linux-kernel - Re: [PATCH v5 06/21] perf arm-spe: Refactor printing string to buffer

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Date:   Thu, 29 Oct 2020 18:51:59 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     André Przywara <andre.przywara@....com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Dave Martin <Dave.Martin@....com>,
        Wei Li <liwei391@...wei.com>,
        James Clark <james.clark@....com>, Al Grant <Al.Grant@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 06/21] perf arm-spe: Refactor printing string to buffer

Hi Andre,

On Thu, Oct 29, 2020 at 10:23:39AM +0000, André Przywara wrote:

[...]

> > +static int arm_spe_pkt_snprintf(int *err, char **buf_p, size_t *blen,
> > +				const char *fmt, ...)
> > +{
> > +	va_list ap;
> > +	int ret;
> > +
> > +	va_start(ap, fmt);
> > +	ret = vsnprintf(*buf_p, *blen, fmt, ap);
> > +	va_end(ap);
> > +
> > +	if (ret < 0) {
> > +		if (err && !*err)
> > +			*err = ret;
> > +	} else {
> > +		*buf_p += ret;
> > +		*blen -= ret;
> > +	}
> > +
> > +	return ret;
> > +}
> 
> So this now implements the old behaviour of ignoring previous errors, in
> all cases, since we don't check for errors and bail out in the callers.
> 
> If you simply check for validity of err and for it being 0 before
> proceeding with the va_start() above, this should be fixed.

I think you are suggesting below code, could you take a look for it
before I proceed to respin new patch?

static int arm_spe_pkt_snprintf(int *err, char **buf_p, size_t *blen,
				const char *fmt, ...)
{
	va_list ap;
	int ret;

        /* Bail out if any error occurred */
        if (err && *err)
                return *err;

	va_start(ap, fmt);
	ret = vsnprintf(*buf_p, *blen, fmt, ap);
	va_end(ap);

	if (ret < 0) {
		if (err && !*err)
			*err = ret;
	} else {
		*buf_p += ret;
		*blen -= ret;
	}

	return ret;
}

Thanks,
Leo