On Fri, Dec 09, 2016 at 04:52:32PM +0000, Chris Wilson wrote:
> With prime, we are running into false circular dependencies based on the
> order in which two drivers may lock their own struct_mutex wrt to a
> common lock (like the reservation->lock). Work around this by adding the
> lock_class_key to the struct drm_driver such that each driver can have
> its own subclass of struct_mutex. Circular dependencies between drivers
> will now be ignored, but real circular dependencies on any one mutex
> will still be caught. A driver creating more than one device will still
> need to be careful!
>
> Reported-by: Tobias Klausmann <tobias.johannes.klausmann@xxxxxxxxxx>
> Reported-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Where does this even happen? i915, msm and udl are the only drivers left
over that do struct_mutex, and i915 can't really share buffers with msm,
and udl doesn't do reservations. How exactly does this still go boom in
latest upstream?
-Daniel
> ---
> drivers/gpu/drm/drm_drv.c | 4 +++-
> include/drm/drm_drv.h | 6 ++++++
> 2 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 2fa4e4fa7c33..82b521146e71 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -488,7 +488,9 @@ int drm_dev_init(struct drm_device *dev,
>
> spin_lock_init(&dev->buf_lock);
> spin_lock_init(&dev->event_lock);
> - mutex_init(&dev->struct_mutex);
> + __mutex_init(&dev->struct_mutex,
> + "&dev->struct_mutex",
> + &driver->class.struct_mutex_key);
> mutex_init(&dev->filelist_mutex);
> mutex_init(&dev->ctxlist_mutex);
> mutex_init(&dev->master_mutex);
> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
> index 554104ccb939..5d521923404a 100644
> --- a/include/drm/drm_drv.h
> +++ b/include/drm/drm_drv.h
> @@ -39,6 +39,10 @@ struct dma_buf_attachment;
> struct drm_display_mode;
> struct drm_mode_create_dumb;
>
> +struct drm_driver_class {
> + struct lock_class_key struct_mutex_key;
> +};
> +
> /* driver capabilities and requirements mask */
> #define DRIVER_USE_AGP 0x1
> #define DRIVER_LEGACY 0x2
> @@ -64,6 +68,8 @@ struct drm_mode_create_dumb;
> * structure for GEM drivers.
> */
> struct drm_driver {
> + struct drm_driver_class class;
> +
> int (*load) (struct drm_device *, unsigned long flags);
> int (*firstopen) (struct drm_device *);
> int (*open) (struct drm_device *, struct drm_file *);
> --
> 2.11.0
>
> _______________________________________________
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> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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