[src/trunk]: src/sys/external/bsd/drm2/linux drm: dma_fence_get allows fence ...

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

details:   https://anonhg.NetBSD.org/src/rev/2254cdfb60a9
branches:  trunk
changeset: 1028861:2254cdfb60a9
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Sun Dec 19 12:13:45 2021 +0000

description:
drm: dma_fence_get allows fence to be null; fix assertion.

While here, update comments about semantics for dma_fence_get and
dma_fence_get_rcu (which does not allow null fence).

diffstat:

 sys/external/bsd/drm2/linux/linux_dma_fence.c |  17 ++++++++++-------
 1 files changed, 10 insertions(+), 7 deletions(-)

diffs (53 lines):

diff -r 104dfca8674f -r 2254cdfb60a9 sys/external/bsd/drm2/linux/linux_dma_fence.c
--- a/sys/external/bsd/drm2/linux/linux_dma_fence.c     Sun Dec 19 12:13:37 2021 +0000
+++ b/sys/external/bsd/drm2/linux/linux_dma_fence.c     Sun Dec 19 12:13:45 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: linux_dma_fence.c,v 1.25 2021/12/19 12:11:05 riastradh Exp $   */
+/*     $NetBSD: linux_dma_fence.c,v 1.26 2021/12/19 12:13:45 riastradh Exp $   */
 
 /*-
  * Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: linux_dma_fence.c,v 1.25 2021/12/19 12:11:05 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: linux_dma_fence.c,v 1.26 2021/12/19 12:13:45 riastradh Exp $");
 
 #include <sys/atomic.h>
 #include <sys/condvar.h>
@@ -246,18 +246,21 @@
 /*
  * dma_fence_get(fence)
  *
- *     Acquire a reference to fence.  The fence must not be being
- *     destroyed.  Return the fence.
+ *     Acquire a reference to fence and return it, or return NULL if
+ *     fence is NULL.  The fence, if nonnull, must not be being
+ *     destroyed.
  */
 struct dma_fence *
 dma_fence_get(struct dma_fence *fence)
 {
 
+       if (fence == NULL)
+               return NULL;
+
        KASSERTMSG(fence->f_magic != FENCE_MAGIC_BAD, "fence %p", fence);
        KASSERTMSG(fence->f_magic == FENCE_MAGIC_GOOD, "fence %p", fence);
 
-       if (fence)
-               kref_get(&fence->refcount);
+       kref_get(&fence->refcount);
        return fence;
 }
 
@@ -266,7 +269,7 @@
  *
  *     Attempt to acquire a reference to a fence that may be about to
  *     be destroyed, during a read section.  Return the fence on
- *     success, or NULL on failure.
+ *     success, or NULL on failure.  The fence must be nonnull.
  */
 struct dma_fence *
 dma_fence_get_rcu(struct dma_fence *fence)