ftrace: do_each_pid_task() needs rcu lock

"ftrace: use struct pid" commit 978f3a4 converted ftrace_pid_trace to "struct pid*". But we can't use do_each_pid_task() without rcu_read_lock() even if we know the pid itself can't go away (it was pinned in ftrace_pid_write). The exiting task can detach itself from this pid at any moment. Signed-off-by: Oleg Nesterov <[email protected]> Signed-off-by: Ingo Molnar <[email protected]>
mrcsosa · Feb 3, 2009 · 229c4ef · 229c4ef
1 parent b1792e3
commit 229c4ef
Showing 1 changed file with 5 additions and 0 deletions.
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
@@ -1737,19 +1737,24 @@ static void clear_ftrace_pid(struct pid *pid)
 {
 	struct task_struct *p;
 
+	rcu_read_lock();
 	do_each_pid_task(pid, PIDTYPE_PID, p) {
 		clear_tsk_trace_trace(p);
 	} while_each_pid_task(pid, PIDTYPE_PID, p);
+	rcu_read_unlock();
+
 	put_pid(pid);
 }
 
 static void set_ftrace_pid(struct pid *pid)
 {
 	struct task_struct *p;
 
+	rcu_read_lock();
 	do_each_pid_task(pid, PIDTYPE_PID, p) {
 		set_tsk_trace_trace(p);
 	} while_each_pid_task(pid, PIDTYPE_PID, p);
+	rcu_read_unlock();
 }
 
 static void clear_ftrace_pid_task(struct pid **pid)