1 files changed, 25 insertions, 3 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index b17a30350f06..c5049f54a275 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 */