From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org ([103.22.144.67]:33479 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750808AbeA2ENq (ORCPT ); Sun, 28 Jan 2018 23:13:46 -0500 In-Reply-To: <1470102616-18346-1-git-send-email-stewart@linux.vnet.ibm.com> To: Stewart Smith , linuxppc-dev@lists.ozlabs.org From: Michael Ellerman Cc: neelegup@linux.vnet.ibm.com, Stewart Smith , stable@vger.kernel.org Subject: Re: rtc-opal: Fix handling of firmware error codes, prevent busy loops Message-Id: <3zVGN90phWz9s83@ozlabs.org> Date: Mon, 29 Jan 2018 15:13:44 +1100 (AEDT) Sender: stable-owner@vger.kernel.org List-ID: On Tue, 2016-08-02 at 01:50:16 UTC, Stewart Smith wrote: > According to the OPAL docs: > https://github.com/open-power/skiboot/blob/skiboot-5.2.5/doc/opal-api/opal-rtc-read-3.txt > https://github.com/open-power/skiboot/blob/skiboot-5.2.5/doc/opal-api/opal-rtc-write-4.txt > OPAL_HARDWARE may be returned from OPAL_RTC_READ or OPAL_RTC_WRITE and this > indicates either a transient or permanent error. > > Prior to this patch, Linux was not dealing with OPAL_HARDWARE being a > permanent error particularly well, in that you could end up in a busy > loop. > > This was not too hard to trigger on an AMI BMC based OpenPOWER machine > doing a continuous "ipmitool mc reset cold" to the BMC, the result of > that being that we'd get stuck in an infinite loop in opal_get_rtc_time. > > We now retry a few times before returning the error higher up the stack. > > Cc: stable@vger.kernel.org > Signed-off-by: Stewart Smith Applied to powerpc next, thanks. https://git.kernel.org/powerpc/c/5b8b58063029f02da573120ef4dc90 cheers