1 files changed, 18 insertions, 2 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 533af75329e6..dba52b62cef8 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -895,7 +895,7 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
          * task has exited, don't wait
          */
         cic = cfqd->active_cic;
-        if (!cic || !cic->ioc->task)
+        if (!cic || !atomic_read(&cic->ioc->nr_tasks))
                 return;
 
         /*
@@ -1178,6 +1178,8 @@ static void cfq_free_io_context(struct io_context *ioc)
 
         ioc->ioc_data = NULL;
 
+        spin_lock(&ioc->lock);
+
         while ((n = rb_first(&ioc->cic_root)) != NULL) {
                 __cic = rb_entry(n, struct cfq_io_context, rb_node);
                 rb_erase(&__cic->rb_node, &ioc->cic_root);
@@ -1189,6 +1191,8 @@ static void cfq_free_io_context(struct io_context *ioc)
 
         if (ioc_gone && !elv_ioc_count_read(ioc_count))
                 complete(ioc_gone);
+
+        spin_unlock(&ioc->lock);
 }
 
 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
@@ -1243,6 +1247,7 @@ static void cfq_exit_io_context(struct io_context *ioc)
 
         ioc->ioc_data = NULL;
 
+        spin_lock(&ioc->lock);
         /*
          * put the reference this task is holding to the various queues
          */
@@ -1253,6 +1258,8 @@ static void cfq_exit_io_context(struct io_context *ioc)
                 cfq_exit_single_io_context(__cic);
                 n = rb_next(n);
         }
+
+        spin_unlock(&ioc->lock);
 }
 
 static struct cfq_io_context *
@@ -1349,6 +1356,8 @@ static void cfq_ioc_set_ioprio(struct io_context *ioc)
         struct cfq_io_context *cic;
         struct rb_node *n;
 
+        spin_lock(&ioc->lock);
+
         ioc->ioprio_changed = 0;
 
         n = rb_first(&ioc->cic_root);
@@ -1358,6 +1367,8 @@ static void cfq_ioc_set_ioprio(struct io_context *ioc)
                 changed_ioprio(cic);
                 n = rb_next(n);
         }
+
+        spin_unlock(&ioc->lock);
 }
 
 static struct cfq_queue *
@@ -1502,6 +1513,7 @@ cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc)
         if (cic && cic->key == cfqd)
                 return cic;
 
+        spin_lock(&ioc->lock);
 restart:
         n = ioc->cic_root.rb_node;
         while (n) {
@@ -1519,10 +1531,12 @@ restart:
                         n = n->rb_right;
                 else {
                         ioc->ioc_data = cic;
+                        spin_unlock(&ioc->lock);
                         return cic;
                 }
         }
 
+        spin_unlock(&ioc->lock);
         return NULL;
 }
 
@@ -1536,6 +1550,7 @@ cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
         unsigned long flags;
         void *k;
 
+        spin_lock(&ioc->lock);
         cic->ioc = ioc;
         cic->key = cfqd;
 
@@ -1566,6 +1581,7 @@ restart:
         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
         list_add(&cic->queue_list, &cfqd->cic_list);
         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
+        spin_unlock(&ioc->lock);
 }
 
 /*
@@ -1659,7 +1675,7 @@ cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 
         enable_idle = cfq_cfqq_idle_window(cfqq);
 
-        if (!cic->ioc->task || !cfqd->cfq_slice_idle ||
+        if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
             (cfqd->hw_tag && CIC_SEEKY(cic)))
                 enable_idle = 0;
         else if (sample_valid(cic->ttime_samples)) {