Re: [PATCH 3/3 v2] perf tool: give user better message if preciseis not supported

From: David Ahern
Date: Fri Sep 14 2012 - 07:43:42 EST

On 9/14/12 5:36 AM, Ingo Molnar wrote:
Well, then that is useful information we *lost*, and that
situation needs to be improved on the ABI side: an expanded
error code present in the event structure, copied back to
user-space on errors, or so.

(Alternatively, a special event channel just to pass back
expanded error conditions.)

Computers are supposed to make life easier for humans, by
answering such "what did go wrong?" questions. Our losing of
precise error conditions is a usability bug really - and in the
perf project we are in a unique position to be able to improve
both the kernel side code and make immediate use of it on the
tooling side as well.

Understood and there have been suggestions on how to definitely state what the kernel side did not like. I like Peter's last suggestion -- something along the lines of clearing attr on a failure except the offending setting.

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