Re: [PATCH 5/5] drm/omapdrm: Switch to gem_free_object_unlocked

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

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@intel.com>
> Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
> ---
>  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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