Hi.

I hit this perf build error with next-20160208 with GCC 4.6.

  CC       tests/bp_signal.o
tests/bp_signal.c: In function ‘__event’:
tests/bp_signal.c:106:47: error: declaration of ‘signal’ shadows a
global declaration [-Werror=shadow]
tests/bp_signal.c: In function ‘bp_event’:
tests/bp_signal.c:144:37: error: declaration of ‘signal’ shadows a
global declaration [-Werror=shadow]
tests/bp_signal.c: In function ‘wp_event’:
tests/bp_signal.c:149:37: error: declaration of ‘signal’ shadows a
global declaration [-Werror=shadow]

The build error is introduced with "perf test: Check environment
before start real BPF test".

commit 6a7d550e8b2eeb380ab85d9bc53571123b98345b
Author: Wang Nan [off-list ref]
Date:   Mon Jan 25 09:55:53 2016 +0000

    perf test: Check environment before start real BPF test

    Copying perf to old kernel system results:

      # perf test bpf
      37: Test BPF filter                                          :
      37.1: Test basic BPF filtering                               : FAILED!
      37.2: Test BPF prologue generation                           : Skip

    However, in case when kernel doesn't support a test case it should
    return 'Skip', 'FAILED!' should be reserved for kernel tests for when
    the kernel supports a feature that then fails to work as advertised.

    This patch checks environment before real testcase.

    Signed-off-by: Wang Nan [off-list ref]
    Suggested-by: Arnaldo Carvalho de Melo [off-list ref]
    Cc: Alexei Starovoitov [off-list ref]
    Cc: Brendan Gregg [off-list ref]
    Cc: Daniel Borkmann [off-list ref]
    Cc: He Kuang [off-list ref]
    Cc: Jiri Olsa [off-list ref]
    Cc: Li Zefan [off-list ref]
    Cc: Masami Hiramatsu [off-list ref]
    Cc: Namhyung Kim [off-list ref]
    Cc: Peter Zijlstra [off-list ref]
    Cc: Will Deacon [off-list ref]
    Cc: pi3orama@163.com
    Link: http://lkml.kernel.org/r/1453715801-7732-7-git-send-email-wangnan0@huawei.com
    Signed-off-by: Arnaldo Carvalho de Melo [off-list ref]

Cheers,
Vinson