sched: Fix kthread_bind() by moving the body of kthread_bind() to sched.c

Eric Paris reported that commit
f685ceacab07d3f6c236f04803e2f2f0dbcc5afb causes boot time
PREEMPT_DEBUG complaints.

 [    4.590699] BUG: using smp_processor_id() in preemptible [00000000] code: rmmod/1314
 [    4.593043] caller is task_hot+0x86/0xd0

Since kthread_bind() messes with scheduler internals, move the
body to sched.c, and lock the runqueue.

Reported-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Tested-by: Eric Paris <eparis@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1256813310.7574.3.camel@marge.simson.net>
[ v2: fix !SMP build and clean up ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 5fe709982caa1cacf9286b89954c2c625f2ca557..ab7ae57773e1b41f263407eb4a3bad1c95b41289 100644 (file)
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -149,29 +149,6 @@ struct task_struct *kthread_create(int (*threadfn)(void *data),
 }
 EXPORT_SYMBOL(kthread_create);
 
-/**
- * kthread_bind - bind a just-created kthread to a cpu.
- * @k: thread created by kthread_create().
- * @cpu: cpu (might not be online, must be possible) for @k to run on.
- *
- * Description: This function is equivalent to set_cpus_allowed(),
- * except that @cpu doesn't need to be online, and the thread must be
- * stopped (i.e., just returned from kthread_create()).
- */
-void kthread_bind(struct task_struct *k, unsigned int cpu)
-{
-       /* Must have done schedule() in kthread() before we set_task_cpu */
-       if (!wait_task_inactive(k, TASK_UNINTERRUPTIBLE)) {
-               WARN_ON(1);
-               return;
-       }
-       set_task_cpu(k, cpu);
-       k->cpus_allowed = cpumask_of_cpu(cpu);
-       k->rt.nr_cpus_allowed = 1;
-       k->flags |= PF_THREAD_BOUND;
-}
-EXPORT_SYMBOL(kthread_bind);
-
 /**
  * kthread_stop - stop a thread created by kthread_create().
  * @k: thread created by kthread_create().

diff --git a/kernel/sched.c b/kernel/sched.c
index bf21adb6c9fc4053eb76ccbc4359f6459d5c81c5..5cb7d637e33a6aeceb4d3a682381bd3de3ae53d5 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1996,6 +1996,38 @@ static inline void check_class_changed(struct rq *rq, struct task_struct *p,
                p->sched_class->prio_changed(rq, p, oldprio, running);
 }
 
+/**
+ * kthread_bind - bind a just-created kthread to a cpu.
+ * @k: thread created by kthread_create().
+ * @cpu: cpu (might not be online, must be possible) for @k to run on.
+ *
+ * Description: This function is equivalent to set_cpus_allowed(),
+ * except that @cpu doesn't need to be online, and the thread must be
+ * stopped (i.e., just returned from kthread_create()).
+ *
+ * Function lives here instead of kthread.c because it messes with
+ * scheduler internals which require locking.
+ */
+void kthread_bind(struct task_struct *p, unsigned int cpu)
+{
+       struct rq *rq = cpu_rq(cpu);
+       unsigned long flags;
+
+       /* Must have done schedule() in kthread() before we set_task_cpu */
+       if (!wait_task_inactive(p, TASK_UNINTERRUPTIBLE)) {
+               WARN_ON(1);
+               return;
+       }
+
+       spin_lock_irqsave(&rq->lock, flags);
+       set_task_cpu(p, cpu);
+       p->cpus_allowed = cpumask_of_cpu(cpu);
+       p->rt.nr_cpus_allowed = 1;
+       p->flags |= PF_THREAD_BOUND;
+       spin_unlock_irqrestore(&rq->lock, flags);
+}
+EXPORT_SYMBOL(kthread_bind);
+
 #ifdef CONFIG_SMP
 /*
  * Is this task likely cache-hot: