Commit 1a551ae7 authored Dec 09, 2009 by Thomas Gleixner Committed by Ingo Molnar Dec 14, 2009

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>

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;
		}

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