linux-kernel - Re: [PATCH 1/2] drm/exec: use unique instead of local label

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Message-ID: <20230731180020.4c47e0e3@collabora.com>
Date:   Mon, 31 Jul 2023 18:00:20 +0200
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Christian König <ckoenig.leichtzumerken@...il.com>,
        ndesaulniers@...gle.com, maarten.lankhorst@...ux.intel.com,
        mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com,
        daniel@...ll.ch, trix@...hat.com, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        naresh.kamboju@...aro.org, dakr@...hat.com
Subject: Re: [PATCH 1/2] drm/exec: use unique instead of local label

On Mon, 31 Jul 2023 08:31:19 -0700
Nathan Chancellor <nathan@...nel.org> wrote:

> On Mon, Jul 31, 2023 at 02:36:24PM +0200, Christian König 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@...nel.org>
> > Reported-by: Naresh Kamboju <naresh.kamboju@...aro.org>
> > CC: Boris Brezillon <boris.brezillon@...labora.com>

Reviewed-by: Boris Brezillon <boris.brezillon@...labora.com>

> > Signed-off-by: Christian König <christian.koenig@....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@...nel.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
> > 
> >