ring-buffer: do not swap buffers during a commit

If a commit is taking place on a CPU ring buffer, do not allow it to
be swapped. Return -EBUSY when this is detected instead.

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

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 79d6012..2878bd4 100644 (file)
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -3519,16 +3519,23 @@ int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
        atomic_inc(&cpu_buffer_a->record_disabled);
        atomic_inc(&cpu_buffer_b->record_disabled);
 
+       ret = -EBUSY;
+       if (local_read(&cpu_buffer_a->committing))
+               goto out_dec;
+       if (local_read(&cpu_buffer_b->committing))
+               goto out_dec;
+
        buffer_a->buffers[cpu] = cpu_buffer_b;
        buffer_b->buffers[cpu] = cpu_buffer_a;
 
        cpu_buffer_b->buffer = buffer_a;
        cpu_buffer_a->buffer = buffer_b;
 
+       ret = 0;
+
+out_dec:
        atomic_dec(&cpu_buffer_a->record_disabled);
        atomic_dec(&cpu_buffer_b->record_disabled);
-
-       ret = 0;
 out:
        return ret;
 }