1 files changed, 42 insertions, 23 deletions

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 9eb7fed0bbaa..760e86df8c20 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -17,6 +17,7 @@
 #include <linux/slab.h>
 #include <linux/freezer.h>
 #include <linux/ptrace.h>
+#include <linux/uaccess.h>
 #include <trace/events/sched.h>
 
 static DEFINE_SPINLOCK(kthread_create_lock);
@@ -52,8 +53,21 @@ enum KTHREAD_BITS {
         KTHREAD_IS_PARKED,
 };
 
-#define to_kthread(tsk) \
-        container_of((tsk)->vfork_done, struct kthread, exited)
+#define __to_kthread(vfork)     \
+        container_of(vfork, struct kthread, exited)
+
+static inline struct kthread *to_kthread(struct task_struct *k)
+{
+        return __to_kthread(k->vfork_done);
+}
+
+static struct kthread *to_live_kthread(struct task_struct *k)
+{
+        struct completion *vfork = ACCESS_ONCE(k->vfork_done);
+        if (likely(vfork))
+                return __to_kthread(vfork);
+        return NULL;
+}
 
 /**
  * kthread_should_stop - should this kthread return now?
@@ -122,6 +136,24 @@ void *kthread_data(struct task_struct *task)
         return to_kthread(task)->data;
 }
 
+/**
+ * probe_kthread_data - speculative version of kthread_data()
+ * @task: possible kthread task in question
+ *
+ * @task could be a kthread task.  Return the data value specified when it
+ * was created if accessible.  If @task isn't a kthread task or its data is
+ * inaccessible for any reason, %NULL is returned.  This function requires
+ * that @task itself is safe to dereference.
+ */
+void *probe_kthread_data(struct task_struct *task)
+{
+        struct kthread *kthread = to_kthread(task);
+        void *data = NULL;
+
+        probe_kernel_read(&data, &kthread->data, sizeof(data));
+        return data;
+}
+
 static void __kthread_parkme(struct kthread *self)
 {
         __set_current_state(TASK_PARKED);
@@ -265,7 +297,7 @@ static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
         }
         /* It's safe because the task is inactive. */
         do_set_cpus_allowed(p, cpumask_of(cpu));
-        p->flags |= PF_THREAD_BOUND;
+        p->flags |= PF_NO_SETAFFINITY;
 }
 
 /**
@@ -311,19 +343,6 @@ struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
         return p;
 }
 
-static struct kthread *task_get_live_kthread(struct task_struct *k)
-{
-        struct kthread *kthread;
-
-        get_task_struct(k);
-        kthread = to_kthread(k);
-        /* It might have exited */
-        barrier();
-        if (k->vfork_done != NULL)
-                return kthread;
-        return NULL;
-}
-
 static void __kthread_unpark(struct task_struct *k, struct kthread *kthread)
 {
         clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
@@ -350,11 +369,10 @@ static void __kthread_unpark(struct task_struct *k, struct kthread *kthread)
  */
 void kthread_unpark(struct task_struct *k)
 {
-        struct kthread *kthread = task_get_live_kthread(k);
+        struct kthread *kthread = to_live_kthread(k);
 
         if (kthread)
                 __kthread_unpark(k, kthread);
-        put_task_struct(k);
 }
 
 /**
@@ -371,7 +389,7 @@ void kthread_unpark(struct task_struct *k)
  */
 int kthread_park(struct task_struct *k)
 {
-        struct kthread *kthread = task_get_live_kthread(k);
+        struct kthread *kthread = to_live_kthread(k);
         int ret = -ENOSYS;
 
         if (kthread) {
@@ -384,7 +402,6 @@ int kthread_park(struct task_struct *k)
                 }
                 ret = 0;
         }
-        put_task_struct(k);
         return ret;
 }
 
@@ -405,10 +422,13 @@ int kthread_park(struct task_struct *k)
  */
 int kthread_stop(struct task_struct *k)
 {
-        struct kthread *kthread = task_get_live_kthread(k);
+        struct kthread *kthread;
         int ret;
 
         trace_sched_kthread_stop(k);
+
+        get_task_struct(k);
+        kthread = to_live_kthread(k);
         if (kthread) {
                 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
                 __kthread_unpark(k, kthread);
@@ -416,10 +436,9 @@ int kthread_stop(struct task_struct *k)
                 wait_for_completion(&kthread->exited);
         }
         ret = k->exit_code;
-
         put_task_struct(k);
-        trace_sched_kthread_stop_ret(ret);
 
+        trace_sched_kthread_stop_ret(ret);
         return ret;
 }
 EXPORT_SYMBOL(kthread_stop);