[src/trunk]: src/sys/external/bsd/drm2/linux Clarify with comments and assert...

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

details:   https://anonhg.NetBSD.org/src/rev/b8341cfa9dbe
branches:  trunk
changeset: 992948:b8341cfa9dbe
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Mon Aug 27 14:14:13 2018 +0000

description:
Clarify with comments and assertions.

diffstat:

 sys/external/bsd/drm2/linux/linux_reservation.c |  15 +++++++++++++--
 1 files changed, 13 insertions(+), 2 deletions(-)

diffs (45 lines):

diff -r 48506a8edeec -r b8341cfa9dbe sys/external/bsd/drm2/linux/linux_reservation.c
--- a/sys/external/bsd/drm2/linux/linux_reservation.c   Mon Aug 27 14:13:46 2018 +0000
+++ b/sys/external/bsd/drm2/linux/linux_reservation.c   Mon Aug 27 14:14:13 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: linux_reservation.c,v 1.6 2018/08/27 14:13:46 riastradh Exp $  */
+/*     $NetBSD: linux_reservation.c,v 1.7 2018/08/27 14:14:13 riastradh Exp $  */
 
 /*-
  * Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: linux_reservation.c,v 1.6 2018/08/27 14:13:46 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: linux_reservation.c,v 1.7 2018/08/27 14:14:13 riastradh Exp $");
 
 #include <linux/fence.h>
 #include <linux/reservation.h>
@@ -390,6 +390,11 @@
 
        /* Check for a preallocated replacement list.  */
        if (prealloc == NULL) {
+               /*
+                * If there is no preallocated replacement list, then
+                * there must be room in the current list.
+                */
+               KASSERT(list != NULL);
                KASSERT(list->shared_count < list->shared_max);
 
                /* Begin an update.  */
@@ -411,8 +416,14 @@
                /* Commit the update.  */
                reservation_object_write_commit(robj, &ticket);
        } else {
+               /*
+                * There is a preallocated replacement list.  There may
+                * not be a current list.  If not, treat it as a zero-
+                * length list.
+                */
                uint32_t shared_count = (list == NULL? 0 : list->shared_count);
 
+               /* There had better be room in the preallocated list.  */
                KASSERT(shared_count < prealloc->shared_max);
 
                /*