linux-kernel - Re: [PATCH] Add inverted call graph report support to perf tool

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Message-ID: <20110312013125.GA24618@dev1756.snc6.facebook.com>
Date:	Fri, 11 Mar 2011 17:31:25 -0800
From:	Arun Sharma <asharma@...com>
To:	Sam Liao <phyomh@...il.com>
Cc:	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	acme@...hat.com
Subject: Re: [PATCH] Add inverted call graph report support to perf tool

On Mon, Mar 07, 2011 at 09:43:27PM +0800, Sam Liao wrote:
> +
> +	/* reverse call chain data */
> +	if (reverse_call && symbol_conf.use_callchain && sample->callchain) {

You probably want to check for nr > 1 here, as in:

 	/* reverse call chain data */
-	if (reverse_call && symbol_conf.use_callchain && sample->callchain) {
+	if (reverse_call && symbol_conf.use_callchain && sample->callchain
+	    && (sample->callchain->nr > 1)) {
 		struct ip_callchain *chain;
 		int i, j;
 		u64 tmp_ip;

Otherwise, if you get a callchain with ->nr == 0, the loop with (nr - 2) will
go on for a long time.

 -Arun
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