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Date:   Mon, 31 Jul 2023 08:31:19 -0700
From:   Nathan Chancellor <nathan@kernel.org>
To:     Christian =?iso-8859-1?Q?K=F6nig?= 
        <ckoenig.leichtzumerken@gmail.com>
Cc:     boris.brezillon@collabora.com, ndesaulniers@google.com,
        maarten.lankhorst@linux.intel.com, mripard@kernel.org,
        tzimmermann@suse.de, airlied@gmail.com, daniel@ffwll.ch,
        trix@redhat.com, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org, llvm@lists.linux.dev,
        naresh.kamboju@linaro.org, dakr@redhat.com
Subject: Re: [PATCH 1/2] drm/exec: use unique instead of local label
Message-ID: <20230731153119.GA773004@dev-arch.thelio-3990X>
References: <20230731123625.3766-1-christian.koenig@amd.com>
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In-Reply-To: <20230731123625.3766-1-christian.koenig@amd.com>
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On Mon, Jul 31, 2023 at 02:36:24PM +0200, Christian K?nig wrote:
> GCC forbids to jump to labels in loop conditions and a new clang
> check stumbled over this.
> 
> So instead using a local label inside the loop condition use an
> unique label outside of it.
> 
> Fixes: commit 09593216bff1 ("drm: execution context for GEM buffers v7")
> Link: https://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html
> Link: https://github.com/ClangBuiltLinux/linux/issues/1890
> Link: https://github.com/llvm/llvm-project/commit/20219106060208f0c2f5d096eb3aed7b712f5067
> Reported-by: Nathan Chancellor <nathan@kernel.org>
> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
> CC: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Christian K?nig <christian.koenig@amd.com>

Passes my build tests and I inspected the preprocessed output to make
sure it should work. I ran the KUnit tests, which all pass (although [1]
is needed to fix a tangential issue):

Tested-by: Nathan Chancellor <nathan@kernel.org>

Thanks for fixing this!

[1]: https://lore.kernel.org/20230728183400.306193-1-arthurgrillo@riseup.net/

> ---
>  include/drm/drm_exec.h | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/include/drm/drm_exec.h b/include/drm/drm_exec.h
> index 73205afec162..e0462361adf9 100644
> --- a/include/drm/drm_exec.h
> +++ b/include/drm/drm_exec.h
> @@ -3,6 +3,7 @@
>  #ifndef __DRM_EXEC_H__
>  #define __DRM_EXEC_H__
>  
> +#include <linux/compiler.h>
>  #include <linux/ww_mutex.h>
>  
>  #define DRM_EXEC_INTERRUPTIBLE_WAIT	BIT(0)
> @@ -74,13 +75,12 @@ struct drm_exec {
>   * Since labels can't be defined local to the loops body we use a jump pointer
>   * to make sure that the retry is only used from within the loops body.
>   */
> -#define drm_exec_until_all_locked(exec)				\
> -	for (void *__drm_exec_retry_ptr; ({			\
> -		__label__ __drm_exec_retry;			\
> -__drm_exec_retry:						\
> -		__drm_exec_retry_ptr = &&__drm_exec_retry;	\
> -		(void)__drm_exec_retry_ptr;			\
> -		drm_exec_cleanup(exec);				\
> +#define drm_exec_until_all_locked(exec)					\
> +__PASTE(__drm_exec_, __LINE__):						\
> +	for (void *__drm_exec_retry_ptr; ({				\
> +		__drm_exec_retry_ptr = &&__PASTE(__drm_exec_, __LINE__);\
> +		(void)__drm_exec_retry_ptr;				\
> +		drm_exec_cleanup(exec);					\
>  	});)
>  
>  /**
> -- 
> 2.34.1
> 
>