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

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Date:	Wed, 19 Oct 2011 17:20:11 -0200
From:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
To:	David Ahern <dsahern@...il.com>
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

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?

- Arnaldo
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