1 files changed, 19 insertions, 38 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index ff7027199a9a..afb04b9b818a 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1689,22 +1689,14 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
                         if (!cpu_buffer->nr_pages_to_update)
                                 continue;
 
-                        /* The update must run on the CPU that is being updated. */
-                        preempt_disable();
-                        if (cpu == smp_processor_id() || !cpu_online(cpu)) {
+                        /* Can't run something on an offline CPU. */
+                        if (!cpu_online(cpu)) {
                                 rb_update_pages(cpu_buffer);
                                 cpu_buffer->nr_pages_to_update = 0;
                         } else {
-                                /*
-                                 * Can not disable preemption for schedule_work_on()
-                                 * on PREEMPT_RT.
-                                 */
-                                preempt_enable();
                                 schedule_work_on(cpu,
                                                 &cpu_buffer->update_pages_work);
-                                preempt_disable();
                         }
-                        preempt_enable();
                 }
 
                 /* wait for all the updates to complete */
@@ -1742,22 +1734,14 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
 
                 get_online_cpus();
 
-                preempt_disable();
-                /* The update must run on the CPU that is being updated. */
-                if (cpu_id == smp_processor_id() || !cpu_online(cpu_id))
+                /* Can't run something on an offline CPU. */
+                if (!cpu_online(cpu_id))
                         rb_update_pages(cpu_buffer);
                 else {
-                        /*
-                         * Can not disable preemption for schedule_work_on()
-                         * on PREEMPT_RT.
-                         */
-                        preempt_enable();
                         schedule_work_on(cpu_id,
                                          &cpu_buffer->update_pages_work);
                         wait_for_completion(&cpu_buffer->update_done);
-                        preempt_disable();
                 }
-                preempt_enable();
 
                 cpu_buffer->nr_pages_to_update = 0;
                 put_online_cpus();
@@ -1984,7 +1968,7 @@ rb_add_time_stamp(struct ring_buffer_event *event, u64 delta)
 
 /**
  * rb_update_event - update event type and data
- * @event: the even to update
+ * @event: the event to update
  * @type: the type of event
  * @length: the size of the event field in the ring buffer
  *
@@ -3357,21 +3341,16 @@ static void rb_iter_reset(struct ring_buffer_iter *iter)
         struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
 
         /* Iterator usage is expected to have record disabled */
-        if (list_empty(&cpu_buffer->reader_page->list)) {
-                iter->head_page = rb_set_head_page(cpu_buffer);
-                if (unlikely(!iter->head_page))
-                        return;
-                iter->head = iter->head_page->read;
-        } else {
-                iter->head_page = cpu_buffer->reader_page;
-                iter->head = cpu_buffer->reader_page->read;
-        }
+        iter->head_page = cpu_buffer->reader_page;
+        iter->head = cpu_buffer->reader_page->read;
+
+        iter->cache_reader_page = iter->head_page;
+        iter->cache_read = iter->head;
+
         if (iter->head)
                 iter->read_stamp = cpu_buffer->read_stamp;
         else
                 iter->read_stamp = iter->head_page->page->time_stamp;
-        iter->cache_reader_page = cpu_buffer->reader_page;
-        iter->cache_read = cpu_buffer->read;
 }
 
 /**
@@ -3764,18 +3743,20 @@ rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
                 return NULL;
 
         /*
-         * We repeat when a time extend is encountered.
-         * Since the time extend is always attached to a data event,
-         * we should never loop more than once.
-         * (We never hit the following condition more than twice).
+         * We repeat when a time extend is encountered or we hit
+         * the end of the page. Since the time extend is always attached
+         * to a data event, we should never loop more than three times.
+         * Once for going to next page, once on time extend, and
+         * finally once to get the event.
+         * (We never hit the following condition more than thrice).
          */
-        if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
+        if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3))
                 return NULL;
 
         if (rb_per_cpu_empty(cpu_buffer))
                 return NULL;
 
-        if (iter->head >= local_read(&iter->head_page->page->commit)) {
+        if (iter->head >= rb_page_size(iter->head_page)) {
                 rb_inc_iter(iter);
                 goto again;
         }