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

From	Vince Weaver <vincent.weaver@maine.edu>
Newsgroups	linux.kernel
Subject	Re: [RFC 2/2] perf/core: change errno for sampling event not supported in hardware
Date	2016-05-09 16:00 +0200
Message-ID	<rwTT3-6II-1@gated-at.bofh.it> (permalink)
References	<rwPPr-2FZ-5@gated-at.bofh.it> <rwPPt-2FZ-35@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On Mon, 9 May 2016, Vineet Gupta wrote:

> This allows userspace to identify this case specifically from the
> catch all error msg it prints currently.
> 
> This is an ABI change

An ABI change which will probably break things.

The original change from ENODEV to ENOTSUPP managed to break things 
although it took four kernel releases before anyone noticed.

The usage of ENOTSUPP was my fault, though I feel like at the time I was 
told that ENOTSUPP is for internal kernel usage and would be converted to 
EOPNOTSUPP when returning an error to userspace.  But now I 
can't find any sort of reference for that at all, except the fact that

	/usr/include/x86_64-linux-gnu/bits/errno.h

has
	/* Linux has no ENOTSUP error code.  */
	# define ENOTSUP EOPNOTSUPP

in it... but wait, that's ENOTSUP not ENOTSUPP.  Blargh.

Vince

Thread

[RFC 0/2] report perf sampling failing due to PMU lacking overflow intr support Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-05-09 11:40 +0200
  [RFC 2/2] perf/core: change errno for sampling event not supported in hardware Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-05-09 11:40 +0200
    Re: [RFC 2/2] perf/core: change errno for sampling event not supported  in hardware Vince Weaver <vincent.weaver@maine.edu> - 2016-05-09 16:00 +0200
      Re: [RFC 2/2] perf/core: change errno for sampling event not  supported in hardware Vineet Gupta <vgupta@synopsys.com> - 2016-05-09 19:30 +0200
        Re: [RFC 2/2] perf/core: change errno for sampling event not supported  in hardware Vince Weaver <vincent.weaver@maine.edu> - 2016-05-11 05:40 +0200
        Re: [RFC 2/2] perf/core: change errno for sampling event not  supported in hardware Peter Zijlstra <peterz@infradead.org> - 2016-05-11 21:40 +0200
          Re: [RFC 2/2] perf/core: change errno for sampling event not  supported in hardware Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-05-12 08:30 +0200
            Re: [RFC 2/2] perf/core: change errno for sampling event not  supported in hardware Peter Zijlstra <peterz@infradead.org> - 2016-05-12 08:50 +0200
              Re: [RFC 2/2] perf/core: change errno for sampling event not  supported in hardware Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-05-12 09:00 +0200
                Re: [RFC 2/2] perf/core: change errno for sampling event not  supported in hardware Peter Zijlstra <peterz@infradead.org> - 2016-05-12 09:30 +0200

csiph-web