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Date: Tue, 4 Jan 2011 12:12:14 -0200
From: Arnaldo Carvalho de Melo <acme@infradead.org>
To: Stephane Eranian <eranian@google.com>
Cc: linux-kernel@vger.kernel.org, Frederic Weisbecker <fweisbec@gmail.com>,
        Han Pingtian <phan@redhat.com>, Mike Galbraith <efault@gmx.de>,
        Paul Mackerras <paulus@samba.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Tom Zanussi <tzanussi@gmail.com>, Thomas Gleixner <tglx@linutronix.de>,
        mingo@elte.hu
Subject: Re: [GIT PULL||RFC 00/11] perf library and regression testing
 improvements
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Em Tue, Jan 04, 2011 at 02:59:00PM +0100, Stephane Eranian escreveu:
> Arnaldo,
> 
> The version of perf at tip-x86 commit 9274b36, segfaults for me:
> 
> $ gdb perf
> (gdb) r stat date
> 
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 0x7fdc602eb6e0 (LWP 4590)]
> cmd_stat (argc=1, argv=0x7fff6fa2a9f0, prefix=<value optimized out>)
> at builtin-stat.c:206
> 206			update_stats(&ps->res_stats[i], count[i]);
> (gdb) bt
> #0  cmd_stat (argc=1, argv=0x7fff6fa2a9f0, prefix=<value optimized
> out>) at builtin-stat.c:206
> #1  0x0000000000405c8b in handle_internal_command (argc=2,
> argv=0x7fff6fa2a9f0) at perf.c:286
> #2  0x00000000004060b0 in main (argc=2, argv=0x7fff6fa2a680) at perf.c:403
> 
> Most like ps is NULL.

Well, it shoudldn't, as we do, before calling that function:

        list_for_each_entry(pos, &evsel_list, node) {
                if (perf_evsel__alloc_stat_priv(pos) < 0 ||
                    perf_evsel__alloc_counts(pos, cpus->nr) < 0 ||
                    perf_evsel__alloc_fd(pos, cpus->nr, threads->nr) < 0)
                        goto out_free_fd;
        }

And then at line 206 it does:

	update_stats(&ps->res_stats[i], count[i]);

ps was set to be:

	struct perf_stat *ps = counter->priv;

that was set by perf_evsel__alloc_stat_priv

and count is

u64 *count = counter->counts->aggr.values;

That was allocated by perf_evsel__alloc_counts

/me scratches head :-\

- Arnaldo