linux-kernel - Re: [PATCH RFC v3 1/6] exterr: Introduce extended syscall error reporting

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Message-ID: <877fnrn1sj.fsf@ashishki-desk.ger.corp.intel.com>
Date:	Tue, 15 Sep 2015 18:24:28 +0300
From:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:	Johannes Berg <johannes@...solutions.net>,
	Jonathan Corbet <corbet@....net>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	vince@...ter.net, eranian@...gle.com,
	Arnaldo Carvalho de Melo <acme@...radead.org>
Subject: Re: [PATCH RFC v3 1/6] exterr: Introduce extended syscall error reporting

Johannes Berg <johannes@...solutions.net> writes:

> On Tue, 2015-09-15 at 17:15 +0300, Alexander Shishkin wrote:
>> 
>> > It seems to me that current->ext_err_code needs to be cleared on 
>> > each system call entry (except for your special prctl() of 
>> > course!).
>> 
>> I'd say, it should be up to the program to decide for how long they 
>> want to keep the extended error code around.
>> 
>
> I'm not convinced that works - imagine a library wanting to use the
> prctl(), but the main application isn't doing that. Should the library
> clear it before every call, to be sure it's not getting stale data?
> etc.

In other words, a syscall that's capable of throwing an extended error
does clear the current::ext_err_code every time, but not other
syscalls. Otherwise it will indeed get very confusing.

Regards,
--
Alex
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