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Subject[PATCH 2/3] ftrace: use task struct trace flag to filter on pid
From: Steven Rostedt <srostedt@redhat.com>

Impact: clean up

Use the new task struct trace flags to determine if a process should be
traced or not.

Note: this moves the searching of the pid to the slow path of setting
the pid field. This needs to be converted to the pid name space.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
kernel/trace/ftrace.c | 28 +++++++++++++++++++++++++---
1 files changed, 25 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index b17a303..c5049f5 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -47,7 +47,7 @@
int ftrace_enabled __read_mostly;
static int last_ftrace_enabled;

-/* ftrace_pid_trace >= 0 will only trace threads with this pid */
+/* set when tracing only a pid */
static int ftrace_pid_trace = -1;

/* Quick disabling of function tracer. */
@@ -90,7 +90,7 @@ static void ftrace_list_func(unsigned long ip, unsigned long parent_ip)

static void ftrace_pid_func(unsigned long ip, unsigned long parent_ip)
{
- if (current->pid != ftrace_pid_trace)
+ if (!test_tsk_trace_trace(current))
return;

ftrace_pid_function(ip, parent_ip);
@@ -1714,11 +1714,33 @@ ftrace_pid_write(struct file *filp, const char __user *ubuf,
ftrace_pid_trace = -1;

} else {
+ struct task_struct *p;
+ int found = 0;

if (ftrace_pid_trace == val)
goto out;

- ftrace_pid_trace = val;
+ /*
+ * 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;
+ }
}

/* update the function call */
--
1.5.6.5
--


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