[PATCH] drm/radeon: fix vm deadlocks on cayman

[Jerome Glisse]

On Sun, Jun 3, 2012 at 10:09 AM, Christian König
<deathsimple at vodafone.de> wrote:
> Locking mutex in different orders just screams for
> deadlocks, and some testing showed that it is actually
> quite easy to trigger them.
>
> Signed-off-by: Christian König <deathsimple at vodafone.de>
Reviewed-by: Jerome Glisse <jglisse at redhat.com>

> Cc: stable at vger.kernel.org
> ---
>  drivers/gpu/drm/radeon/radeon_gart.c |   19 ++++++++++++-------
>  1 file changed, 12 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/radeon/radeon_gart.c b/drivers/gpu/drm/radeon/radeon_gart.c
> index 79db56e..59d4493 100644
> --- a/drivers/gpu/drm/radeon/radeon_gart.c
> +++ b/drivers/gpu/drm/radeon/radeon_gart.c
> @@ -476,12 +476,18 @@ int radeon_vm_bo_add(struct radeon_device *rdev,
>
>        mutex_lock(&vm->mutex);
>        if (last_pfn > vm->last_pfn) {
> -               /* grow va space 32M by 32M */
> -               unsigned align = ((32 << 20) >> 12) - 1;
> +               /* release mutex and lock in right order */
> +               mutex_unlock(&vm->mutex);
>                radeon_mutex_lock(&rdev->cs_mutex);
> -               radeon_vm_unbind_locked(rdev, vm);
> +               mutex_lock(&vm->mutex);
> +               /* and check again */
> +               if (last_pfn > vm->last_pfn) {
> +                       /* grow va space 32M by 32M */
> +                       unsigned align = ((32 << 20) >> 12) - 1;
> +                       radeon_vm_unbind_locked(rdev, vm);
> +                       vm->last_pfn = (last_pfn + align) & ~align;
> +               }
>                radeon_mutex_unlock(&rdev->cs_mutex);
> -               vm->last_pfn = (last_pfn + align) & ~align;
>        }
>        head = &vm->va;
>        last_offset = 0;
> @@ -595,8 +601,8 @@ int radeon_vm_bo_rmv(struct radeon_device *rdev,
>        if (bo_va == NULL)
>                return 0;
>
> -       mutex_lock(&vm->mutex);
>        radeon_mutex_lock(&rdev->cs_mutex);
> +       mutex_lock(&vm->mutex);
>        radeon_vm_bo_update_pte(rdev, vm, bo, NULL);
>        radeon_mutex_unlock(&rdev->cs_mutex);
>        list_del(&bo_va->vm_list);
> @@ -641,9 +647,8 @@ void radeon_vm_fini(struct radeon_device *rdev, struct radeon_vm *vm)
>        struct radeon_bo_va *bo_va, *tmp;
>        int r;
>
> -       mutex_lock(&vm->mutex);
> -
>        radeon_mutex_lock(&rdev->cs_mutex);
> +       mutex_lock(&vm->mutex);
>        radeon_vm_unbind_locked(rdev, vm);
>        radeon_mutex_unlock(&rdev->cs_mutex);
>
> --
> 1.7.9.5
>
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