anv/allocator: Avoid race condition in anv_block_pool_map.

Accessing bo->map and then pool->center_bo_offset without a lock is
racy. One way of avoiding such race condition is to store the bo->map +
center_bo_offset into pool->map at the time the block pool is growing,
which happens within a lock.

v2: Only set pool->map if not using softpin (Jason).
v3: Move things around and only update center_bo_offset if not using
softpin too (Jason).

Cc: Jason Ekstrand <[email protected]>
Reported-by: Ian Romanick <[email protected]>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109442
Fixes: fc3f58832015cbb177179e7f3420d3611479b4a9
Reviewed-by: Jason Ekstrand <[email protected]>

1 files changed, 13 insertions, 0 deletions

diff --git a/src/intel/vulkan/anv_private.h b/src/intel/vulkan/anv_private.h
index 3889065c93c..110b2ccf023 100644
--- a/src/intel/vulkan/anv_private.h
+++ b/src/intel/vulkan/anv_private.h
@@ -663,6 +663,19 @@ struct anv_block_pool {
     */
    uint32_t center_bo_offset;
 
+   /* Current memory map of the block pool.  This pointer may or may not
+    * point to the actual beginning of the block pool memory.  If
+    * anv_block_pool_alloc_back has ever been called, then this pointer
+    * will point to the "center" position of the buffer and all offsets
+    * (negative or positive) given out by the block pool alloc functions
+    * will be valid relative to this pointer.
+    *
+    * In particular, map == bo.map + center_offset
+    *
+    * DO NOT access this pointer directly. Use anv_block_pool_map() instead,
+    * since it will handle the softpin case as well, where this points to NULL.
+    */
+   void *map;
    int fd;
 
    /**