[Linaro-mm-sig] Re: [PATCH 4/6] drm/panthor: Use guards for resv locking

On Wed, May 13, 2026 at 10:09 AM Boris Brezillon boris.brezillon@collabora.com wrote:

Now that we have guards for resv locks, we can use them to simplify the core. The only manual lock/unlock remaining are the ones in panthor_gem_try_evict_no_resv_wait(), because the lock/unlock are in different for_each() loop scopes.

Signed-off-by: Boris Brezillon boris.brezillon@collabora.com

Reviewed-by: Chia-I Wu olvaffe@gmail.com

---

drivers/gpu/drm/panthor/panthor_gem.c | 77 ++++++++++++----------------------- drivers/gpu/drm/panthor/panthor_mmu.c | 16 ++++---- 2 files changed, 32 insertions(+), 61 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c index a6fddc380e7d..94facdc8cfe1 100644 --- a/drivers/gpu/drm/panthor/panthor_gem.c +++ b/drivers/gpu/drm/panthor/panthor_gem.c @@ -339,13 +339,9 @@ panthor_gem_dev_map_get_sgt_locked(struct panthor_gem_object *bo) struct sg_table * panthor_gem_get_dev_sgt(struct panthor_gem_object *bo) {

•   struct sg_table *sgt;
  

•   guard(dma_resv)(bo->base.resv);
  
  

•   dma_resv_lock(bo->base.resv, NULL);
  

•   sgt = panthor_gem_dev_map_get_sgt_locked(bo);
  

•   dma_resv_unlock(bo->base.resv);
  

•   return sgt;
  

•   return panthor_gem_dev_map_get_sgt_locked(bo);
  

}

static void @@ -497,7 +493,7 @@ panthor_gem_prime_begin_cpu_access(struct dma_buf *dma_buf, struct panthor_gem_object *bo = to_panthor_bo(obj); struct dma_buf_attachment *attach;

•   dma_resv_lock(obj->resv, NULL);
  

•   guard(dma_resv)(obj->resv);
    if (bo->dmap.sgt)
            dma_sync_sgtable_for_cpu(drm_dev_dma_dev(dev), bo->dmap.sgt, dir);
  
  

@@ -510,7 +506,6 @@ panthor_gem_prime_begin_cpu_access(struct dma_buf *dma_buf, if (sgt) dma_sync_sgtable_for_cpu(attach->dev, sgt, dir); }

•   dma_resv_unlock(obj->resv);
  
    return 0;
  

} @@ -524,7 +519,7 @@ panthor_gem_prime_end_cpu_access(struct dma_buf *dma_buf, struct panthor_gem_object *bo = to_panthor_bo(obj); struct dma_buf_attachment *attach;

•   dma_resv_lock(obj->resv, NULL);
  

•   guard(dma_resv)(obj->resv);
    list_for_each_entry(attach, &dma_buf->attachments, node) {
            struct sg_table *sgt = attach->priv;
  
  

@@ -538,7 +533,6 @@ panthor_gem_prime_end_cpu_access(struct dma_buf *dma_buf, if (bo->dmap.sgt) dma_sync_sgtable_for_device(drm_dev_dma_dev(dev), bo->dmap.sgt, dir);

•   dma_resv_unlock(obj->resv);
    return 0;
  

}

@@ -625,19 +619,15 @@ static void panthor_gem_unpin_locked(struct drm_gem_object *obj)

int panthor_gem_pin(struct panthor_gem_object *bo) {

•   int ret = 0;
  

•   if (drm_gem_is_imported(&bo->base))
            return 0;
  
    if (refcount_inc_not_zero(&bo->backing.pin_count))
            return 0;
  
  

•   dma_resv_lock(bo->base.resv, NULL);
  

•   ret = panthor_gem_backing_pin_locked(bo);
  

•   dma_resv_unlock(bo->base.resv);
  

•   guard(dma_resv)(bo->base.resv);
  
  

•   return ret;
  

•   return panthor_gem_backing_pin_locked(bo);
  

}

void panthor_gem_unpin(struct panthor_gem_object *bo) @@ -648,9 +638,8 @@ void panthor_gem_unpin(struct panthor_gem_object *bo) if (refcount_dec_not_one(&bo->backing.pin_count)) return;

•   dma_resv_lock(bo->base.resv, NULL);
  

•   guard(dma_resv)(bo->base.resv);
    panthor_gem_backing_unpin_locked(bo);
  

•   dma_resv_unlock(bo->base.resv);
  

}

int panthor_gem_swapin_locked(struct panthor_gem_object *bo) @@ -759,13 +748,12 @@ static int panthor_gem_mmap(struct drm_gem_object *obj, struct vm_area_struct *v return -EINVAL;

    if (!refcount_inc_not_zero(&bo->cmap.mmap_count)) {

•           dma_resv_lock(obj->resv, NULL);
  

•           guard(dma_resv)(obj->resv);
            if (!refcount_inc_not_zero(&bo->cmap.mmap_count)) {
                    refcount_set(&bo->cmap.mmap_count, 1);
                    guard(mutex)(&bo->base.gpuva.lock);
                    panthor_gem_update_reclaim_state_locked(bo, NULL);
            }
  

•           dma_resv_unlock(obj->resv);
    }
  
    vm_flags_set(vma, VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
  

@@ -814,18 +802,12 @@ static vm_fault_t nonblocking_page_setup(struct vm_fault *vmf, { struct vm_area_struct *vma = vmf->vma; struct panthor_gem_object *bo = to_panthor_bo(vma->vm_private_data);

•   vm_fault_t ret;
  
  

•   if (!dma_resv_trylock(bo->base.resv))
  

•   ACQUIRE(dma_resv_try, resv_guard)(bo->base.resv);
  

•   if (ACQUIRE_ERR(dma_resv_try, &resv_guard) || !bo->backing.pages)
            return VM_FAULT_RETRY;
  
  

•   if (bo->backing.pages)
  

•           ret = insert_page(vmf, order, bo->backing.pages[page_offset]);
  

•   else
  

•           ret = VM_FAULT_RETRY;
  

•   dma_resv_unlock(bo->base.resv);
  

•   return ret;
  

•   return insert_page(vmf, order, bo->backing.pages[page_offset]);
  

}

static vm_fault_t blocking_page_setup(struct vm_fault *vmf, unsigned int order, @@ -835,8 +817,8 @@ static vm_fault_t blocking_page_setup(struct vm_fault *vmf, unsigned int order, vm_fault_t ret; int err;

•   err = dma_resv_lock_interruptible(bo->base.resv, NULL);
  

•   if (err)
  

•   ACQUIRE(dma_resv_intr, resv_guard)(bo->base.resv);
  

•   if (ACQUIRE_ERR(dma_resv_intr, &resv_guard))
            return mmap_lock_held ? VM_FAULT_NOPAGE : VM_FAULT_RETRY;
  
    err = panthor_gem_backing_get_pages_locked(bo);
  

@@ -857,8 +839,6 @@ static vm_fault_t blocking_page_setup(struct vm_fault *vmf, unsigned int order, ret = VM_FAULT_RETRY; }

•   dma_resv_unlock(bo->base.resv);
  

•   return ret;
  

}

@@ -932,12 +912,12 @@ static void panthor_gem_vm_close(struct vm_area_struct *vma) if (refcount_dec_not_one(&bo->cmap.mmap_count)) goto out;

•   dma_resv_lock(bo->base.resv, NULL);
  

•   if (refcount_dec_and_test(&bo->cmap.mmap_count)) {
  

•           guard(mutex)(&bo->base.gpuva.lock);
  

•           panthor_gem_update_reclaim_state_locked(bo, NULL);
  

•   scoped_guard(dma_resv, bo->base.resv) {
  

•           if (refcount_dec_and_test(&bo->cmap.mmap_count)) {
  

•                   guard(mutex)(&bo->base.gpuva.lock);
  

•                   panthor_gem_update_reclaim_state_locked(bo, NULL);
  

•           }
    }
  

•   dma_resv_unlock(bo->base.resv);
  
  

out: drm_gem_object_put(&bo->base); @@ -1161,21 +1141,18 @@ panthor_gem_sync(struct drm_gem_object *obj, u32 type, if (size == 0) return 0;

•   ret = dma_resv_lock_interruptible(bo->base.resv, NULL);
  

•   ACQUIRE(dma_resv_intr, resv_guard)(bo->base.resv);
  

•   ret = ACQUIRE_ERR(dma_resv_intr, &resv_guard);
    if (ret)
            return ret;
  
    /* If there's no pages, there's no point pulling those back, bail out early. */
  

•   if (!bo->backing.pages) {
  

•           ret = 0;
  

•           goto out_unlock;
  

•   }
  

•   if (!bo->backing.pages)
  

•           return 0;
  
    sgt = panthor_gem_dev_map_get_sgt_locked(bo);
  

•   if (IS_ERR(sgt)) {
  

•           ret = PTR_ERR(sgt);
  

•           goto out_unlock;
  

•   }
  

•   if (IS_ERR(sgt))
  

•           return PTR_ERR(sgt);
  
    for_each_sgtable_dma_sg(sgt, sgl, count) {
            if (size == 0)
  

@@ -1219,11 +1196,7 @@ panthor_gem_sync(struct drm_gem_object *obj, u32 type, dma_sync_single_for_cpu(dma_dev, paddr, len, DMA_FROM_DEVICE); }

•   ret = 0;
  

-out_unlock:

•   dma_resv_unlock(bo->base.resv);
  

•   return ret;
  

•   return 0;
  

}

/** diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c index 157eef286cb9..ab9a77e6a145 100644 --- a/drivers/gpu/drm/panthor/panthor_mmu.c +++ b/drivers/gpu/drm/panthor/panthor_mmu.c @@ -1118,10 +1118,10 @@ static void panthor_vm_bo_free(struct drm_gpuvm_bo *vm_bo) /* We couldn't call this when we unlinked, because the resv lock can't * be taken in the dma signalling path, so call it now. */

•   dma_resv_lock(bo->base.resv, NULL);
  

•   scoped_guard(mutex, &bo->base.gpuva.lock)
  

•   scoped_guard(dma_resv, bo->base.resv) {
  

•           guard(mutex)(&bo->base.gpuva.lock);
            panthor_gem_update_reclaim_state_locked(bo, NULL);
  

•   dma_resv_unlock(bo->base.resv);
  

•   }
  
    kfree(vm_bo);
  

} @@ -1342,16 +1342,14 @@ static int panthor_vm_prepare_map_op_ctx(struct panthor_vm_op_ctx *op_ctx,

    /* Insert BO into the extobj list last, when we know nothing can fail. */
    if (bo->base.resv != panthor_vm_resv(vm)) {

•           dma_resv_lock(panthor_vm_resv(vm), NULL);
  

•           guard(dma_resv)(panthor_vm_resv(vm));
            drm_gpuvm_bo_extobj_add(op_ctx->map.vm_bo);
  

•           dma_resv_unlock(panthor_vm_resv(vm));
    }
  
    /* And finally update the BO state. */
  

•   dma_resv_lock(bo->base.resv, NULL);
  

•   scoped_guard(mutex, &bo->base.gpuva.lock)
  

•           panthor_gem_update_reclaim_state_locked(bo, NULL);
  

•   dma_resv_unlock(bo->base.resv);
  

•   guard(dma_resv)(bo->base.resv);
  

•   guard(mutex)(&bo->base.gpuva.lock);
  

•   panthor_gem_update_reclaim_state_locked(bo, NULL);
  
    return 0;
  
  
  

-- 2.54.0