On 8/10/20 12:30 PM, Maarten Lankhorst wrote:
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, and also required for userptr.

Signed-off-by: Maarten Lankhorst <maarten.lankho...@linux.intel.com>
---
  drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 18 ++++++++++++------
  drivers/gpu/drm/i915/i915_vma.c                |  8 +++++---
  drivers/gpu/drm/i915/i915_vma.h                |  3 +++
  3 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c 
b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 5d08ce71f341..12397fbc0971 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -48,11 +48,12 @@ 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 */

Hmm. Could we either move all these flag definitions to a header or add an i915_vma_move_to_active()?


+#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)
@@ -2094,7 +2095,8 @@ 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))
@@ -2291,6 +2293,10 @@ 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_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index c6bf04ca2032..8066f167d6b9 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -1227,9 +1227,11 @@ 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 d0d01f909548..4b325a670a04 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,
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