Re: linux-next: build failure after merge of the rcu tree

[Daniel Vetter]

On Wed, Mar 08, 2017 at 12:16:45PM +1100, Stephen Rothwell wrote:
> Hi Paul,
> 
> After merging the rcu tree, today's linux-next build (x86_64 allmodconfig)
> failed like this:
> 
> In file included from include/linux/resource_ext.h:19:0,
>                  from include/linux/pci.h:32,
>                  from include/drm/drmP.h:50,
>                  from drivers/gpu/drm/i915/i915_gem.c:28:
> drivers/gpu/drm/i915/selftests/mock_gem_device.c: In function 'mock_gem_device':
> drivers/gpu/drm/i915/selftests/mock_gem_device.c:177:9: error: 'SLAB_DESTROY_BY_RCU' undeclared (first use in this function)
>          SLAB_DESTROY_BY_RCU);
>          ^
> include/linux/slab.h:149:4: note: in definition of macro 'KMEM_CACHE'
>    (__flags), NULL)
>     ^
> drivers/gpu/drm/i915/selftests/mock_gem_device.c:177:9: note: each undeclared identifier is reported only once for each function it appears in
>          SLAB_DESTROY_BY_RCU);
>          ^
> include/linux/slab.h:149:4: note: in definition of macro 'KMEM_CACHE'
>    (__flags), NULL)
>     ^
> /
> 
> Caused by commit
> 
>   24b7cb25b8d1 ("mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU")

Awesome rename. Count us in among the people who first thought this
provides more guarantees than it does.

> interacting with commit
> 
>   0daf0113cff6 ("drm/i915: Mock infrastructure for request emission")
> 
> from the drm-intel tree.
> 
> I added the following merge fix patch:
> 
> From: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> Date: Wed, 8 Mar 2017 12:09:49 +1100
> Subject: [PATCH] drm/i915: merge fix for "mm: Rename SLAB_DESTROY_BY_RCU to
>  SLAB_TYPESAFE_BY_RCU"
> 
> Signed-off-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>

Should we handle this with a topic branch? It's trivial to resolve, but I
fear the note that this conflict exists might get lost somewhere between
now and when the drm pull lands in Linus' inbox in 2 months ...

Otoh he's probably going to compile test drm extra carefully and will
notice :-)
-Daniel

> ---
>  drivers/gpu/drm/i915/selftests/mock_gem_device.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/selftests/mock_gem_device.c b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
> index 6a8258eacdcb..9f24c5da3f8d 100644
> --- a/drivers/gpu/drm/i915/selftests/mock_gem_device.c
> +++ b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
> @@ -174,7 +174,7 @@ struct drm_i915_private *mock_gem_device(void)
>  	i915->requests = KMEM_CACHE(mock_request,
>  				    SLAB_HWCACHE_ALIGN |
>  				    SLAB_RECLAIM_ACCOUNT |
> -				    SLAB_DESTROY_BY_RCU);
> +				    SLAB_TYPESAFE_BY_RCU);
>  	if (!i915->requests)
>  		goto err_vmas;
>  
> -- 
> 2.11.0
> 
> -- 
> Cheers,
> Stephen Rothwell

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch