Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753372AbaDXVBe (ORCPT ); Thu, 24 Apr 2014 17:01:34 -0400 Received: from mail-ig0-f172.google.com ([209.85.213.172]:45258 "EHLO mail-ig0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752556AbaDXVBX convert rfc822-to-8bit (ORCPT ); Thu, 24 Apr 2014 17:01:23 -0400 MIME-Version: 1.0 In-Reply-To: <5358BDDF.1010709@ti.com> References: <1397040727-2447-1-git-send-email-peter.ujfalusi@ti.com> <5358BDDF.1010709@ti.com> From: Grant Likely Date: Thu, 24 Apr 2014 22:01:02 +0100 X-Google-Sender-Auth: 2udtDmCpTpCfO7vC6rlFGyK8R8U Message-ID: Subject: Re: [PATCH v2 0/2] drivercore: deferral race condition fix To: Peter Ujfalusi Cc: Greg Kroah-Hartman , Mark Brown , Liam Girdwood , Linux Kernel Mailing List Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 24, 2014 at 8:31 AM, Peter Ujfalusi wrote: > Hi Greg, Grant, > > On 04/09/2014 01:52 PM, Peter Ujfalusi wrote: >> Hi, >> >> Changes since v1: >> - The deferral race detection and handling has been moved to >> driver_deferred_probe_trigger() and driver_deferred_probe_add() functions with >> comment section. >> - driver_deferred_probe_add/del function needed to be moved. Both of them placed >> after driver_deferred_probe_trigger() so they remain together. >> - I have not added the Acked-by from Mark and Grant since the patch itself >> changed from v1, but the functionality remained. > > Is this solution sounds good? Do you want me to resend the two patch? You don't need to resend. I just got back from vacation. I will look at it tomorrow. g. > > Regards, > P?ter > >> Explanantion of the issue (from patch 2): >> When the kernel is built with CONFIG_PREEMPT it is possible to reach a state >> when all modules loaded but some driver still stuck in the deferred list >> and there is a need for external event to kick the deferred queue to probe >> these drivers. >> >> The issue has been observed on embedded systems with CONFIG_PREEMPT enabled, >> audio support built as modules and using nfsroot for root filesystem. >> >> The following log fragment shows such sequence when all audio modules >> were loaded but the sound card is not present since the machine driver has >> failed to probe due to missing dependency during it's probe. >> The board is am335x-evmsk (McASP<->tlv320aic3106 codec) with davinci-evm >> machine driver: >> >> ... >> [ 12.615118] davinci-mcasp 4803c000.mcasp: davinci_mcasp_probe: ENTER >> [ 12.719969] davinci_evm sound.3: davinci_evm_probe: ENTER >> [ 12.725753] davinci_evm sound.3: davinci_evm_probe: snd_soc_register_card >> [ 12.753846] davinci-mcasp 4803c000.mcasp: davinci_mcasp_probe: snd_soc_register_component >> [ 12.922051] davinci-mcasp 4803c000.mcasp: davinci_mcasp_probe: snd_soc_register_component DONE >> [ 12.950839] davinci_evm sound.3: ASoC: platform (null) not registered >> [ 12.957898] davinci_evm sound.3: davinci_evm_probe: snd_soc_register_card DONE (-517) >> [ 13.099026] davinci-mcasp 4803c000.mcasp: Kicking the deferred list >> [ 13.177838] davinci-mcasp 4803c000.mcasp: really_probe: probe_count = 2 >> [ 13.194130] davinci_evm sound.3: snd_soc_register_card failed (-517) >> [ 13.346755] davinci_mcasp_driver_init: LEAVE >> [ 13.377446] platform sound.3: Driver davinci_evm requests probe deferral >> [ 13.592527] platform sound.3: really_probe: probe_count = 0 >> >> In the log the machine driver enters it's probe at 12.719969 (this point it >> has been removed from the deferred lists). McASP driver already executing >> it's probing (since 12.615118). >> The machine driver tries to construct the sound card (12.950839) but did >> not found one of the components so it fails. After this McASP driver >> registers all the ASoC components (the machine driver still in it's probe >> function after it failed to construct the card) and the deferred work is >> prepared at 13.099026 (note that this time the machine driver is not in the >> lists so it is not going to be handled when the work is executing). >> Lastly the machine driver exit from it's probe and the core places it to >> the deferred list but there will be no other driver going to load and the >> deferred queue is not going to be kicked again - till we have external event >> like connecting USB stick, etc. >> >> The proposed solution is to try the deferred queue once more when the last >> driver is asking for deferring and we had drivers loaded while this last >> driver was probing. >> >> This way we can avoid drivers stuck in the deferred queue. >> >> Regards, >> Peter >> --- >> Peter Ujfalusi (2): >> drivercore: dd: Move driver_deferred_probe_add/del function down in >> the code >> drivercore: deferral race condition fix >> >> drivers/base/dd.c | 71 +++++++++++++++++++++++++++++++++++++------------------ >> 1 file changed, 48 insertions(+), 23 deletions(-) > -- 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/