linux-kernel - Re: [PATCH] perf top: fix crash on annotate request

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Date:	Wed, 19 Oct 2011 14:21:06 -0600
From:	David Ahern <dsahern@...il.com>
To:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
CC:	linux-kernel@...r.kernel.org, mingo@...e.hu, peterz@...radead.org,
	fweisbec@...il.com
Subject: Re: [PATCH] perf top: fix crash on annotate request



On 10/19/2011 01:20 PM, Arnaldo Carvalho de Melo wrote:
> Em Wed, Oct 19, 2011 at 12:44:48PM -0600, David Ahern escreveu:
>> On 10/19/2011 12:38 PM, Arnaldo Carvalho de Melo wrote:
>>> Em Wed, Oct 19, 2011 at 12:23:18PM -0600, David Ahern escreveu:
>>>> Hitting an annotate case where src is not set and
>>>> perf-top crashes.
> 
>>> How did you got there? 
>>
>> I was starting perf top, selecting a symbol and pressing 'a'. In the
>> crash case it was the perf command itself.
> 
> Humm, looks like a race, the old 'perf top --tui' had this:
> 
> static void perf_top_browser__annotate(struct perf_top_browser *browser)
> {
>         struct sym_entry *syme = browser->selection;
>         struct symbol *sym = sym_entry__symbol(syme);
>         struct annotation *notes = symbol__annotation(sym);
>         struct perf_top *top = browser->b.priv;
> 
>         if (notes->src != NULL)
>                 goto do_annotation;
> 
>         pthread_mutex_lock(&notes->lock);
> 
>         top->sym_filter_entry = NULL;
> 
>         if (symbol__alloc_hist(sym, top->evlist->nr_entries) < 0) {
>                 pr_err("Not enough memory for annotating '%s' symbol!\n",
>                        sym->name);
>                 pthread_mutex_unlock(&notes->lock);
>                 return;
>         }
> 
>         top->sym_filter_entry = syme;
> 
>         pthread_mutex_unlock(&notes->lock);
> do_annotation:
>         symbol__tui_annotate(sym, syme->map, 0, top->delay_secs * 1000);
> }
> 
> 
> Which is not even completely right, the notes->src should happen inside
> the lock, like parse_source in the --stdio...
> 
> Can you check if that is the problem? I.e. take notes->lock, check if
> ->src is NULL, if so call symbol__alloc_hist, etc?

Well, I rebooted my laptop during lunch and cannot repeat the crash. I
had installed prelink yesterday to get it to do its thing which it had
-- almost every process (gnome, daemons, terminals, shells, etc) had
deleted dso's.

Today (just a suspend overnight) I started looking at the perf-top code.
I noticed that the annotate key was doing nothing - except on the perf
command itself where it crashed.

After rebooting - which cleared all the prelink deletions - it works
fine. Re-running prelink (force mode) gets the prelink deletions, but
annotate in perf-top works fine. If it happens again I'll try your
suggestion.

David

> 
> - Arnaldo
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