diff options
| -rw-r--r-- | kernel/sched.c | 33 |
1 files changed, 17 insertions, 16 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index 8e5e2af64509..862df56ed454 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -3038,7 +3038,7 @@ static int setscheduler(pid_t pid, int policy, struct sched_param __user *param) { struct sched_param lp; int retval = -EINVAL; - int oldprio; + int oldprio, oldpolicy = -1; prio_array_t *array; unsigned long flags; runqueue_t *rq; @@ -3060,23 +3060,17 @@ static int setscheduler(pid_t pid, int policy, struct sched_param __user *param) retval = -ESRCH; if (!p) - goto out_unlock_tasklist; - - /* - * To be able to change p->policy safely, the apropriate - * runqueue lock must be held. - */ - rq = task_rq_lock(p, &flags); - + goto out_unlock; +recheck: + /* double check policy once rq lock held */ if (policy < 0) - policy = p->policy; + policy = oldpolicy = p->policy; else { retval = -EINVAL; if (policy != SCHED_FIFO && policy != SCHED_RR && policy != SCHED_NORMAL) goto out_unlock; } - /* * Valid priorities for SCHED_FIFO and SCHED_RR are * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL is 0. @@ -3098,7 +3092,17 @@ static int setscheduler(pid_t pid, int policy, struct sched_param __user *param) retval = security_task_setscheduler(p, policy, &lp); if (retval) goto out_unlock; - + /* + * To be able to change p->policy safely, the apropriate + * runqueue lock must be held. + */ + rq = task_rq_lock(p, &flags); + /* recheck policy now with rq lock held */ + if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) { + policy = oldpolicy = -1; + task_rq_unlock(rq, &flags); + goto recheck; + } array = p->array; if (array) deactivate_task(p, task_rq(p)); @@ -3118,12 +3122,9 @@ static int setscheduler(pid_t pid, int policy, struct sched_param __user *param) } else if (TASK_PREEMPTS_CURR(p, rq)) resched_task(rq->curr); } - -out_unlock: task_rq_unlock(rq, &flags); -out_unlock_tasklist: +out_unlock: read_unlock_irq(&tasklist_lock); - out_nounlock: return retval; } |