[Qemu-devel] [PATCH v6 13/20] trace: provide mechanism for registering trace events

["Daniel P. Berrange" <berrange@redhat.com>]

Remove the notion of there being a single global array
of trace events, by introducing a method for registering
groups of events.

The module_call_init() needs to be invoked at the start
of any program that wants to make use of the trace
support. Currently this covers system emulators qemu-nbd,
qemu-img and qemu-io.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Lluís Vilanova <vilanova@ac.upc.edu>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---
 include/qemu/module.h                |  2 ++
 qemu-img.c                           |  1 +
 qemu-io.c                            |  1 +
 qemu-nbd.c                           |  1 +
 scripts/tracetool/format/events_c.py |  6 ++++++
 trace/control-internal.h             |  4 +++-
 trace/control.c                      | 25 +++++++++++++++++++++++--
 trace/control.h                      |  1 +
 vl.c                                 |  2 ++
 9 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/include/qemu/module.h b/include/qemu/module.h
index dc2c9d4..877cca7 100644
--- a/include/qemu/module.h
+++ b/include/qemu/module.h
@@ -44,6 +44,7 @@ typedef enum {
     MODULE_INIT_OPTS,
     MODULE_INIT_QAPI,
     MODULE_INIT_QOM,
+    MODULE_INIT_TRACE,
     MODULE_INIT_MAX
 } module_init_type;
 
@@ -51,6 +52,7 @@ typedef enum {
 #define opts_init(function) module_init(function, MODULE_INIT_OPTS)
 #define qapi_init(function) module_init(function, MODULE_INIT_QAPI)
 #define type_init(function) module_init(function, MODULE_INIT_QOM)
+#define trace_init(function) module_init(function, MODULE_INIT_TRACE)
 
 #define block_module_load_one(lib) module_load_one("block-", lib)
 
diff --git a/qemu-img.c b/qemu-img.c
index ceffefe..02c07b9 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -4165,6 +4165,7 @@ int main(int argc, char **argv)
     signal(SIGPIPE, SIG_IGN);
 #endif
 
+    module_call_init(MODULE_INIT_TRACE);
     error_set_progname(argv[0]);
     qemu_init_exec_dir(argv[0]);
 
diff --git a/qemu-io.c b/qemu-io.c
index db129ea..23a229f 100644
--- a/qemu-io.c
+++ b/qemu-io.c
@@ -467,6 +467,7 @@ int main(int argc, char **argv)
     signal(SIGPIPE, SIG_IGN);
 #endif
 
+    module_call_init(MODULE_INIT_TRACE);
     progname = basename(argv[0]);
     qemu_init_exec_dir(argv[0]);
 
diff --git a/qemu-nbd.c b/qemu-nbd.c
index 99297a5..361880b 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -533,6 +533,7 @@ int main(int argc, char **argv)
     sa_sigterm.sa_handler = termsig_handler;
     sigaction(SIGTERM, &sa_sigterm, NULL);
 
+    module_call_init(MODULE_INIT_TRACE);
     qcrypto_init(&error_fatal);
 
     module_call_init(MODULE_INIT_QOM);
diff --git a/scripts/tracetool/format/events_c.py b/scripts/tracetool/format/events_c.py
index 40ae395..8817555 100644
--- a/scripts/tracetool/format/events_c.py
+++ b/scripts/tracetool/format/events_c.py
@@ -60,3 +60,9 @@ def generate(events, backend):
     out('  NULL,',
         '};',
         '')
+
+    out('static void trace_register_events(void)',
+        '{',
+        '    trace_event_register_group(trace_events);',
+        '}',
+        'trace_init(trace_register_events)')
diff --git a/trace/control-internal.h b/trace/control-internal.h
index 9abbc96..a9d395a 100644
--- a/trace/control-internal.h
+++ b/trace/control-internal.h
@@ -15,7 +15,6 @@
 #include "qom/cpu.h"
 
 
-extern TraceEvent *trace_events[];
 extern int trace_events_enabled_count;
 
 
@@ -83,4 +82,7 @@ static inline bool trace_event_get_vcpu_state_dynamic(CPUState *vcpu,
     return trace_event_get_vcpu_state_dynamic_by_vcpu_id(vcpu, vcpu_id);
 }
 
+
+void trace_event_register_group(TraceEvent **events);
+
 #endif /* TRACE__CONTROL_INTERNAL_H */
diff --git a/trace/control.c b/trace/control.c
index 6b32511..a231327 100644
--- a/trace/control.c
+++ b/trace/control.c
@@ -29,6 +29,13 @@
 
 int trace_events_enabled_count;
 
+typedef struct TraceEventGroup {
+    TraceEvent **events;
+} TraceEventGroup;
+
+static TraceEventGroup *event_groups;
+static size_t nevent_groups;
+
 QemuOptsList qemu_trace_opts = {
     .name = "trace",
     .implied_opt_name = "enable",
@@ -50,6 +57,14 @@ QemuOptsList qemu_trace_opts = {
 };
 
 
+void trace_event_register_group(TraceEvent **events)
+{
+    event_groups = g_renew(TraceEventGroup, event_groups, nevent_groups + 1);
+    event_groups[nevent_groups].events = events;
+    nevent_groups++;
+}
+
+
 TraceEvent *trace_event_name(const char *name)
 {
     assert(name != NULL);
@@ -100,14 +115,20 @@ static bool pattern_glob(const char *pat, const char *ev)
 void trace_event_iter_init(TraceEventIter *iter, const char *pattern)
 {
     iter->event = 0;
+    iter->group = 0;
     iter->pattern = pattern;
 }
 
 TraceEvent *trace_event_iter_next(TraceEventIter *iter)
 {
-    while (trace_events[iter->event] != NULL) {
-        TraceEvent *ev = trace_events[iter->event];
+    while (iter->group < nevent_groups &&
+           event_groups[iter->group].events[iter->event] != NULL) {
+        TraceEvent *ev = event_groups[iter->group].events[iter->event];
         iter->event++;
+        if (event_groups[iter->group].events[iter->event] == NULL) {
+            iter->event = 0;
+            iter->group++;
+        }
         if (!iter->pattern ||
             pattern_glob(iter->pattern,
                          trace_event_get_name(ev))) {
diff --git a/trace/control.h b/trace/control.h
index cccd2a2..3f30a0c 100644
--- a/trace/control.h
+++ b/trace/control.h
@@ -15,6 +15,7 @@
 
 typedef struct TraceEventIter {
     size_t event;
+    size_t group;
     const char *pattern;
 } TraceEventIter;
 
diff --git a/vl.c b/vl.c
index f3abd99..610539a 100644
--- a/vl.c
+++ b/vl.c
@@ -3020,6 +3020,8 @@ int main(int argc, char **argv, char **envp)
     Error *err = NULL;
     bool list_data_dirs = false;
 
+    module_call_init(MODULE_INIT_TRACE);
+
     qemu_init_cpu_list();
     qemu_init_cpu_loop();
     qemu_mutex_lock_iothread();
-- 
2.7.4