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Commit 1a551ae7 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Ingo Molnar
Browse files

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: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <20091209100706.862897167@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 23f5d142

kernel/sched.c

+3 −3
Original line number Diff line number Diff line
@@ -6873,7 +6873,7 @@ SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid, 
		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 @@ SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid, 
	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;

}