drm/radeon: fix vm deadlocks on cayman

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@vodafone.de>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

diff --git a/drivers/gpu/drm/radeon/radeon_gart.c b/drivers/gpu/drm/radeon/radeon_gart.c
index 79db56e..59d4493 100644 (file)
--- 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);