linux-kernel - Re: Floating point exception by perf record

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Message-ID: <4BBD7BB1.1070105@dcl.info.waseda.ac.jp>
Date:	Thu, 08 Apr 2010 15:46:09 +0900
From:	Hitoshi Mitake <mitake@....info.waseda.ac.jp>
To:	Arnaldo Carvalho de Melo <acme@...radead.org>
CC:	Ingo Molnar <mingo@...e.hu>, Paul Mackerras <paulus@...ba.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Floating point exception by perf record

On 04/07/10 19:38, Arnaldo Carvalho de Melo wrote:
 > Em Wed, Apr 07, 2010 at 05:32:24PM +0900, Hitoshi Mitake escreveu:
 >> On 04/06/10 03:31, Arnaldo Carvalho de Melo wrote:
 >>> Em Sun, Apr 04, 2010 at 05:10:57PM +0900, Hitoshi Mitake escreveu:
 >>> [root@...pio ~]# 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@...pio ~]#
 >>>
 >>> My system details:
 >>>
 >>> [root@...pio ~]# 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@...pio ~]# rpm -q newt
 >>> newt-0.52.10-4.fc11.x86_64
 >>> [root@...pio ~]#
 >>>
 >>> 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.
 >
 > Take a look at:
 >
 > http://git.kernel.org/?p=linux/kernel/git/acme/linux-2.6.git;a=summary
 >
 > "perf" branch, there is at least one fix there, the "overwrite" one.
 >

Thanks for your notify!
I applied changes on your branch, but my problem was not solved...

I found that the member "offset" of struct perf_file_header is broken.
I made this easy change,

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 6c9aa16..dbea087 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -571,6 +571,7 @@ int perf_header__process_sections(struct perf_header 
*self, int fd,
         if (perf_header__getbuffer64(self, fd, feat_sec, sec_size))
                 goto out_free;

+       printf("feat_sec->offset:%llu\n", feat_sec->offset);
         err = 0;
         while (idx < nr_sections && feat < HEADER_LAST_FEATURE) {
                 if (perf_header__has_feat(self, feat)) {

And the result is this:

% sudo ./perf lock report
   Fatal: reading input file (size expected=3 received=0)
feat_sec->offset:18014402804449281 # <- Wow! :(

It seems that header of perf.data is broken...
But it may be a cause of this problem, I'll try to fix it.

Thanks,
    Hitoshi

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