[PATCH 3/3] Toggle tracepoint state

Prerna Saxena
2010-06-16T12:44:41Z

This patch adds support for dynamically enabling/disabling of tracepoints.
This is done by internally maintaining each tracepoint's state, and
permitting logging of data from a tracepoint only if it is in an
'active' state.

Monitor commands added :
1) info tracepoints : to view all available tracepoints and
their state.
2) tracepoint NAME on|off : to enable/disable data logging from a
given tracepoint.
Eg, tracepoint paio_submit off
disables logging of data when
paio_submit is hit.

Signed-off-by: Prerna Saxena <prerna@linux.vnet.ibm.com>
---

monitor.c | 16 ++++++++++++++
qemu-monitor.hx | 18 ++++++++++++++++
simpletrace.c | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
tracetool | 30 +++++++++++++++++++++++---
vl.c | 6 +++++
5 files changed, 129 insertions(+), 4 deletions(-)

diff --git a/monitor.c b/monitor.c
index 8b60830..238bdf0 100644
--- a/monitor.c
+++ b/monitor.c
@@ -548,6 +548,15 @@ static void do_commit(Monitor *mon, const QDict *qdict)
}
}

+#ifdef CONFIG_SIMPLE_TRACE
+static void do_change_tracepoint_state(Monitor *mon, const QDict *qdict)
+{
+ const char *tp_name = qdict_get_str(qdict, "name");
+ bool new_state = qdict_get_bool(qdict, "option");
+ change_tracepoint_state(tp_name, new_state);
+}
+#endif
+
static void user_monitor_complete(void *opaque, QObject *ret_data)
{
MonitorCompletionData *data = (MonitorCompletionData *)opaque;
@@ -2791,6 +2800,13 @@ static const mon_cmd_t info_cmds[] = {
.help = "show current contents of trace buffer",
.mhandler.info = do_info_trace,
},
+ {
+ .name = "tracepoints",
+ .args_type = "",
+ .params = "",
+ .help = "show available tracepoints & their state",
+ .mhandler.info = do_info_all_tracepoints,
+ },
#endif
{
.name = NULL,
diff --git a/qemu-monitor.hx b/qemu-monitor.hx
index 766c30f..8540b8f 100644
--- a/qemu-monitor.hx
+++ b/qemu-monitor.hx
@@ -117,6 +117,8 @@ show device tree
#ifdef CONFIG_SIMPLE_TRACE
@item info trace
show contents of trace buffer
+@item info tracepoints
+show available tracepoints and their state
#endif
@end table
ETEXI
@@ -225,6 +227,22 @@ STEXI
@item logfile @var{filename}
@findex logfile
Output logs to @var{filename}.
+#ifdef CONFIG_SIMPLE_TRACE
+ETEXI
+
+ {
+ .name = "tracepoint",
+ .args_type = "name:s,option:b",
+ .params = "name on|off",
+ .help = "changes status of a specific tracepoint",
+ .mhandler.cmd = do_change_tracepoint_state,
+ },
+
+STEXI
+@item tracepoint
+@findex tracepoint
+changes status of a tracepoint
+#endif
ETEXI

{
diff --git a/simpletrace.c b/simpletrace.c
index 239ae3f..4221a8f 100644
--- a/simpletrace.c
+++ b/simpletrace.c
@@ -3,6 +3,12 @@
#include "trace.h"

typedef struct {
+ char *tp_name;
+ bool state;
+ unsigned int hash;
+} Tracepoint;
+
+typedef struct {
unsigned long event;
unsigned long x1;
unsigned long x2;
@@ -18,11 +24,29 @@ enum {
static TraceRecord trace_buf[TRACE_BUF_LEN];
static unsigned int trace_idx;
static FILE *trace_fp;
+static Tracepoint trace_list[NR_TRACEPOINTS];
+
+void init_tracepoint(const char *tname, TraceEvent tevent)
+{
+ if (!tname || tevent > NR_TRACEPOINTS) {
+ return;
+ }
+
+ trace_list[tevent].tp_name = (char*)qemu_malloc(strlen(tname)+1);
+ strncpy(trace_list[tevent].tp_name, tname, strlen(tname));
+ trace_list[tevent].hash = qemu_hash(tname);
+ trace_list[tevent].state = 1; /* Enable all by default */
+}

static void trace(TraceEvent event, unsigned long x1,
unsigned long x2, unsigned long x3,
unsigned long x4, unsigned long x5) {
TraceRecord *rec = &trace_buf[trace_idx];
+
+ if (!trace_list[event].state) {
+ return;
+ }
+
rec->event = event;
rec->x1 = x1;
rec->x2 = x2;
@@ -75,3 +99,42 @@ void do_info_trace(Monitor *mon)
trace_buf[i].x3, trace_buf[i].x4, trace_buf[i].x5);
}
}
+
+void do_info_all_tracepoints(Monitor *mon)
+{
+ unsigned int i;
+
+ for (i=0; i<NR_TRACEPOINTS; i++) {
+ monitor_printf(mon, "%s [Event ID %u] : state %u\n",
+ trace_list[i].tp_name, i, trace_list[i].state);
+ }
+}
+
+static Tracepoint* find_tracepoint_by_name(const char *tname)
+{
+ unsigned int i, name_hash;
+
+ if (!tname) {
+ return NULL;
+ }
+
+ name_hash = qemu_hash(tname);
+
+ for (i=0; i<NR_TRACEPOINTS; i++) {
+ if (trace_list[i].hash == name_hash &&
+ !strncmp(trace_list[i].tp_name, tname, strlen(tname))) {
+ return &trace_list[i];
+ }
+ }
+ return NULL; /* indicates end of list reached without a match */
+}
+
+void change_tracepoint_state(const char *tname, bool tstate)
+{
+ Tracepoint *tp;
+
+ tp = find_tracepoint_by_name(tname);
+ if (tp) {
+ tp->state = tstate;
+ }
+}
diff --git a/tracetool b/tracetool
index 2c73bab..00af205 100755
--- a/tracetool
+++ b/tracetool
@@ -123,14 +123,20 @@ linetoc_end_nop()
linetoh_begin_simple()
{
cat <<EOF
+#include <stdbool.h>
+
typedef unsigned int TraceEvent;

+void init_tracepoint_table(void);
+void init_tracepoint(const char *tname, TraceEvent tevent);
void trace1(TraceEvent event, unsigned long x1);
void trace2(TraceEvent event, unsigned long x1, unsigned long x2);
void trace3(TraceEvent event, unsigned long x1, unsigned long x2, unsigned long x3);
void trace4(TraceEvent event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4);
void trace5(TraceEvent event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4, unsigned long x5);
void do_info_trace(Monitor *mon);
+void do_info_all_tracepoints(Monitor *mon);
+void change_tracepoint_state(const char *tname, bool tstate);
EOF

simple_event_num=0
@@ -163,22 +169,38 @@ EOF

linetoh_end_simple()
{
- return
+ cat <<EOF
+#define NR_TRACEPOINTS $simple_event_num
+EOF
}

linetoc_begin_simple()
{
- return
+ cat <<EOF
+#include "trace.h"
+
+void init_tracepoint_table(void) {
+EOF
+ simple_event_num=0
+
}

linetoc_simple()
{
- return
+ local name
+ name=$(get_name "$1")
+ cat <<EOF
+init_tracepoint("$name", $simple_event_num);
+EOF
+ simple_event_num=$((simple_event_num + 1))
}

linetoc_end_simple()
{
- return
+ cat <<EOF
+return;
+}
+EOF
}

linetoh_begin_ust()
diff --git a/vl.c b/vl.c
index 328395e..dd07904 100644
--- a/vl.c
+++ b/vl.c
@@ -163,6 +163,9 @@ int main(int argc, char **argv)
#include "cpus.h"
#include "arch_init.h"

+#ifdef CONFIG_SIMPLE_TRACE
+#include "trace.h"
+#endif
//#define DEBUG_NET
//#define DEBUG_SLIRP

@@ -3604,6 +3607,9 @@ int main(int argc, char **argv, char **envp)
if (net_init_clients() < 0) {
exit(1);
}
+#ifdef CONFIG_SIMPLE_TRACE
+ init_tracepoint_table();
+#endif

/* init the bluetooth world */
if (foreach_device_config(DEV_BT, bt_parse))