target/linux/brcm2708/patches-4.4/0096-drm-vc4-Drop-struct_mutex-around-CL-validation.patch

   1 From 08d3b4a8535a142d79c30fe6a558ac8c97de11f1 Mon Sep 17 00:00:00 2001
   2 From: Eric Anholt <eric@anholt.net>
   3 Date: Mon, 19 Oct 2015 08:44:35 -0700
   4 Subject: [PATCH] drm/vc4: Drop struct_mutex around CL validation.
   5
   6 We were using it so that we could make sure that shader validation
   7 state didn't change while we were validating, but now shader
   8 validation state is immutable.  The bcl/rcl generation doesn't do any
   9 other BO dereferencing, and seems to have no other global state
  10 dependency not covered by job_lock / bo_lock.  We only need to hold
  11 struct_mutex for object unreferencing.
  12
  13 Fixes a lock order reversal between mmap_sem and struct_mutex.
  14
  15 Signed-off-by: Eric Anholt <eric@anholt.net>
  16 ---
  17  drivers/gpu/drm/vc4/vc4_gem.c | 13 ++++++-------
  18  1 file changed, 6 insertions(+), 7 deletions(-)
  19
  20 --- a/drivers/gpu/drm/vc4/vc4_gem.c
  21 +++ b/drivers/gpu/drm/vc4/vc4_gem.c
  22 @@ -439,10 +439,12 @@ fail:
  23  }
  24
  25  static void
  26 -vc4_complete_exec(struct vc4_exec_info *exec)
  27 +vc4_complete_exec(struct drm_device *dev, struct vc4_exec_info *exec)
  28  {
  29         unsigned i;
  30
  31 +       /* Need the struct lock for drm_gem_object_unreference(). */
  32 +       mutex_lock(&dev->struct_mutex);
  33         if (exec->bo) {
  34                 for (i = 0; i < exec->bo_count; i++)
  35                         drm_gem_object_unreference(&exec->bo[i].bo->base);
  36 @@ -455,6 +457,7 @@ vc4_complete_exec(struct vc4_exec_info *
  37                 list_del(&bo->unref_head);
  38                 drm_gem_object_unreference(&bo->base.base);
  39         }
  40 +       mutex_unlock(&dev->struct_mutex);
  41
  42         kfree(exec);
  43  }
  44 @@ -473,7 +476,7 @@ vc4_job_handle_completed(struct vc4_dev
  45                 list_del(&exec->head);
  46
  47                 spin_unlock_irqrestore(&vc4->job_lock, irqflags);
  48 -               vc4_complete_exec(exec);
  49 +               vc4_complete_exec(vc4->dev, exec);
  50                 spin_lock_irqsave(&vc4->job_lock, irqflags);
  51         }
  52
  53 @@ -525,12 +528,8 @@ vc4_job_done_work(struct work_struct *wo
  54  {
  55         struct vc4_dev *vc4 =
  56                 container_of(work, struct vc4_dev, job_done_work);
  57 -       struct drm_device *dev = vc4->dev;
  58
  59 -       /* Need the struct lock for drm_gem_object_unreference(). */
  60 -       mutex_lock(&dev->struct_mutex);
  61         vc4_job_handle_completed(vc4);
  62 -       mutex_unlock(&dev->struct_mutex);
  63  }
  64
  65  static int
  66 @@ -639,7 +638,7 @@ vc4_submit_cl_ioctl(struct drm_device *d
  67         return 0;
  68
  69  fail:
  70 -       vc4_complete_exec(exec);
  71 +       vc4_complete_exec(vc4->dev, exec);
  72
  73         return ret;
  74  }