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Message-ID: <a2c46546-b828-353b-4b70-826a614b1594@huawei.com>
Date:   Tue, 22 Mar 2022 22:17:36 +0000
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Subject: Re: perf version issues
To:     Arnaldo Carvalho de Melo <acme@kernel.org>
CC:     Ian Rogers <irogers@google.com>, Jiri Olsa <jolsa@kernel.org>,
        "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
        <linux-perf-users@vger.kernel.org>
References: <8a75f3b1-2b99-1233-3a70-070311b6ebc1@huawei.com>
 <YjotZExyiwhnX6ev@kernel.org>
From:   John Garry <john.garry@huawei.com>
In-Reply-To: <YjotZExyiwhnX6ev@kernel.org>
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On 22/03/2022 20:11, Arnaldo Carvalho de Melo wrote:
>> I have been finding that during my development that the output from "perf
>> -v" may be incorrect in certain circumstances. I sent some patches to fix it
>> up:
>> https://lore.kernel.org/linux-perf-users/1645449409-158238-1-git-send-email-john.garry@huawei.com/T/#mf7234d2e331a53370c148eb4a0633d405a5c6832
>>
>> Is there some issue that these cannot be processed?
> So, while testing it I noticed that if we use 'git cherry-pick' it
> doesn't trigger a rebuild, even having a new head:-\
> 
> I.e. with the two patches in at the HEAD, try:
> 
>    $ git log --oneline -2
>    cb66befccba18fac (HEAD -> perf/core) perf tools: Fix version kernel tag
>    4e666cdb06eede20 perf tools: Fix dependency for version file creation
>    $ make -C tools/perf O=/tmp/build/perf install-bin
>    $ perf -v
>    perf version 5.17.rc8.gcb66befccba1
> 
> Ok so far, now lets remove HEAD and leave just the first patch, that has
> the ORIG_HEAD dependency to trigger a rebuild:
> 
>    $ git reset --hard HEAD~
>    HEAD is now at 4e666cdb06eede20 perf tools: Fix dependency for version file creation
>    $ make -C tools/perf O=/tmp/build/perf install-bin
>    $ perf -v
>    perf version 5.17.rc8.g4e666cdb06ee
> 
> Ok, detected and rebuilt, perf -v works as expected.

ok, good

> 
> Now lets try cherry picking your second patch:
> 
> $ git cherry-pick cb66befccba18fac
>    [perf/core 8ff6a6c06a90a362] perf tools: Fix version kernel tag
>     Author: John Garry<john.garry@huawei.com>
>     Date: Mon Feb 21 21:16:49 2022 +0800
>     1 file changed, 4 insertions(+), 9 deletions(-)
>    $ make -C tools/perf O=/tmp/build/perf install-bin
>    $ perf -v
>    perf version 5.17.rc8.g4e666cdb06ee
> 
> Now it doesn´t notice it and there is no automatic rebuild triggered, we
> stay with the cset from before the cherry-pick:-\
> 
> $ git log --oneline -2
> 8ff6a6c06a90a362 (HEAD -> perf/core) perf tools: Fix version kernel tag
> 4e666cdb06eede20 perf tools: Fix dependency for version file creation
> $
> 
> Anyway, your patch works for some cases, so its an improvement and I'll
> apply it, we can continue from there.

Thanks,

I just noticed the "reset --hard HEAD^" problem and not cherry-pick'ing. 
Let me check this tomorrow.

john