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nvidia-drm: defer nv_drm_device free until final DRM reference #1336

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nvidia-drm: defer nv_drm_device free until final DRM reference #1336

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46 changes: 45 additions & 1 deletion kernel-open/nvidia-drm/nvidia-drm-drv.c
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Original file line number Diff line number Diff line change
Expand Up @@ -95,6 +95,7 @@
#include <drm/drm_gem.h>
#include <drm/drm_auth.h>
#include <drm/drm_atomic_helper.h>
#include <drm/drm_managed.h>

static int nv_drm_revoke_modeset_permission(struct drm_device *dev,
struct drm_file *filep,
Expand Down Expand Up @@ -2015,6 +2016,22 @@ void nv_drm_update_drm_driver_features(void)



/*
* nv_drm_device is referenced by userspace-visible DRM/GEM/fence objects
* which may outlive drm_dev_unplug(). Keep it alive until the DRM device's
* final reference is released.
*/
static void nv_drm_dev_private_release(struct drm_device *dev, void *data)
{
struct nv_drm_device *nv_dev = data;

if (dev->dev_private == nv_dev) {
dev->dev_private = NULL;
}

nv_drm_free(nv_dev);
}

/*
* Helper function for allocate/register DRM device for given NVIDIA GPU ID.
*/
Expand Down Expand Up @@ -2056,6 +2073,22 @@ void nv_drm_register_drm_device(const struct NvKmsKapiGpuInfo *gpu_info)
dev->dev_private = nv_dev;
nv_dev->dev = dev;

/*
* drm_dev_unplug() does not imply that all userspace DRM files are closed.
* GEM/fence teardown from those files still dereferences nv_dev, so make
* nv_dev a DRM-managed resource and free it only on the final drm_dev_put().
*/
if (drmm_add_action(dev, nv_drm_dev_private_release, nv_dev) != 0) {
NV_DRM_DEV_LOG_ERR(
nv_dev,
"Failed to register DRM-managed nv_drm_device cleanup");
dev->dev_private = NULL;
nv_dev->dev = NULL;
drm_dev_put(dev);
nv_drm_free(nv_dev);
return;
}

bus_is_pci =
#if defined(NV_LINUX)
device->bus == &pci_bus_type;
Expand Down Expand Up @@ -2155,10 +2188,16 @@ void nv_drm_register_drm_device(const struct NvKmsKapiGpuInfo *gpu_info)

failed_drm_load:

/*
* The DRM-managed release action frees nv_dev when this is the final
* drm_dev_put(). Do not fall through and free it a second time.
*/
drm_dev_put(dev);
return;

failed_drm_alloc:

/* drm_dev_alloc() failed, so no managed release action exists. */
nv_drm_free(nv_dev);
}

Expand Down Expand Up @@ -2230,8 +2269,13 @@ static void nv_drm_dev_destroy(struct nv_drm_device *nv_dev)
struct drm_device *dev = nv_dev->dev;

nv_drm_dev_unload(dev);

/*
* Drop the driver's DRM reference. Open userspace files may still hold
* references; nv_drm_device is freed by nv_drm_dev_private_release()
* only after the final one disappears.
*/
drm_dev_put(dev);
nv_drm_free(nv_dev);
}

/*
Expand Down