Date:	Thu, 19 Nov 2015 19:50:37 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Jiri Olsa <jolsa@...nel.org>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: perf BPF/elfdep intermitent build problems



On 2015/11/19 6:44, Arnaldo Carvalho de Melo wrote:
> Have you guys ever saw this?
>
> [acme@zoo linux]$ alias m
> alias m='perf stat -e cycles make O=/tmp/build/perf -C tools/perf
> install-bin'
> [acme @zoo linux]$ m
> make: Entering directory '/home/git/linux/tools/perf'
>    BUILD:   Doing 'make -j4' parallel build
> make[2]: Nothing to be done for 'fixdep'.
>    CC       /tmp/build/perf/util/machine.o
>    LD       /tmp/build/perf/util/libperf-in.o

At the head of 'make' output I don't see

Auto-detecting system features:
...

So I guess your /tmp/build/perf is not an empty directory? Therefore
there might be some garbage in that directory. At least a FEATURE-DUMP
should be there, and that file should match perf's second pass feature
check, and in perf's checks libelf and libpf are both passed, or libbpf
won't be built.

> No libelf found
> BPF API too old

But when building libbpf, these two feature checks failed. Also, the
result is same to the garbage left in /tmp/build/perf/FEATURE-DUMP.libbpf,
or feature check result matrix should be output.

So there are something blocks lib/bpf's feature checks but not
affect perf itselves feature checks.

> Makefile:191: recipe for target 'elfdep' failed
> make[2]: *** [elfdep] Error 255
> make[2]: *** Waiting for unfinished jobs....
> Makefile:194: recipe for target 'bpfdep' failed
> make[2]: *** [bpfdep] Error 255
> Makefile.perf:434: recipe for target '/tmp/build/perf/libbpf.a' failed
> make[1]: *** [/tmp/build/perf/libbpf.a] Error 2
> make[1]: *** Waiting for unfinished jobs....
>    LD       /tmp/build/perf/libperf-in.o
> Makefile:87: recipe for target 'install-bin' failed
> make: *** [install-bin] Error 2
> make: Leaving directory '/home/git/linux/tools/perf'
>
>   Performance counter stats for 'make O=/tmp/build/perf -C tools/perf
> install-bin':
>
>      10,265,920,369      cycles
>
>         3.002799545 seconds time elapsed
>
> [acme@zoo linux]$
>
>
> If I go and try doing a clean on the libbpf dir I see another problem:
>
> [acme@zoo linux]$ cd tools/lib/bpf
> [acme@zoo bpf]$ make clean
>
> Auto-detecting system features:
> ...                        libelf: [ OFF ]
> ...                           bpf: [ OFF ]
>
>    CLEAN    libbpf
>    CLEAN    core-gen
> [acme@zoo bpf]$

Could you please provid the content of following files:

/tmp/build/perf/feature/test-libelf*make.output
/tmp/build/perf/feature/test-bpf.make.output

and those outputs in your perf source tree after you
do this 'perf clean'? If feature check fail these files should
tell us the reason.

> No need for feature detection when doing a plain 'make clean', right?

Please have a look at my patch "tools lib bpf: Don't feature check
when cleaning".

> But then, after cleaning it again, and entering tools/perf to do a 'make
> clean' as well, it does the feature detection at a second 'make clean'
> and this time it shoes [ on ] for both libelf and bpf, and this time
> I manage to build perf.

So the one blocks libbpf's feature checking is removed.
It inside perf source directory, but affects build dir...

Still no clue.

Jiri, can you find something?

Thank you.


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