Mesa (master): util/sparse_array: don't stomp head's counter on pop operations

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Module: Mesa
Branch: master
Commit: dc3a17997b479f91f36b2421e9c41c11a025de47
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=dc3a17997b479f91f36b2421e9c41c11a025de47

Author: D Scott Phillips <d.scott.phillips at intel.com>
Date:   Fri Apr 17 10:28:06 2020 -0700

util/sparse_array: don't stomp head's counter on pop operations

By temporarily storing the new_head by a uint32_t, we wipe out the
counter section of the head pointer.

Fixes: e4f01eca ("util: Add a free list structure for use with util_sparse_array")
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
Reviewed-by: Rafael Antognolli <rafael.antognolli at intel.com>
Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4612>

---

 src/util/sparse_array.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/util/sparse_array.c b/src/util/sparse_array.c
index 61dbd2acdff..0c04fd0d6dc 100644
--- a/src/util/sparse_array.c
+++ b/src/util/sparse_array.c
@@ -270,7 +270,7 @@ util_sparse_array_free_list_pop_idx(struct util_sparse_array_free_list *fl)
       uint32_t head_idx = current_head; /* Index is the bottom 32 bits */
       void *head_elem = util_sparse_array_get(fl->arr, head_idx);
       uint32_t *head_next = (uint32_t *)((char *)head_elem + fl->next_offset);
-      uint32_t new_head = free_list_head(current_head, *head_next);
+      uint64_t new_head = free_list_head(current_head, *head_next);
       uint64_t old_head = p_atomic_cmpxchg(&fl->head, current_head, new_head);
       if (old_head == current_head)
          return head_idx;
@@ -291,7 +291,7 @@ util_sparse_array_free_list_pop_elem(struct util_sparse_array_free_list *fl)
       uint32_t head_idx = current_head; /* Index is the bottom 32 bits */
       void *head_elem = util_sparse_array_get(fl->arr, head_idx);
       uint32_t *head_next = (uint32_t *)((char *)head_elem + fl->next_offset);
-      uint32_t new_head = free_list_head(current_head, *head_next);
+      uint64_t new_head = free_list_head(current_head, *head_next);
       uint64_t old_head = p_atomic_cmpxchg(&fl->head, current_head, new_head);
       if (old_head == current_head)
          return head_elem;