Hi,
On 27/03/18 11:23, Daniel Vetter wrote:
> The only thing that omap_gem_free_object does that might need the
> magic protection of struct_mutex (of keeping all objects alive if that
> lock is held, even if the last reference is gone) is the mm_list
> manipulation.
>
> But that is already protected by the separate omapdrm->list_lock,
> which means struct_mutex is an entirely internal lock for omapdrm.
> Everything else is just releasing resources, which is all protected
> already by the various subsystems and allocators.
>
> To make this even more obvious we could do an
> s/dev->struct_mutex/omapdrm->gem_lock/ like I've done for udl. But
> since omapdrm is a lot bigger and a lot more active I'll refrain from
> that - this is better done by omapdrm developers at some suitable time
> in the future.
>
> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> Cc: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
> ---
> drivers/gpu/drm/omapdrm/omap_drv.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/omapdrm/omap_drv.c b/drivers/gpu/drm/omapdrm/omap_drv.c
> index 3f40f7af3285..6d52877ed25a 100644
> --- a/drivers/gpu/drm/omapdrm/omap_drv.c
> +++ b/drivers/gpu/drm/omapdrm/omap_drv.c
> @@ -490,7 +490,7 @@ static struct drm_driver omap_drm_driver = {
> .prime_fd_to_handle = drm_gem_prime_fd_to_handle,
> .gem_prime_export = omap_gem_prime_export,
> .gem_prime_import = omap_gem_prime_import,
> - .gem_free_object = omap_gem_free_object,
> + .gem_free_object_unlocked = omap_gem_free_object,
> .gem_vm_ops = &omap_gem_vm_ops,
> .dumb_create = omap_gem_dumb_create,
> .dumb_map_offset = omap_gem_dumb_map_offset,
>
This triggers WARN_ON(!mutex_is_locked(&dev->struct_mutex)), we have a
few of those. I need to reverse engineer the omap_gem locking a bit to
understand what's needed. And I need to figure out what exactly does
struct_mutext protect =).
Tomi
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