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sched: Use rcu in sched_get_rr_param()

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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>
This commit is contained in:
Thomas Gleixner 2009-12-09 10:15:11 +00:00 committed by Ingo Molnar
parent 23f5d14251
commit 1a551ae715
1 changed files with 3 additions and 3 deletions
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6
kernel/sched.c
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@ -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;
}