEvent *ev, bool state);
 
 
-/** Initialize the tracing backend.
+
+/**
+ * Print the state of all events.
+ *
+ * @warning This function must be implemented by each tracing backend.
+ *
+ * @todo Should this be moved to generic code?
+ */
+void trace_print_events(FILE *stream, fprintf_function stream_printf);
+
+/**
+ * Initialize the tracing backend.
  *
  * @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.
  *         Corresponds to commandline option "-trace file=...".
  * @return Whether the backend could be successfully initialized.
+ *
+ * @warning This function must be implemented by each tracing backend.
  */
 bool trace_backend_init(const char *events, const char *file);
 
-/** Generic function to initialize the state of events.
+/**
+ * Generic function to initialize the state of events.
  *
  * @fname Name of file with events to enable; may be NULL.
  */
 void trace_backend_init_events(const char *fname);
 
-#endif  /* TRACE_CONTROL_H */
+
+#include "trace/control-internal.h"
+
+#endif  /* TRACE__CONTROL_H */