[src/trunk]: src/sys/arch/i386/i386 It looks like Xen cpu_hatch() calls cpu_s...

[ad <ad%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/551675e8d763
branches:  trunk
changeset: 968356:551675e8d763
user:      ad <ad%NetBSD.org@localhost>
date:      Mon Jan 13 12:03:41 2020 +0000

description:
It looks like Xen cpu_hatch() calls cpu_switchto() with prevlwp=NULL,
instead of calling idle_loop() directly.  I can't test a change to
cpu_hatch() right now so allow for prevlwp=NULL.

diffstat:

 sys/arch/i386/i386/locore.S |  8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diffs (33 lines):

diff -r 4046617ea071 -r 551675e8d763 sys/arch/i386/i386/locore.S
--- a/sys/arch/i386/i386/locore.S       Mon Jan 13 11:53:24 2020 +0000
+++ b/sys/arch/i386/i386/locore.S       Mon Jan 13 12:03:41 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: locore.S,v 1.175 2020/01/08 17:38:41 ad Exp $  */
+/*     $NetBSD: locore.S,v 1.176 2020/01/13 12:03:41 ad Exp $  */
 
 /*
  * Copyright-o-rama!
@@ -128,7 +128,7 @@
  */
 
 #include <machine/asm.h>
-__KERNEL_RCSID(0, "$NetBSD: locore.S,v 1.175 2020/01/08 17:38:41 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: locore.S,v 1.176 2020/01/13 12:03:41 ad Exp $");
 
 #include "opt_copy_symtab.h"
 #include "opt_ddb.h"
@@ -1316,10 +1316,14 @@
        movl    20(%esp),%edi           /* newlwp */
        movl    24(%esp),%edx           /* returning */
 
+       testl   %esi,%esi               /* oldlwp = NULL ? */
+       jz      skip_save
+
        /* Save old context. */
        movl    L_PCB(%esi),%eax
        movl    %esp,PCB_ESP(%eax)
        movl    %ebp,PCB_EBP(%eax)
+skip_save:
 
        /* Switch to newlwp's stack. */
        movl    L_PCB(%edi),%ebx