[src/trunk]: src/sys/external/bsd/drm2/linux drm: Implement drm_resv_get_fenc...

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

details:   https://anonhg.NetBSD.org/src/rev/34e06b3ab4ac
branches:  trunk
changeset: 1028938:34e06b3ab4ac
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Sun Dec 19 12:31:34 2021 +0000

description:
drm: Implement drm_resv_get_fences_rcu with null fencep.

diffstat:

 sys/external/bsd/drm2/linux/linux_dma_resv.c |  30 ++++++++++++++++++++++-----
 1 files changed, 24 insertions(+), 6 deletions(-)

diffs (83 lines):

diff -r e976b1f8d8fe -r 34e06b3ab4ac sys/external/bsd/drm2/linux/linux_dma_resv.c
--- a/sys/external/bsd/drm2/linux/linux_dma_resv.c      Sun Dec 19 12:31:26 2021 +0000
+++ b/sys/external/bsd/drm2/linux/linux_dma_resv.c      Sun Dec 19 12:31:34 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: linux_dma_resv.c,v 1.16 2021/12/19 12:26:39 riastradh Exp $    */
+/*     $NetBSD: linux_dma_resv.c,v 1.17 2021/12/19 12:31:34 riastradh Exp $    */
 
 /*-
  * Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: linux_dma_resv.c,v 1.16 2021/12/19 12:26:39 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: linux_dma_resv.c,v 1.17 2021/12/19 12:31:34 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/poll.h>
@@ -745,6 +745,8 @@
  *     Get a snapshot of the exclusive and shared fences of robj.  The
  *     shared fences are returned as a pointer *sharedp to an array,
  *     to be freed by the caller with kfree, of *nsharedp elements.
+ *     If fencep is null, then add the exclusive fence, if any, at the
+ *     end of the array instead.
  *
  *     Returns zero on success, negative (Linux-style) error code on
  *     failure.  On failure, *fencep, *nsharedp, and *sharedp are
@@ -771,13 +773,24 @@
                goto restart;
        if (list != NULL) {
 
+               /*
+                * Avoid arithmetic overflow with `+ 1' below.
+                * Strictly speaking we don't need this if the caller
+                * specified fencep or if there is no exclusive fence,
+                * but it is simpler to not have to consider those
+                * cases.
+                */
+               KASSERT(shared_count <= list->shared_max);
+               if (list->shared_max == UINT_MAX)
+                       return -ENOMEM;
+
                /* Check whether we have a buffer.  */
                if (shared == NULL) {
                        /*
                         * We don't have a buffer yet.  Try to allocate
                         * one without waiting.
                         */
-                       shared_alloc = list->shared_max;
+                       shared_alloc = list->shared_max + 1;
                        shared = kcalloc(shared_alloc, sizeof(shared[0]),
                            GFP_NOWAIT);
                        if (shared == NULL) {
@@ -793,13 +806,13 @@
                                        return -ENOMEM;
                                goto top;
                        }
-               } else if (shared_alloc < list->shared_max) {
+               } else if (shared_alloc < list->shared_max + 1) {
                        /*
                         * We have a buffer but it's too small.  We're
                         * already racing in this case, so just back
                         * out and wait to allocate a bigger one.
                         */
-                       shared_alloc = list->shared_max;
+                       shared_alloc = list->shared_max + 1;
                        rcu_read_unlock();
                        kfree(shared);
                        shared = kcalloc(shared_alloc, sizeof(shared[0]),
@@ -838,7 +851,12 @@
 
        /* Success!  */
        rcu_read_unlock();
-       *fencep = fence;
+       if (fencep) {
+               *fencep = fence;
+       } else if (fence) {
+               KASSERT(shared_count < UINT_MAX);
+               shared[shared_count++] = fence;
+       }
        *nsharedp = shared_count;
        *sharedp = shared;
        return 0;