Re: [igt-dev] [PATCH i-g-t v2 3/4] i915/gem_create: use atomic_* instead of __sync_*

["Ser, Simon" <simon.ser@intel.com>]

On Thu, 2019-06-13 at 14:53 +0100, Guillaume Tucker wrote:
> This fixes builds on some architectures, in particular MIPS which
> doesn't have __sync_add_and_fetch_8 and __sync_val_compare_and_swap_8
> for 64-bit variable handling.
> 
> * replace calls to the older __sync_* functions with the new atomic_*
>   standard ones
> * use the _Atomic type modifier as required with stdatomic.h functions
> * add dependency for gem_create on libatomic
> 
> Signed-off-by: Guillaume Tucker <guillaume.tucker@collabora.com>

LGTM!

Reviewed-by: Simon Ser <simon.ser@intel.com>

> ---
>  tests/Makefile.am       |  2 +-
>  tests/i915/gem_create.c | 16 ++++++++++++----
>  tests/meson.build       |  9 ++++++++-
>  3 files changed, 21 insertions(+), 6 deletions(-)
> 
> diff --git a/tests/Makefile.am b/tests/Makefile.am
> index 5a428b8ac213..bbd386c9c2db 100644
> --- a/tests/Makefile.am
> +++ b/tests/Makefile.am
> @@ -90,7 +90,7 @@ AM_LDFLAGS = -Wl,--as-needed
>  drm_import_export_CFLAGS = $(AM_CFLAGS) $(THREAD_CFLAGS)
>  drm_import_export_LDADD = $(LDADD) -lpthread
>  gem_create_CFLAGS = $(AM_CFLAGS) $(THREAD_CFLAGS)
> -gem_create_LDADD = $(LDADD) -lpthread
> +gem_create_LDADD = $(LDADD) -lpthread -latomic
>  gem_close_race_CFLAGS = $(AM_CFLAGS) $(THREAD_CFLAGS)
>  gem_close_race_LDADD = $(LDADD) -lpthread
>  gem_ctx_thrash_CFLAGS = $(AM_CFLAGS) $(THREAD_CFLAGS)
> diff --git a/tests/i915/gem_create.c b/tests/i915/gem_create.c
> index 43cbf45f289b..9008cd8a21e3 100644
> --- a/tests/i915/gem_create.c
> +++ b/tests/i915/gem_create.c
> @@ -45,6 +45,7 @@
>  #include <sys/time.h>
>  #include <getopt.h>
>  #include <pthread.h>
> +#include <stdatomic.h>
>  
>  #include <drm.h>
>  
> @@ -156,7 +157,14 @@ static void invalid_nonaligned_size(int fd)
>  	gem_close(fd, create.handle);
>  }
>  
> -static uint64_t get_npages(uint64_t *global, uint64_t npages)
> +static uint64_t atomic_compare_swap_u64(_Atomic(uint64_t) *ptr,
> +					uint64_t oldval, uint64_t newval)
> +{
> +	atomic_compare_exchange_strong(ptr, &oldval, newval);
> +	return oldval;
> +}
> +
> +static uint64_t get_npages(_Atomic(uint64_t) *global, uint64_t npages)
>  {
>  	uint64_t try, old, max;
>  
> @@ -165,13 +173,13 @@ static uint64_t get_npages(uint64_t *global, uint64_t npages)
>  		old = max;
>  		try = 1 + npages % (max / 2);
>  		max -= try;
> -	} while ((max = __sync_val_compare_and_swap(global, old, max)) != old);
> +	} while ((max = atomic_compare_swap_u64(global, old, max)) != old);
>  
>  	return try;
>  }
>  
>  struct thread_clear {
> -	uint64_t max;
> +	_Atomic(uint64_t) max;
>  	int timeout;
>  	int i915;
>  };
> @@ -202,7 +210,7 @@ static void *thread_clear(void *data)
>  		}
>  		gem_close(i915, create.handle);
>  
> -		__sync_add_and_fetch(&arg->max, npages);
> +		atomic_fetch_add(&arg->max, npages);
>  	}
>  
>  	return NULL;
> diff --git a/tests/meson.build b/tests/meson.build
> index f168fbbae2a8..ffd432d38193 100644
> --- a/tests/meson.build
> +++ b/tests/meson.build
> @@ -110,7 +110,6 @@ i915_progs = [
>  	'gem_close_race',
>  	'gem_concurrent_blit',
>  	'gem_cpu_reloc',
> -	'gem_create',
>  	'gem_cs_prefetch',
>  	'gem_cs_tlb',
>  	'gem_ctx_bad_destroy',
> @@ -277,6 +276,14 @@ foreach prog : i915_progs
>  	test_list += prog
>  endforeach
>  
> +test_executables += executable('gem_create',
> +	   join_paths('i915', 'gem_create.c'),
> +	   dependencies : test_deps + [ libatomic ],
> +	   install_dir : libexecdir,
> +	   install_rpath : libexecdir_rpathdir,
> +	   install : true)
> +test_list += 'gem_create'
> +
>  test_executables += executable('gem_ctx_sseu',
>  	   join_paths('i915', 'gem_ctx_sseu.c'),
>  	   dependencies : test_deps + [ lib_igt_perf ],
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