From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Berg Subject: Re: [PATCH RFC v3 1/6] exterr: Introduce extended syscall error reporting Date: Tue, 15 Sep 2015 19:02:19 +0200 Message-ID: <1442336539.1914.34.camel@sipsolutions.net> References: <1441987205-4021-1-git-send-email-alexander.shishkin@linux.intel.com> <1441987205-4021-2-git-send-email-alexander.shishkin@linux.intel.com> <20150914141931.39f6be92@lwn.net> <87a8snn4zz.fsf@ashishki-desk.ger.corp.intel.com> <1442327514.1914.31.camel@sipsolutions.net> <877fnrn1sj.fsf@ashishki-desk.ger.corp.intel.com> <20150915103556.36b06f09@lwn.net> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150915103556.36b06f09-T1hC0tSOHrs@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jonathan Corbet , Alexander Shishkin Cc: Peter Zijlstra , Ingo Molnar , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, vince-yfjdyHUqu3OsTnJN9+BGXg@public.gmane.org, eranian-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, Arnaldo Carvalho de Melo , linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-api@vger.kernel.org > I think that anything other than the errno "grab it now or lose it" > behavior will prove confusing. I don't think there is any other way to > know that a given error report corresponds to a specific system call. > Library calls can mess it up. Kernel changes adding extended reporting to > new system calls can mess it up. Applications cannot possibly be expected > to know which system calls might change the error-reporting status, they > *have* to assume all of them will. > Yeah I was about to say something similar - an application that expects a certain syscall to have extended errors will get confused if running on an older kernel where that syscall in fact does *not* have extended errors (and thus also doesn't clear extended errors) and therefore the extended error from a previous syscall could still be lingering on (for example because the application didn't care to fetch it for that previo us syscall.) johannes