ring-buffer: Move resize integrity check under reader lock

While using an application that does splice on the ftrace ring
buffer at start up, I triggered an integrity check failure.

Looking into this, I discovered that resizing the buffer performs
an integrity check after the buffer is resized. This check unfortunately
is preformed after it releases the reader lock. If a reader is
reading the buffer it may cause the integrity check to trigger a
false failure.

This patch simply moves the integrity checker under the protection
of the ring buffer reader lock.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 0d64c51..eccb4cf 100644 (file)
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1208,9 +1208,9 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
                return;
 
        rb_reset_cpu(cpu_buffer);
-       spin_unlock_irq(&cpu_buffer->reader_lock);
-
        rb_check_pages(cpu_buffer);
+
+       spin_unlock_irq(&cpu_buffer->reader_lock);
 }
 
 static void
@@ -1233,9 +1233,9 @@ rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
                list_add_tail(&bpage->list, cpu_buffer->pages);
        }
        rb_reset_cpu(cpu_buffer);
-       spin_unlock_irq(&cpu_buffer->reader_lock);
-
        rb_check_pages(cpu_buffer);
+
+       spin_unlock_irq(&cpu_buffer->reader_lock);
 }
 
 /**