Re: Floating point exception by perf record

[Hitoshi Mitake]

On 04/06/10 03:31, Arnaldo Carvalho de Melo wrote:
> Em Sun, Apr 04, 2010 at 05:10:57PM +0900, Hitoshi Mitake escreveu:
>> I suffered a mysterious floating point exception when executing perf
>> on current tip/master.
>>
>> For example,
>>
>> % sudo ./perf lock record ./perf bench sched messaging
>> # Running sched/messaging benchmark...
>> # 20 sender and receiver processes per group
>> # 10 groups == 400 processes run
>>
>>       Total time: 1.375 [sec]
>> [ perf record: Woken up 0 times to write data ]
>> [ perf record: Captured and wrote 160.002 MB perf.data (~6990599 
samples) ]
>> [1]    26348 floating point exception  sudo ./perf lock record ./perf
>> bench sched messaging
>>
>> dmesg says that
>>
>> [10212.752490] perf[26348] trap divide error ip:7fade8564310
>> sp:7fff46d926e8 error:0 in libnewt.so.0.52.2[7fade8556000+15000]
>>
>> Example is of perf lock, but this is not a special phenomenon of 
perf lock,
>> other users of perf record, like perf sched, caused the same problem.
>>
>> I found that this might be caused by the line 283 of perf.c
>>
>> 	if (fclose(stdout)) #<- closing stdout!
>> 		die("close failed on standard output: %s", strerror(errno));
>>
>> I don't know well about libnewt, do you know something like cause?
>>
>> The version of libnewt I'm using is 0.52.2 (default of Debian lenny)
>
> I just built a kernel where 'perf lock' can work, but I'm seeing a
> different problem:
>
> [root@doppio ~]# perf lock trace | head -3
>    Warning: Error: expected 'data' but read 'overwrite'
>           swapper-0     [000]   619.086424: lock_acquire: 
0xffff8800029d4b28&q->lock
>           swapper-0     [000]   619.086429: lock_acquire: 
0xffff8800029d08f8&ctx->lock
>           swapper-0     [000]   619.086439: lock_acquire: 
0xffffffff81a38e58 clockevents_lock
> [root@doppio ~]# perf lock report | head -3
>    Warning: Error: expected 'data' but read 'overwrite'
>                  ID                 Name   acquired  contended total 
wait (ns)   max wait (ns)   min wait (ns)
>
> 0xffff8800029d4b28&q->lock          0          0               0 
          0               0
> [root@doppio ~]#
>
> My system details:
>
> [root@doppio ~]# uname -a
> Linux doppio.ghostprotocols.net 2.6.34-rc3-tip+ #1 SMP Mon Apr 5 
13:49:42 BRT 2010 x86_64 x86_64 x86_64 GNU/Linux
> [root@doppio ~]# rpm -q newt
> newt-0.52.10-4.fc11.x86_64
> [root@doppio ~]#
>
> No segfaults here :-\
>
> - Arnaldo
>

I tested perf lock trace and got a similar error (but different).
% sudo ./perf lock trace
  Fatal: reading input file (size expected=3 received=0)
It seems that perf.data is broken :( I'll search the cause.

   Hitoshi
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