[src/trunk]: src/sys/external/bsd/drm2/linux drm: Use KM_SLEEP to allocate re...

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

details:   https://anonhg.NetBSD.org/src/rev/66f437d29b96
branches:  trunk
changeset: 361581:66f437d29b96
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Tue Feb 15 22:51:03 2022 +0000

description:
drm: Use KM_SLEEP to allocate reservation fence arrays.

Except as a fast path in an RCU reader.

The array sizes appear to be reasonably small and not trivially
controlled by userland, from what I can tell, so if my impression is
accurate, it is reasonable to sleep for allocation here.

diffstat:

 sys/external/bsd/drm2/linux/linux_dma_resv.c |  48 +++++++++++++++++++--------
 1 files changed, 33 insertions(+), 15 deletions(-)

diffs (106 lines):

diff -r 3391e650d1ea -r 66f437d29b96 sys/external/bsd/drm2/linux/linux_dma_resv.c
--- a/sys/external/bsd/drm2/linux/linux_dma_resv.c      Tue Feb 15 22:46:53 2022 +0000
+++ b/sys/external/bsd/drm2/linux/linux_dma_resv.c      Tue Feb 15 22:51:03 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: linux_dma_resv.c,v 1.21 2021/12/19 12:36:02 riastradh Exp $    */
+/*     $NetBSD: linux_dma_resv.c,v 1.22 2022/02/15 22:51:03 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 1.21 2021/12/19 12:36:02 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: linux_dma_resv.c,v 1.22 2022/02/15 22:51:03 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/poll.h>
@@ -56,6 +56,17 @@
        return list;
 }
 
+static struct dma_resv_list *
+objlist_alloc(uint32_t n)
+{
+       struct dma_resv_list *list;
+
+       list = kmem_alloc(offsetof(typeof(*list), shared[n]), KM_SLEEP);
+       list->shared_max = n;
+
+       return list;
+}
+
 static void
 objlist_free(struct dma_resv_list *list)
 {
@@ -346,9 +357,7 @@
 
                /* Try to double its capacity.  */
                nalloc = n > UINT32_MAX/2 ? UINT32_MAX : 2*n;
-               prealloc = objlist_tryalloc(nalloc);
-               if (prealloc == NULL)
-                       return -ENOMEM;
+               prealloc = objlist_alloc(nalloc);
 
                /* Swap the new preallocated list and free the old one.  */
                objlist_free(robj->robj_prealloc);
@@ -356,9 +365,8 @@
        } else {
                /* Start with some spare.  */
                nalloc = n > UINT32_MAX/2 ? UINT32_MAX : MAX(2*n, 4);
-               prealloc = objlist_tryalloc(nalloc);
-               if (prealloc == NULL)
-                       return -ENOMEM;
+               prealloc = objlist_alloc(nalloc);
+
                /* Save the new preallocated list.  */
                robj->robj_prealloc = prealloc;
        }
@@ -689,8 +697,10 @@
                prealloc->shared_count = shared_count;
 
                /* If we didn't find one, add it at the end.  */
-               if (replace == NULL)
+               if (replace == NULL) {
+                       KASSERT(prealloc->shared_count < prealloc->shared_max);
                        prealloc->shared[prealloc->shared_count++] = fence;
+               }
 
                /*
                 * Now ready to replace the list.  Begin an update.
@@ -919,11 +929,20 @@
        if (!dma_resv_get_shared_reader(src_robj, &src_list, &shared_count,
                &read_ticket))
                goto restart;
-       if (src_list != NULL) {
-               /* Allocate a new list.  */
-               dst_list = objlist_tryalloc(shared_count);
+       if (src_list) {
+               /* Allocate a new list, if necessary.  */
                if (dst_list == NULL)
-                       return -ENOMEM;
+                       dst_list = objlist_tryalloc(shared_count);
+               if (dst_list == NULL || dst_list->shared_max < shared_count) {
+                       rcu_read_unlock();
+                       if (dst_list) {
+                               objlist_free(dst_list);
+                               dst_list = NULL;
+                       }
+                       dst_list = objlist_alloc(shared_count);
+                       dst_list->shared_count = 0; /* paranoia */
+                       goto top;
+               }
 
                /* Copy over all fences that are not yet signalled.  */
                dst_list->shared_count = 0;
@@ -1005,8 +1024,7 @@
                        dma_fence_put(dst_list->shared[i]);
                        dst_list->shared[i] = NULL; /* paranoia */
                }
-               objlist_free(dst_list);
-               dst_list = NULL;
+               /* reuse dst_list allocation for the next attempt */
        }
        goto top;
 }