linux-kernel - Re: [PATCH v3 07/10] perf: Cleanup for HAVE_SYNC_COMPARE_AND_SWAP

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Date:   Sun, 11 Jul 2021 16:08:00 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 07/10] perf: Cleanup for
 HAVE_SYNC_COMPARE_AND_SWAP_SUPPORT

Hi Adrian,

On Sat, Jul 10, 2021 at 03:36:53PM +0300, Adrian Hunter wrote:
> 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?

There are files are still using __sync_xxx_compare_and_swap() functions,
e.g. in the folder tools/testing/selftests/bpf.  On the other hand,
after drop __sync functions from perf, there have no any Makefile check
the feature 'feature-sync-compare-and-swap'.  So it's safe to remove the
feature test.

Sorry for confusion.  Will drop the feature test in new patch set.

Thanks,
Leo