On 2014/10/22 15:00, Namhyung Kim wrote:
> On Thu, 16 Oct 2014 11:08:29 +0800, Wang Nan wrote:
>> When 'perf record' write headers, it calls write_xxx in
>> tools/perf/util/header.c, and check return value. It rolls back all
>> working only when return value is negative.
>>
>> This patch ensures write_cpudesc() and write_total_mem() return negative
>> number
>> when error. Without this patch, headers reported by 'perf report' header is
>> error in some platform. Following output is caputured on ARM, which doesn't
>> contain "Processor" field in /proc/cpuinfo. See "cpudesc", "total memory" and
>> "cmdline" field.
>>
>> bash-4.2# perf record ls
>> ...
>> [ perf record: Woken up 1 times to write data ]
>> [ perf record: Captured and wrote 0.001 MB perf.data (~36 samples) ]
>> bash-4.2# perf report --stdio --header
>> Error:
>> The perf.data file has no samples!
>> # ========
>> # captured on: Fri Sep 12 10:09:10 2014
>> # hostname : arma15el
>> # os release : 3.17.0+
>> # perf version : 3.10.53
>> # arch : armv7l
>> # nrcpus online : 4
>> # nrcpus avail : 1
>> # cpudesc : (null)
>> # total memory : 0 kB
>> # cmdline :
>> # event : name = cycles, type = 0, config = 0x0, config1 = 0x0, config2 =
>> 0x0, excl_usr = 0, excl_kern = 0, excl_host = 0, excl_guest = 1, precise_ip
>> = 0
>> # pmu mappings: not available
>> # ========
>> #
>>
>> Signed-off-by: Wang Nan <wangn...@huawei.com>
>
> I guess the total_memory, cmdline and pmu mappings are somehow affected
> by the broken cpudesc. Do they have their own problem on ARM?
>
The buggy output is caused by cpudesc's problem. I didn't trigger their own
problem on ARM because
'total memory' and cmdline are always success. I find the error in
write_total_mem() by checking
code by hand.
Thanks.
> Anyway I think it's good to check the result properly, so
>
> Acked-by: Namhyung Kim <namhy...@kernel.org>
>
> Thanks,
> Namhyung
>
>
>> ---
>> tools/perf/util/header.c | 7 +++++--
>> 1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
>> index ce0de00..39b80ac 100644
>> --- a/tools/perf/util/header.c
>> +++ b/tools/perf/util/header.c
>> @@ -605,8 +605,10 @@ static int write_cpudesc(int fd, struct perf_header *h
>> __maybe_unused,
>> break;
>> }
>>
>> - if (ret)
>> + if (ret) {
>> + ret = -1;
>> goto done;
>> + }
>>
>> s = buf;
>>
>> @@ -950,7 +952,8 @@ static int write_total_mem(int fd, struct perf_header *h
>> __maybe_unused,
>> n = sscanf(buf, "%*s %"PRIu64, &mem);
>> if (n == 1)
>> ret = do_write(fd, &mem, sizeof(mem));
>> - }
>> + } else
>> + ret = -1;
>> free(buf);
>> fclose(fp);
>> return ret;
--
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