From 9a35743df691b0173ef5ef49cfb664e88e2fc9da Mon Sep 17 00:00:00 2001
From: Christian Helmuth <christian.helmuth@genode-labs.com>
Date: Fri, 20 Dec 2019 14:34:22 +0100
Subject: [PATCH] Mark packet-stream descriptor head/tail as volatile

`volatile` effectively prevents instruction reordering by the compiler
and fixes an issue with -O3 compiled components.

Note, this commit does not address further arguments regarding memory
barriers and volatile voiced in issue #693.

Issue #693
---
 repos/os/include/os/packet_stream.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/repos/os/include/os/packet_stream.h b/repos/os/include/os/packet_stream.h
index 77ae905bdb..ca43afa768 100644
--- a/repos/os/include/os/packet_stream.h
+++ b/repos/os/include/os/packet_stream.h
@@ -168,8 +168,8 @@ class Genode::Packet_descriptor_queue
 		 */
 		struct
 		{
-			unsigned          _head;
-			unsigned          _tail;
+			unsigned volatile _head;
+			unsigned volatile _tail;
 			PACKET_DESCRIPTOR _queue[QUEUE_SIZE];
 		};