Re: [PATCH v3 07/10] perf: Cleanup for HAVE_SYNC_COMPARE_AND_SWAP_SUPPORT

From: Adrian Hunter <adrian.hunter@intel.com>
To: Leo Yan <leo.yan@linaro.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Mathieu Poirier <mathieu.poirier@linaro.org>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Mike Leach <mike.leach@linaro.org>,
	linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
	coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 07/10] perf: Cleanup for HAVE_SYNC_COMPARE_AND_SWAP_SUPPORT
Date: Sat, 10 Jul 2021 15:36:53 +0300	[thread overview]
Message-ID: <86cd5d3d-2441-2f8e-28ab-54802e47c68b@intel.com> (raw)
In-Reply-To: <20210704071644.107397-8-leo.yan@linaro.org>

On 4/07/21 10:16 am, Leo Yan wrote:
> Since the __sync functions have been dropped, This patch removes unused
> build and checking for HAVE_SYNC_COMPARE_AND_SWAP_SUPPORT in perf tool.
> 
> Note, there have a test for SYNC_COMPARE_AND_SWAP and the test file is
> located in build/feature/test-sync-compare-and-swap.c.  Since there
> still has several components using the sync functions, it's deliberately
> to not be removed.

I don't quite follow that.  If they aren't using the feature test
macro, then why keep the feature test?

> 
>   $ cd linux/tools
>   $ git grep __sync_val_compare_and_swap | awk '{ printf $1"\n" }'
>   build/feature/test-sync-compare-and-swap.c:
>   include/asm-generic/atomic-gcc.h:
>   testing/selftests/bpf/progs/atomics.c:
>   testing/selftests/bpf/progs/atomics.c:
>   testing/selftests/bpf/progs/atomics.c:
>   testing/selftests/bpf/progs/atomics.c:
>   testing/selftests/futex/include/atomic.h:
>   testing/selftests/futex/include/futextest.h:
> 
> Signed-off-by: Leo Yan <leo.yan@linaro.org>
> ---
>  tools/perf/Makefile.config | 4 ----
>  tools/perf/util/auxtrace.c | 5 -----
>  2 files changed, 9 deletions(-)
> 
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index eb8e487ef90b..4a0d9a6defc7 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -349,10 +349,6 @@ CXXFLAGS += $(INC_FLAGS)
>  
>  LIBPERF_CFLAGS := $(CORE_CFLAGS) $(EXTRA_CFLAGS)
>  
> -ifeq ($(feature-sync-compare-and-swap), 1)
> -  CFLAGS += -DHAVE_SYNC_COMPARE_AND_SWAP_SUPPORT
> -endif
> -
>  ifeq ($(feature-pthread-attr-setaffinity-np), 1)
>    CFLAGS += -DHAVE_PTHREAD_ATTR_SETAFFINITY_NP
>  endif
> diff --git a/tools/perf/util/auxtrace.c b/tools/perf/util/auxtrace.c
> index 44bd04dbb6d6..db6255b55c90 100644
> --- a/tools/perf/util/auxtrace.c
> +++ b/tools/perf/util/auxtrace.c
> @@ -130,11 +130,6 @@ int auxtrace_mmap__mmap(struct auxtrace_mmap *mm,
>  		return 0;
>  	}
>  
> -#if BITS_PER_LONG != 64 && !defined(HAVE_SYNC_COMPARE_AND_SWAP_SUPPORT)
> -	pr_err("Cannot use AUX area tracing mmaps\n");
> -	return -1;
> -#endif
> -
>  	pc->aux_offset = mp->offset;
>  	pc->aux_size = mp->len;
>  
> 