[PATCH 5.15 113/530] tracing: Wake up waiters when tracing is disabled

[Greg Kroah-Hartman]

From: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>

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@xxxxxxxxxxxxxxx
Fixes: e30f53aad2202 ("tracing: Do not busy wait in buffer splice")
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 kernel/trace/trace.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8291,6 +8291,10 @@ tracing_buffers_splice_read(struct file
 		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)
@@ -9000,6 +9004,8 @@ rb_simple_write(struct file *filp, const
 			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);
 	}