tracing: Wake up waiters when tracing is disabled

commit 2b0fd9a59b7990c161fa1cb7b79edb22847c87c2 upstream.

When tracing is disabled, there's no reason that waiters should stay
waiting, wake them up, otherwise tasks get stuck when they should be
flushing the buffers.

Cc: stable@vger.kernel.org
Fixes: e30f53aad2202 ("tracing: Do not busy wait in buffer splice")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 5b553bd69b78db5b156c4e0625634b9bb49d1fee..a2bbaed05eaddf114f4b9b446c040431250606bc 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8334,6 +8334,10 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
                if (ret)
                        goto out;
 
+               /* No need to wait after waking up when tracing is off */
+               if (!tracer_tracing_is_on(iter->tr))
+                       goto out;
+
                /* Make sure we see the new wait_index */
                smp_rmb();
                if (wait_index != iter->wait_index)
@@ -9043,6 +9047,8 @@ rb_simple_write(struct file *filp, const char __user *ubuf,
                        tracer_tracing_off(tr);
                        if (tr->current_trace->stop)
                                tr->current_trace->stop(tr);
+                       /* Wake up any waiters */
+                       ring_buffer_wake_waiters(buffer, RING_BUFFER_ALL_CPUS);
                }
                mutex_unlock(&trace_types_lock);
        }