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

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Message-ID: <20160512072542.GM3192@twins.programming.kicks-ass.net>
Date:	Thu, 12 May 2016 09:25:42 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
Cc:	linux-perf-users@...r.kernel.org,
	Vince Weaver <vincent.weaver@...ne.edu>,
	linux-kernel@...r.kernel.org, acme@...hat.com,
	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 Thu, May 12, 2016 at 12:24:25PM +0530, Vineet Gupta wrote:
> On Thursday 12 May 2016 12:12 PM, Peter Zijlstra wrote:
> >> 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)
> > Durr, so what does userspace see?
> 
> It sees the "value" of ENOTSUPP, i.e. 524 but there is no symbolic reference to it :-)

Ah.. which might be a hint that nobody is actually explicitly testing
for this and we might just get away with changing the ABI.

Vince, what say you; shall we try and get away with it? ;-)