linux-kernel - Re: [PATCH 02/10] perf, tools: Support handling complete branch stacks as histograms

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Message-ID: <20141113195208.GS12538@two.firstfloor.org>
Date:	Thu, 13 Nov 2014 20:52:08 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Andi Kleen <andi@...stfloor.org>, jolsa@...hat.com,
	linux-kernel@...r.kernel.org, namhyung@...nel.org,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 02/10] perf, tools: Support handling complete branch
 stacks as histograms

On Thu, Nov 13, 2014 at 04:14:17PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Wed, Nov 12, 2014 at 06:05:20PM -0800, Andi Kleen escreveu:
> > +static int remove_loops(struct branch_entry *l, int nr)
> > +{
> > +	int i, j, off;
> > +	unsigned char chash[CHASHSZ];
> > +
> > +	memset(chash, NO_ENTRY, sizeof(chash));
> > +
> > +	BUG_ON(nr >= 256);
> 
> What is wrong with return -1 and propagating the error, so that the user
> is informed if the data being processed is bogus, stop processing with a
> warning or continue processing if finding the next valid record is
> possible?

The error doesn't depend on the record. There is a check for the record
being < 127 in front of this. This is merely to catch that 
if someone increases PERF_MAX_BRANCH_DEPTH to below 255 they need
to increase the type of the hash table from u8.


-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.
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