Merge branch 'sched/new-API-sched_setscheduler' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'sched/new-API-sched_setscheduler' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  sched: add new API sched_setscheduler_nocheck: add a flag to control access checks

3 files changed, 38 insertions, 14 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index c74b0d23c752..2317a2178104 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4995,16 +4995,8 @@ __setscheduler(struct rq *rq, struct task_struct *p, int policy, int prio)
         set_load_weight(p);
 }
 
-/**
- * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
- * @p: the task in question.
- * @policy: new policy.
- * @param: structure containing the new RT priority.
- *
- * NOTE that the task may be already dead.
- */
-int sched_setscheduler(struct task_struct *p, int policy,
-                       struct sched_param *param)
+static int __sched_setscheduler(struct task_struct *p, int policy,
+                                struct sched_param *param, bool user)
 {
         int retval, oldprio, oldpolicy = -1, on_rq, running;
         unsigned long flags;
@@ -5036,7 +5028,7 @@ recheck:
         /*
          * Allow unprivileged RT tasks to decrease priority:
          */
-        if (!capable(CAP_SYS_NICE)) {
+        if (user && !capable(CAP_SYS_NICE)) {
                 if (rt_policy(policy)) {
                         unsigned long rlim_rtprio;
 
@@ -5072,7 +5064,8 @@ recheck:
          * Do not allow realtime tasks into groups that have no runtime
          * assigned.
          */
-        if (rt_policy(policy) && task_group(p)->rt_bandwidth.rt_runtime == 0)
+        if (user
+            && rt_policy(policy) && task_group(p)->rt_bandwidth.rt_runtime == 0)
                 return -EPERM;
 #endif
 
@@ -5121,8 +5114,39 @@ recheck:
 
         return 0;
 }
+
+/**
+ * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
+ * @p: the task in question.
+ * @policy: new policy.
+ * @param: structure containing the new RT priority.
+ *
+ * NOTE that the task may be already dead.
+ */
+int sched_setscheduler(struct task_struct *p, int policy,
+                       struct sched_param *param)
+{
+        return __sched_setscheduler(p, policy, param, true);
+}
 EXPORT_SYMBOL_GPL(sched_setscheduler);
 
+/**
+ * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
+ * @p: the task in question.
+ * @policy: new policy.
+ * @param: structure containing the new RT priority.
+ *
+ * Just like sched_setscheduler, only don't bother checking if the
+ * current context has permission.  For example, this is needed in
+ * stop_machine(): we create temporary high priority worker threads,
+ * but our caller might not have that capability.
+ */
+int sched_setscheduler_nocheck(struct task_struct *p, int policy,
+                               struct sched_param *param)
+{
+        return __sched_setscheduler(p, policy, param, false);
+}
+
 static int
 do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
 {
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 36e061740047..afd9120c2fc4 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -645,7 +645,7 @@ static int __cpuinit cpu_callback(struct notifier_block *nfb,
 
                 p = per_cpu(ksoftirqd, hotcpu);
                 per_cpu(ksoftirqd, hotcpu) = NULL;
-                sched_setscheduler(p, SCHED_FIFO, &param);
+                sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
                 kthread_stop(p);
                 takeover_tasklets(hotcpu);
                 break;
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index b7350bbfb076..ba9b2054ecbd 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -187,7 +187,7 @@ struct task_struct *__stop_machine_run(int (*fn)(void *), void *data,
                 struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
 
                 /* One high-prio thread per cpu.  We'll do this one. */
-                sched_setscheduler(p, SCHED_FIFO, &param);
+                sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
                 kthread_bind(p, cpu);
                 wake_up_process(p);
                 wait_for_completion(&smdata.done);