drm/imagination: Break an object reference loop

When remaining resources are being cleaned up on driver close,
outstanding VM mappings may result in resources being leaked, due
to an object reference loop, as shown below, with each object (or
set of objects) referencing the object below it:

    PVR GEM Object
    GPU scheduler "finished" fence
    GPU scheduler “scheduled” fence
    PVR driver “done” fence
    PVR Context
    PVR VM Context
    PVR VM Mappings
    PVR GEM Object

The reference that the PVR VM Context has on the VM mappings is a
soft one, in the sense that the freeing of outstanding VM mappings
is done as part of VM context destruction; no reference counts are
involved, as is the case for all the other references in the loop.

To break the reference loop during cleanup, free the outstanding
VM mappings before destroying the PVR Context associated with the
VM context.

Signed-off-by: Brendan King <brendan.king@imgtec.com>
Signed-off-by: Matt Coster <matt.coster@imgtec.com>
Reviewed-by: Frank Binns <frank.binns@imgtec.com>
Cc: stable@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/8a25924f-1bb7-4d9a-a346-58e871dfb1d1@imgtec.com

diff --git a/drivers/gpu/drm/imagination/pvr_context.c b/drivers/gpu/drm/imagination/pvr_context.c
index 255c93582734a8f78e87a9f432f907cfb7fe788c..4cb3494c0bb2c6ca00425b801710e427c9dcf9bd 100644 (file)
--- a/drivers/gpu/drm/imagination/pvr_context.c
+++ b/drivers/gpu/drm/imagination/pvr_context.c
@@ -450,11 +450,30 @@ pvr_context_destroy(struct pvr_file *pvr_file, u32 handle)
  */
 void pvr_destroy_contexts_for_file(struct pvr_file *pvr_file)
 {
+       struct pvr_device *pvr_dev = pvr_file->pvr_dev;
        struct pvr_context *ctx;
        unsigned long handle;
 
        xa_for_each(&pvr_file->ctx_handles, handle, ctx)
                pvr_context_destroy(pvr_file, handle);
+
+       spin_lock(&pvr_dev->ctx_list_lock);
+       ctx = list_first_entry(&pvr_file->contexts, struct pvr_context, file_link);
+
+       while (!list_entry_is_head(ctx, &pvr_file->contexts, file_link)) {
+               list_del_init(&ctx->file_link);
+
+               if (pvr_context_get_if_referenced(ctx)) {
+                       spin_unlock(&pvr_dev->ctx_list_lock);
+
+                       pvr_vm_unmap_all(ctx->vm_ctx);
+
+                       pvr_context_put(ctx);
+                       spin_lock(&pvr_dev->ctx_list_lock);
+               }
+               ctx = list_first_entry(&pvr_file->contexts, struct pvr_context, file_link);
+       }
+       spin_unlock(&pvr_dev->ctx_list_lock);
 }
 
 /**

diff --git a/drivers/gpu/drm/imagination/pvr_context.h b/drivers/gpu/drm/imagination/pvr_context.h
index a5b0a82a54a1d3f50c42916659b0240765000927..07afa179cdf421c0adc258640fac9595a0059023 100644 (file)
--- a/drivers/gpu/drm/imagination/pvr_context.h
+++ b/drivers/gpu/drm/imagination/pvr_context.h
@@ -126,6 +126,24 @@ pvr_context_get(struct pvr_context *ctx)
        return ctx;
 }
 
+/**
+ * pvr_context_get_if_referenced() - Take an additional reference on a still
+ * referenced context.
+ * @ctx: Context pointer.
+ *
+ * Call pvr_context_put() to release.
+ *
+ * Returns:
+ *  * True on success, or
+ *  * false if no context pointer passed, or the context wasn't still
+ *  * referenced.
+ */
+static __always_inline bool
+pvr_context_get_if_referenced(struct pvr_context *ctx)
+{
+       return ctx != NULL && kref_get_unless_zero(&ctx->ref_count) != 0;
+}
+
 /**
  * pvr_context_lookup() - Lookup context pointer from handle and file.
  * @pvr_file: Pointer to pvr_file structure.

diff --git a/drivers/gpu/drm/imagination/pvr_vm.c b/drivers/gpu/drm/imagination/pvr_vm.c
index 97c0f772ed65f20bb0013bcef5bac55751daf719..7bd6ba4c6e8ab6c81e45d46887e612710276d089 100644 (file)
--- a/drivers/gpu/drm/imagination/pvr_vm.c
+++ b/drivers/gpu/drm/imagination/pvr_vm.c
@@ -14,6 +14,7 @@
 #include <drm/drm_gem.h>
 #include <drm/drm_gpuvm.h>
 
+#include <linux/bug.h>
 #include <linux/container_of.h>
 #include <linux/err.h>
 #include <linux/errno.h>
@@ -597,12 +598,26 @@ err_free:
 }
 
 /**
- * pvr_vm_context_release() - Teardown a VM context.
- * @ref_count: Pointer to reference counter of the VM context.
+ * pvr_vm_unmap_all() - Unmap all mappings associated with a VM context.
+ * @vm_ctx: Target VM context.
  *
  * This function ensures that no mappings are left dangling by unmapping them
  * all in order of ascending device-virtual address.
  */
+void
+pvr_vm_unmap_all(struct pvr_vm_context *vm_ctx)
+{
+       WARN_ON(pvr_vm_unmap(vm_ctx, vm_ctx->gpuvm_mgr.mm_start,
+                            vm_ctx->gpuvm_mgr.mm_range));
+}
+
+/**
+ * pvr_vm_context_release() - Teardown a VM context.
+ * @ref_count: Pointer to reference counter of the VM context.
+ *
+ * This function also ensures that no mappings are left dangling by calling
+ * pvr_vm_unmap_all.
+ */
 static void
 pvr_vm_context_release(struct kref *ref_count)
 {
@@ -612,8 +627,7 @@ pvr_vm_context_release(struct kref *ref_count)
        if (vm_ctx->fw_mem_ctx_obj)
                pvr_fw_object_destroy(vm_ctx->fw_mem_ctx_obj);
 
-       WARN_ON(pvr_vm_unmap(vm_ctx, vm_ctx->gpuvm_mgr.mm_start,
-                            vm_ctx->gpuvm_mgr.mm_range));
+       pvr_vm_unmap_all(vm_ctx);
 
        pvr_mmu_context_destroy(vm_ctx->mmu_ctx);
        drm_gem_private_object_fini(&vm_ctx->dummy_gem);

diff --git a/drivers/gpu/drm/imagination/pvr_vm.h b/drivers/gpu/drm/imagination/pvr_vm.h
index f2a6463f2b059ed70f88fe27a4db9b9be8292748..79406243617c1f025c0119eb8deeaa13c0415586 100644 (file)
--- a/drivers/gpu/drm/imagination/pvr_vm.h
+++ b/drivers/gpu/drm/imagination/pvr_vm.h
@@ -39,6 +39,7 @@ int pvr_vm_map(struct pvr_vm_context *vm_ctx,
               struct pvr_gem_object *pvr_obj, u64 pvr_obj_offset,
               u64 device_addr, u64 size);
 int pvr_vm_unmap(struct pvr_vm_context *vm_ctx, u64 device_addr, u64 size);
+void pvr_vm_unmap_all(struct pvr_vm_context *vm_ctx);
 
 dma_addr_t pvr_vm_get_page_table_root_addr(struct pvr_vm_context *vm_ctx);
 struct dma_resv *pvr_vm_get_dma_resv(struct pvr_vm_context *vm_ctx);