---

yaml
---
r: 339059
b: refs/heads/master
c: 9366c1b
h: refs/heads/master
i:
  339057: aa63c9a
  339055: 99663b6
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 54f7be5b831254199522523ccab4c3d954bbf576
+refs/heads/master: 9366c1ba13fbc41bdb57702e75ca4382f209c82f

trunk/kernel/trace/ring_buffer.c

@@ -3783,12 +3783,17 @@ void
 ring_buffer_read_finish(struct ring_buffer_iter *iter)
 {
 	struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
+	unsigned long flags;
 
 	/*
 	 * Ring buffer is disabled from recording, here's a good place
-	 * to check the integrity of the ring buffer. 
+	 * to check the integrity of the ring buffer.
+	 * Must prevent readers from trying to read, as the check
+	 * clears the HEAD page and readers require it.
 	 */
+	raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
 	rb_check_pages(cpu_buffer);
+	raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
 
 	atomic_dec(&cpu_buffer->record_disabled);
 	atomic_dec(&cpu_buffer->buffer->resize_disabled);