Module Name: src
Committed By: riastradh
Date: Sat Feb 25 00:33:39 UTC 2023
Modified Files:
src/sys/arch/xen/xen: xencons.c
Log Message:
xencons(4): Reduce unnecessary membars.
- xencons_handler: After advancing in_cons, only need one xen_wmb
before notifying the hypervisor that we're ready for more.
(XXX Should this do xen_mb and re-check in_prod at that point, or
does hypervisor_notify_via_evtchn obviate the need for this?)
- xenvonscn_getc: After reading in_prod, only need one xen_rmb before
using the slots it is telling us are now ready.
To generate a diff of this commit:
cvs rdiff -u -r1.51 -r1.52 src/sys/arch/xen/xen/xencons.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/xen/xen/xencons.c
diff -u src/sys/arch/xen/xen/xencons.c:1.51 src/sys/arch/xen/xen/xencons.c:1.52
--- src/sys/arch/xen/xen/xencons.c:1.51 Sat Feb 25 00:33:27 2023
+++ src/sys/arch/xen/xen/xencons.c Sat Feb 25 00:33:38 2023
@@ -1,4 +1,4 @@
-/* $NetBSD: xencons.c,v 1.51 2023/02/25 00:33:27 riastradh Exp $ */
+/* $NetBSD: xencons.c,v 1.52 2023/02/25 00:33:38 riastradh Exp $ */
/*
* Copyright (c) 2006 Manuel Bouyer.
@@ -53,7 +53,7 @@
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: xencons.c,v 1.51 2023/02/25 00:33:27 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: xencons.c,v 1.52 2023/02/25 00:33:38 riastradh Exp $");
#include "opt_xen.h"
@@ -479,9 +479,9 @@ xencons_handler(void *arg)
cons += len;
xen_wmb();
xencons_interface->in_cons = cons;
- xen_wmb();
}
}
+ xen_wmb();
hypervisor_notify_via_evtchn(xen_start_info.console.domU.evtchn);
splx(s);
return 1;
@@ -575,7 +575,6 @@ xenconscn_getc(dev_t dev)
cons = xencons_interface->in_cons;
prod = xencons_interface->in_prod;
- xen_rmb();
while (cons == prod) {
HYPERVISOR_yield();
prod = xencons_interface->in_prod;
