From 229c4ef8ae56d69f8dec64533bf1c7f8070c1a4a Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@redhat.com>
Date: Tue, 3 Feb 2009 20:39:04 +0100
Subject: [PATCH] ftrace: do_each_pid_task() needs rcu lock
"ftrace: use struct pid" commit 978f3a45d9499c7a447ca7615455cefb63d44165
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 <oleg@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/trace/ftrace.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 7dcf6e9f2b04..9a236ffe2aa4 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1737,9 +1737,12 @@ 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);
}
@@ -1747,9 +1750,11 @@ 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)