Merge branch 'master' into percpu

[safe/jmp/linux-2.6] / kernel / trace / ring_buffer.c

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index eb6c898..0287f9f 100644 (file)
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -465,6 +465,8 @@ struct ring_buffer_iter {
        struct ring_buffer_per_cpu      *cpu_buffer;
        unsigned long                   head;
        struct buffer_page              *head_page;
+       struct buffer_page              *cache_reader_page;
+       unsigned long                   cache_read;
        u64                             read_stamp;
 };
 
@@ -2717,6 +2719,8 @@ static void rb_iter_reset(struct ring_buffer_iter *iter)
                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;
 }
 
 /**
@@ -2870,7 +2874,7 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
         * Splice the empty reader page into the list around the head.
         */
        reader = rb_set_head_page(cpu_buffer);
-       cpu_buffer->reader_page->list.next = reader->list.next;
+       cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
        cpu_buffer->reader_page->list.prev = reader->list.prev;
 
        /*
@@ -2907,7 +2911,7 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
         *
         * Now make the new head point back to the reader page.
         */
-       reader->list.next->prev = &cpu_buffer->reader_page->list;
+       rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
        rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
 
        /* Finally update the reader page to the new head */
@@ -3061,13 +3065,22 @@ rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
        struct ring_buffer_event *event;
        int nr_loops = 0;
 
-       if (ring_buffer_iter_empty(iter))
-               return NULL;
-
        cpu_buffer = iter->cpu_buffer;
        buffer = cpu_buffer->buffer;
 
+       /*
+        * Check if someone performed a consuming read to
+        * the buffer. A consuming read invalidates the iterator
+        * and we need to reset the iterator in this case.
+        */
+       if (unlikely(iter->cache_read != cpu_buffer->read ||
+                    iter->cache_reader_page != cpu_buffer->reader_page))
+               rb_iter_reset(iter);
+
  again:
+       if (ring_buffer_iter_empty(iter))
+               return NULL;
+
        /*
         * We repeat when a timestamp is encountered.
         * We can get multiple timestamps by nested interrupts or also
@@ -3082,6 +3095,11 @@ rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
        if (rb_per_cpu_empty(cpu_buffer))
                return NULL;
 
+       if (iter->head >= local_read(&iter->head_page->page->commit)) {
+               rb_inc_iter(iter);
+               goto again;
+       }
+
        event = rb_iter_head_event(iter);
 
        switch (event->type_len) {