linux-kernel - Re: [RFC 2/2] perf/core: change errno for sampling event not supported in hardware

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Message-ID: <5734229B.90706@synopsys.com>
Date:	Thu, 12 May 2016 11:58:43 +0530
From:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	<acme@...hat.com>, Vince Weaver <vincent.weaver@...ne.edu>,
	<linux-kernel@...r.kernel.org>, <linux-perf-users@...r.kernel.org>,
	<linux-snps-arc@...ts.infradead.org>, <mingo@...nel.org>
Subject: Re: [RFC 2/2] perf/core: change errno for sampling event not
 supported in hardware

On Thursday 12 May 2016 01:06 AM, Peter Zijlstra wrote:
> On Mon, May 09, 2016 at 10:53:43PM +0530, Vineet Gupta wrote:
> 
>> > Right thats what I feared. But hold on, I don't think we need to change the ABI to
>> > achieve what we want. Gosh why did I even take that path.
>> > 
>> > Currently the errno switch case in perf_evsel__open_strerror() in doesn't handle
>> > ENOTSUPP. So how about we add that - augmented with the same sample_period !0
>> > check to barf for lack of sampling support.
>> > 
>> > Do you see anything wrong with that ?
>
> Should work I think.

Tried that and doesn't even compile. Reconfirms what Vince said, ENOTSUPP is not
exposed to userspace (being in include/linux and not include/uapi/linux)