Date: Wed, 26 Aug 2015 09:26:56 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>, adrian.hunter@intel.com,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Vince Weaver <vince@deater.net>,
        Arnaldo Carvalho de Melo <acme@infradead.org>,
        linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH v2 0/6] perf: Introduce extended syscall error reporting
Message-ID: <20150826072656.GA19305@gmail.com>
References: <1440492739.2192.7.camel@sipsolutions.net>
 <20150825090252.GB22414@gmail.com>
 <20150825091740.GA23488@gmail.com>
 <1440495246.2192.13.camel@sipsolutions.net>
 <20150825100728.GA1820@gmail.com>
 <1440497981.2192.39.camel@sipsolutions.net>
 <20150826044948.GC14584@gmail.com>
 <CA+55aFw--OFczoY=v17+e2-Q3O0GXnMKRuwzpYpB2qKBpZo=fw@mail.gmail.com>
 <1440572775.1932.1.camel@sipsolutions.net>
 <20150826072020.GA19081@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20150826072020.GA19081@gmail.com>
User-Agent: Mutt/1.5.23 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 929
Lines: 27


* Ingo Molnar <mingo@kernel.org> wrote:

> ... but back then I didn't feel like complicating an error recovery ABI for the 
> needs of the 1%, robust error handling is all about simplicity: if it's not 
> simple, tools won't use it.

And note that it needs to be 'simple' in two places for usage to grow naturally: 

  - the usage site in the kernel
  - the tooling side that recovers the information.

That's why I think that such a form:

	return err_str(-EINVAL, "x86/perf: CPU does not support precise sampling");

is obviously simple on the kernel side as it returns -EINVAL, and is very simple 
on the tooling side as well, if we are allowed to extend prctl().

Thanks,

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/