From: David van Moolenbroek <david@minix3.org>
Date: Wed, 15 Jul 2015 01:10:35 +0000 (+0200)
Subject: libsys: add Tomas Hruby's asynsend barrier
X-Git-Url: http://zhaoyanbai.com/repos/%22http:/www.isc.org/icons/verify-sign/tz-link.htm?a=commitdiff_plain;h=a082b2af624583a7e2dda1ea970e55c5dcade0d3;p=minix.git

libsys: add Tomas Hruby's asynsend barrier

This barrier ensures that all fields of an asynchronously sent
message are properly initialized before the message is marked as
valid.

Change-Id: I7b9590c11c4e040c8f992f1dd2581e54201bf214
---

diff --git a/minix/lib/libsys/asynsend.c b/minix/lib/libsys/asynsend.c
index 3f414712f..d6c19eecd 100644
--- a/minix/lib/libsys/asynsend.c
+++ b/minix/lib/libsys/asynsend.c
@@ -126,6 +126,7 @@ int fl;
   fl |= AMF_VALID;	/* Mark in use */
   msgtable[next_slot].dst = dst;
   msgtable[next_slot].msg = *mp;
+  __insn_barrier();
   msgtable[next_slot].flags = fl;		/* Has to be last. The kernel 
 					 	 * scans this table while we
 						 * are sleeping.