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Subject[PATCH 2/3] ftrace: use struct pid
From: Steven Rostedt <srostedt@redhat.com>

Impact: clean up

Eric Biederman suggested using the struct pid for filtering on
pids in the kernel. This patch is based off of a demonstration
of an implementation that Eric sent me in an email.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
kernel/trace/ftrace.c | 76 ++++++++++++++++++++++++++++--------------------
kernel/trace/trace.h | 4 +-
2 files changed, 46 insertions(+), 34 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 57592a9..10b1d7c 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -48,7 +48,7 @@ int ftrace_enabled __read_mostly;
static int last_ftrace_enabled;

/* set when tracing only a pid */
-int ftrace_pid_trace = -1;
+struct pid *ftrace_pid_trace;

/* Quick disabling of function tracer. */
int function_trace_stop;
@@ -153,7 +153,7 @@ static int __register_ftrace_function(struct ftrace_ops *ops)
else
func = ftrace_list_func;

- if (ftrace_pid_trace >= 0) {
+ if (ftrace_pid_trace) {
set_ftrace_pid_function(func);
func = ftrace_pid_func;
}
@@ -209,7 +209,7 @@ static int __unregister_ftrace_function(struct ftrace_ops *ops)
if (ftrace_list->next == &ftrace_list_end) {
ftrace_func_t func = ftrace_list->func;

- if (ftrace_pid_trace >= 0) {
+ if (ftrace_pid_trace) {
set_ftrace_pid_function(func);
func = ftrace_pid_func;
}
@@ -239,7 +239,7 @@ static void ftrace_update_pid_func(void)

func = ftrace_trace_function;

- if (ftrace_pid_trace >= 0) {
+ if (ftrace_pid_trace) {
set_ftrace_pid_function(func);
func = ftrace_pid_func;
} else {
@@ -1678,18 +1678,40 @@ ftrace_pid_read(struct file *file, char __user *ubuf,
char buf[64];
int r;

- if (ftrace_pid_trace >= 0)
- r = sprintf(buf, "%u\n", ftrace_pid_trace);
+ if (ftrace_pid_trace)
+ r = sprintf(buf, "%u\n", pid_nr(ftrace_pid_trace));
else
r = sprintf(buf, "no pid\n");

return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
}

+static void clear_ftrace_pid_task(struct pid **pid)
+{
+ struct task_struct *p;
+
+ do_each_pid_task(*pid, PIDTYPE_PID, p) {
+ clear_tsk_trace_trace(p);
+ } while_each_pid_task(*pid, PIDTYPE_PID, p);
+ put_pid(*pid);
+
+ *pid = NULL;
+}
+
+static void set_ftrace_pid_task(struct pid *pid)
+{
+ struct task_struct *p;
+
+ do_each_pid_task(pid, PIDTYPE_PID, p) {
+ set_tsk_trace_trace(p);
+ } while_each_pid_task(pid, PIDTYPE_PID, p);
+}
+
static ssize_t
ftrace_pid_write(struct file *filp, const char __user *ubuf,
size_t cnt, loff_t *ppos)
{
+ struct pid *pid;
char buf[64];
long val;
int ret;
@@ -1707,40 +1729,30 @@ ftrace_pid_write(struct file *filp, const char __user *ubuf,
return ret;

mutex_lock(&ftrace_start_lock);
- if (ret < 0) {
+ if (val < 0) {
/* disable pid tracing */
- if (ftrace_pid_trace < 0)
+ if (!ftrace_pid_trace)
goto out;
- ftrace_pid_trace = -1;
+
+ clear_ftrace_pid_task(&ftrace_pid_trace);

} else {
- struct task_struct *p;
- int found = 0;
+ pid = find_get_pid(val);

- if (ftrace_pid_trace == val)
+ if (pid == ftrace_pid_trace) {
+ put_pid(pid);
goto out;
-
- /*
- * Find the task that matches this pid.
- * TODO: use pid namespaces instead.
- */
- rcu_read_lock();
- for_each_process(p) {
- if (p->pid == val) {
- found = 1;
- set_tsk_trace_trace(p);
- } else if (test_tsk_trace_trace(p))
- clear_tsk_trace_trace(p);
}
- rcu_read_unlock();

- if (found)
- ftrace_pid_trace = val;
- else {
- if (ftrace_pid_trace < 0)
- goto out;
- ftrace_pid_trace = -1;
- }
+ if (ftrace_pid_trace)
+ clear_ftrace_pid_task(&ftrace_pid_trace);
+
+ if (!pid)
+ goto out;
+
+ ftrace_pid_trace = pid;
+
+ set_ftrace_pid_task(ftrace_pid_trace);
}

/* update the function call */
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 95fff37..8b81b4d 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -541,11 +541,11 @@ print_graph_function(struct trace_iterator *iter)
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

-extern int ftrace_pid_trace;
+extern struct pid *ftrace_pid_trace;

static inline int ftrace_trace_task(struct task_struct *task)
{
- if (ftrace_pid_trace < 0)
+ if (ftrace_pid_trace)
return 1;

return test_tsk_trace_trace(task);
--
1.5.6.5
--


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