On Thu, Oct 10, 2013 at 8:22 PM, Thomas Hellstrom <thellstrom@xxxxxxxxxx> wrote:
> Make use of the FAULT_FLAG_ALLOW_RETRY flag to allow dropping the
> mmap_sem while waiting for bo idle.
>
> FAULT_FLAG_ALLOW_RETRY appears to be primarily designed for disk waits
> but should work just as fine for GPU waits..
>
> Signed-off-by: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
Reviewed-by: Jakob Bornecrantz <jakob@xxxxxxxxxx>
Tho somebody else should also take a look at this.
> ---
> drivers/gpu/drm/ttm/ttm_bo_vm.c | 62 +++++++++++++++++++++++++++++++--------
> 1 file changed, 50 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> index 1006c15..c03514b 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> @@ -41,6 +41,51 @@
>
> #define TTM_BO_VM_NUM_PREFAULT 16
>
> +static int ttm_bo_vm_fault_idle(struct ttm_buffer_object *bo,
> + struct vm_area_struct *vma,
> + struct vm_fault *vmf)
> +{
> + struct ttm_bo_device *bdev = bo->bdev;
> + int ret = 0;
> +
> + spin_lock(&bdev->fence_lock);
> + if (likely(!test_bit(TTM_BO_PRIV_FLAG_MOVING, &bo->priv_flags)))
> + goto out_unlock;
> +
> + /*
> + * Quick non-stalling check for idle.
> + */
> + ret = ttm_bo_wait(bo, false, false, true);
> + if (likely(ret == 0))
> + goto out_unlock;
> +
> + /*
> + * If possible, avoid waiting for GPU with mmap_sem
> + * held.
> + */
> + if (vmf->flags & FAULT_FLAG_ALLOW_RETRY) {
> + ret = VM_FAULT_RETRY;
> + if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
> + goto out_unlock;
> +
> + up_read(&vma->vm_mm->mmap_sem);
> + (void) ttm_bo_wait(bo, false, true, false);
> + goto out_unlock;
> + }
> +
> + /*
> + * Ordinary wait.
> + */
> + ret = ttm_bo_wait(bo, false, true, false);
> + if (unlikely(ret != 0))
> + ret = (ret != -ERESTARTSYS) ? VM_FAULT_SIGBUS :
> + VM_FAULT_NOPAGE;
> +
> +out_unlock:
> + spin_unlock(&bdev->fence_lock);
> + return ret;
> +}
> +
> static int ttm_bo_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
> {
> struct ttm_buffer_object *bo = (struct ttm_buffer_object *)
> @@ -91,18 +136,11 @@ static int ttm_bo_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
> * Wait for buffer data in transit, due to a pipelined
> * move.
> */
> -
> - spin_lock(&bdev->fence_lock);
> - if (test_bit(TTM_BO_PRIV_FLAG_MOVING, &bo->priv_flags)) {
> - ret = ttm_bo_wait(bo, false, true, false);
> - spin_unlock(&bdev->fence_lock);
> - if (unlikely(ret != 0)) {
> - retval = (ret != -ERESTARTSYS) ?
> - VM_FAULT_SIGBUS : VM_FAULT_NOPAGE;
> - goto out_unlock;
> - }
> - } else
> - spin_unlock(&bdev->fence_lock);
> + ret = ttm_bo_vm_fault_idle(bo, vma, vmf);
> + if (unlikely(ret != 0)) {
> + retval = ret;
> + goto out_unlock;
> + }
>
> ret = ttm_mem_io_lock(man, true);
> if (unlikely(ret != 0)) {
> --
> 1.7.10.4
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