2.6.26.6-rt10 added /debug/tracing/function_trace_stop which is a very
quick way of starting and stopping the tracer. It does not disable the
mcount call, but just sets a variable in the mcount call to return.
This patch tries to open the function_trace_stop file and if it succeeds
it will use the trace stop to start and stop the tracer an keep the ftrace
enabled the entire time.
Signed-off-by: Steven Rostedt <srostedt@xxxxxxxxxx>
---
src/cyclictest/cyclictest.c | 37 +++++++++++++++++++++++++++++++++----
1 file changed, 33 insertions(+), 4 deletions(-)
Index: rt-tests.git/src/cyclictest/cyclictest.c
===================================================================
--- rt-tests.git.orig/src/cyclictest/cyclictest.c 2008-10-13 15:04:11.000000000 -0400
+++ rt-tests.git/src/cyclictest/cyclictest.c 2008-10-13 15:13:36.000000000 -0400
@@ -134,6 +134,7 @@ static int tracetype;
static int lockall = 0;
static int traceenable_fd = -1;
+static int funcstop_fd = -1;
/* Backup of kernel variables that we modify */
static struct kvars {
@@ -153,7 +154,8 @@ enum kernelversion {
KV_NOT_26,
KV_26_LT18,
KV_26_LT24,
- KV_26_CURR
+ KV_26_CURR,
+ KV_26_QUICKSTOP,
};
enum {
@@ -223,7 +225,7 @@ static void setkernvar(const char *name,
int i;
char oldvalue[KVALUELEN];
- if (kernelversion != KV_26_CURR) {
+ if (kernelversion < KV_26_CURR) {
if (kernvar(O_RDONLY, name, oldvalue, sizeof(oldvalue)))
fprintf(stderr, "could not retrieve %s\n", name);
else {
@@ -283,6 +285,11 @@ void set_trace_enable(char val)
write(traceenable_fd, &val, 1);
}
+static void setfuncstop(char val)
+{
+ write(funcstop_fd, &val, 1);
+}
+
void tracing(int on)
{
if (on) {
@@ -290,6 +297,7 @@ void tracing(int on)
case KV_26_LT18: gettimeofday(0,(struct timezone *)1); break;
case KV_26_LT24: prctl(0, 1); break;
case KV_26_CURR: set_trace_enable('1'); break;
+ case KV_26_QUICKSTOP: setfuncstop('0'); break;
default: break;
}
} else {
@@ -297,6 +305,7 @@ void tracing(int on)
case KV_26_LT18: gettimeofday(0,0); break;
case KV_26_LT24: prctl(0, 0); break;
case KV_26_CURR: set_trace_enable('0'); break;
+ case KV_26_QUICKSTOP: setfuncstop('1'); break;
default: break;
}
}
@@ -378,7 +387,7 @@ void *timerthread(void *param)
interval.tv_nsec = (par->interval % USEC_PER_SEC) * 1000;
if (tracelimit) {
- if (kernelversion == KV_26_CURR) {
+ if (kernelversion >= KV_26_CURR) {
char buffer[32];
int ret;
@@ -858,6 +867,19 @@ int main(int argc, char **argv)
fprintf(stderr, "ERROR: %s not found\n"
"debug fs not mounted, "
"TRACERs not configured?\n", testname);
+ } else {
+ char *name = "function_trace_stop";
+
+ strncpy(testname, fileprefix, sizeof(testname));
+ strncat(testname, name, sizeof(testname) - strlen(fileprefix));
+ funcstop_fd = open(testname, O_RDWR);
+ if (funcstop_fd >= 0) {
+ /* enable tracing */
+ tracing(1);
+ kernelversion = KV_26_QUICKSTOP;
+ /* stop it */
+ tracing(0);
+ }
}
} else if (tracelimit)
fileprefix = procfileprefix;
@@ -963,9 +985,16 @@ int main(int argc, char **argv)
munlockall();
/* Be a nice program, cleanup */
- if (kernelversion != KV_26_CURR)
+ if (kernelversion < KV_26_CURR)
restorekernvars();
+ if (funcstop_fd >= 0) {
+ /* disable tracing */
+ kernelversion = KV_26_CURR;
+ tracing(0);
+ close(funcstop_fd);
+ }
+
if (traceenable_fd >= 0)
close(traceenable_fd);
--
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