As soon as we install fences, we should stop allocating memory
in order to prevent any potential deadlocks.

This is required later on, when we start adding support for
dma-fence annotations.

Signed-off-by: Maarten Lankhorst <maarten.lankho...@linux.intel.com>
Reviewed-by: Thomas Hellström <thomas.hellst...@linux.intel.com>
---
 .../gpu/drm/i915/gem/i915_gem_execbuffer.c    | 24 ++++++++++++++-----
 drivers/gpu/drm/i915/i915_active.c            | 20 ++++++++--------
 drivers/gpu/drm/i915/i915_vma.c               |  8 ++++---
 drivers/gpu/drm/i915/i915_vma.h               |  3 +++
 4 files changed, 36 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c 
b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 1938dd739454..b5056bd80464 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -50,11 +50,12 @@ enum {
 #define DBG_FORCE_RELOC 0 /* choose one of the above! */
 };
 
-#define __EXEC_OBJECT_HAS_PIN          BIT(31)
-#define __EXEC_OBJECT_HAS_FENCE                BIT(30)
-#define __EXEC_OBJECT_NEEDS_MAP                BIT(29)
-#define __EXEC_OBJECT_NEEDS_BIAS       BIT(28)
-#define __EXEC_OBJECT_INTERNAL_FLAGS   (~0u << 28) /* all of the above */
+/* __EXEC_OBJECT_NO_RESERVE is BIT(31), defined in i915_vma.h */
+#define __EXEC_OBJECT_HAS_PIN          BIT(30)
+#define __EXEC_OBJECT_HAS_FENCE                BIT(29)
+#define __EXEC_OBJECT_NEEDS_MAP                BIT(28)
+#define __EXEC_OBJECT_NEEDS_BIAS       BIT(27)
+#define __EXEC_OBJECT_INTERNAL_FLAGS   (~0u << 27) /* all of the above + */
 #define __EXEC_OBJECT_RESERVED (__EXEC_OBJECT_HAS_PIN | 
__EXEC_OBJECT_HAS_FENCE)
 
 #define __EXEC_HAS_RELOC       BIT(31)
@@ -928,6 +929,12 @@ static int eb_validate_vmas(struct i915_execbuffer *eb)
                        }
                }
 
+               if (!(ev->flags & EXEC_OBJECT_WRITE)) {
+                       err = dma_resv_reserve_shared(vma->resv, 1);
+                       if (err)
+                               return err;
+               }
+
                GEM_BUG_ON(drm_mm_node_allocated(&vma->node) &&
                           eb_vma_misplaced(&eb->exec[i], vma, ev->flags));
        }
@@ -2188,7 +2195,8 @@ static int eb_move_to_gpu(struct i915_execbuffer *eb)
                }
 
                if (err == 0)
-                       err = i915_vma_move_to_active(vma, eb->request, flags);
+                       err = i915_vma_move_to_active(vma, eb->request,
+                                                     flags | 
__EXEC_OBJECT_NO_RESERVE);
        }
 
        if (unlikely(err))
@@ -2440,6 +2448,10 @@ static int eb_parse_pipeline(struct i915_execbuffer *eb,
        if (err)
                goto err_commit;
 
+       err = dma_resv_reserve_shared(shadow->resv, 1);
+       if (err)
+               goto err_commit;
+
        /* Wait for all writes (and relocs) into the batch to complete */
        err = i915_sw_fence_await_reservation(&pw->base.chain,
                                              pw->batch->resv, NULL, false,
diff --git a/drivers/gpu/drm/i915/i915_active.c 
b/drivers/gpu/drm/i915/i915_active.c
index 3bc616cc1ad2..cf9a3d384971 100644
--- a/drivers/gpu/drm/i915/i915_active.c
+++ b/drivers/gpu/drm/i915/i915_active.c
@@ -293,18 +293,13 @@ static struct active_node *__active_lookup(struct 
i915_active *ref, u64 idx)
 static struct i915_active_fence *
 active_instance(struct i915_active *ref, u64 idx)
 {
-       struct active_node *node, *prealloc;
+       struct active_node *node;
        struct rb_node **p, *parent;
 
        node = __active_lookup(ref, idx);
        if (likely(node))
                return &node->base;
 
-       /* Preallocate a replacement, just in case */
-       prealloc = kmem_cache_alloc(global.slab_cache, GFP_KERNEL);
-       if (!prealloc)
-               return NULL;
-
        spin_lock_irq(&ref->tree_lock);
        GEM_BUG_ON(i915_active_is_idle(ref));
 
@@ -314,10 +309,8 @@ active_instance(struct i915_active *ref, u64 idx)
                parent = *p;
 
                node = rb_entry(parent, struct active_node, node);
-               if (node->timeline == idx) {
-                       kmem_cache_free(global.slab_cache, prealloc);
+               if (node->timeline == idx)
                        goto out;
-               }
 
                if (node->timeline < idx)
                        p = &parent->rb_right;
@@ -325,7 +318,14 @@ active_instance(struct i915_active *ref, u64 idx)
                        p = &parent->rb_left;
        }
 
-       node = prealloc;
+       /*
+        * XXX: We should preallocate this before i915_active_ref() is ever
+        *  called, but we cannot call into fs_reclaim() anyway, so use 
GFP_ATOMIC.
+        */
+       node = kmem_cache_alloc(global.slab_cache, GFP_ATOMIC);
+       if (!node)
+               goto out;
+
        __i915_active_fence_init(&node->base, NULL, node_retire);
        node->ref = ref;
        node->timeline = idx;
diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 7310893086f7..1ffda2aaa7a0 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -1247,9 +1247,11 @@ int i915_vma_move_to_active(struct i915_vma *vma,
                obj->write_domain = I915_GEM_DOMAIN_RENDER;
                obj->read_domains = 0;
        } else {
-               err = dma_resv_reserve_shared(vma->resv, 1);
-               if (unlikely(err))
-                       return err;
+               if (!(flags & __EXEC_OBJECT_NO_RESERVE)) {
+                       err = dma_resv_reserve_shared(vma->resv, 1);
+                       if (unlikely(err))
+                               return err;
+               }
 
                dma_resv_add_shared_fence(vma->resv, &rq->fence);
                obj->write_domain = 0;
diff --git a/drivers/gpu/drm/i915/i915_vma.h b/drivers/gpu/drm/i915/i915_vma.h
index 3c914c9de9a9..6b48f5c42488 100644
--- a/drivers/gpu/drm/i915/i915_vma.h
+++ b/drivers/gpu/drm/i915/i915_vma.h
@@ -52,6 +52,9 @@ static inline bool i915_vma_is_active(const struct i915_vma 
*vma)
        return !i915_active_is_idle(&vma->active);
 }
 
+/* do not reserve memory to prevent deadlocks */
+#define __EXEC_OBJECT_NO_RESERVE BIT(31)
+
 int __must_check __i915_vma_move_to_active(struct i915_vma *vma,
                                           struct i915_request *rq);
 int __must_check i915_vma_move_to_active(struct i915_vma *vma,
-- 
2.30.1

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