sched: Use rcu in sched_get_rr_param()
read_lock(&tasklist_lock) does not protect
sys_sched_get_rr_param() against a concurrent update of the
policy or scheduler parameters as do_sched_scheduler() does not
take the tasklist_lock.
The access to task->sched_class->get_rr_interval is protected by
task_rq_lock(task).
Use rcu_read_lock() to protect find_task_by_vpid() and prevent
the task struct from going away.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <20091209100706.862897167@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sched.c b/kernel/sched.c
index 7989312..db5c266 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6873,7 +6873,7 @@
return -EINVAL;
retval = -ESRCH;
- read_lock(&tasklist_lock);
+ rcu_read_lock();
p = find_process_by_pid(pid);
if (!p)
goto out_unlock;
@@ -6886,13 +6886,13 @@
time_slice = p->sched_class->get_rr_interval(rq, p);
task_rq_unlock(rq, &flags);
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();
jiffies_to_timespec(time_slice, &t);
retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
return retval;
out_unlock:
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();
return retval;
}