From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5664AC5CFFE for ; Mon, 10 Dec 2018 19:43:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 012FE20672 for ; Mon, 10 Dec 2018 19:43:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=intel-com.20150623.gappssmtp.com header.i=@intel-com.20150623.gappssmtp.com header.b="Zb7DbFyz" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 012FE20672 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729517AbeLJTna (ORCPT ); Mon, 10 Dec 2018 14:43:30 -0500 Received: from mail-oi1-f196.google.com ([209.85.167.196]:32825 "EHLO mail-oi1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727970AbeLJTna (ORCPT ); Mon, 10 Dec 2018 14:43:30 -0500 Received: by mail-oi1-f196.google.com with SMTP id c206so10027283oib.0 for ; Mon, 10 Dec 2018 11:43:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=ZWbXmtNfJh7V5oDcbfdFWxGL8EBeD9YIn39i34tpgQA=; b=Zb7DbFyzhc1cqbKDm6LUfEYkUH4CvpS81D3WaSiO0tRgIRxssqnj/LKQ+mdKhdzY+I jL4PO/Q2QEiWzWWAYS5Ku5vtRDTLSSBov5SKAt7ulb+W9oJIhXABHSsD8Q3+KTbjhdPw Io/0pN3NqHIOGFs23F2mIgDSU9oMfzoMkV0F/TfrL317NKSoNFsNQfKufGvlHTaxC+xA 0Hb09VsesjwlayC4zk1rLe4BI1Rq8pj00GV3pvBk2tUBF+NBIOEugtWu4hxhSJQDv+DT 9U0YZr4hSO8+yRsBhtsLoB48PAUkHMKMcy36n/Q3gNsEXE4yAcvfeGDax/PHLNuk4ui0 xclg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=ZWbXmtNfJh7V5oDcbfdFWxGL8EBeD9YIn39i34tpgQA=; b=j2EZXoW52xlsDY42S7HeMA9TTgpdgkxZrhD5F5HeNJWOBRr6x50sf1zuJi/GPpwfeb PKnSNBKV5B4zgm+xQB2Qlp4Dcwx9LPmjt+8u9oMXStzOKASDnpNpXAPKNWQdr6nCqMJj dNJS6USVVMRlb5VrsiZjxk0MEVL6jzWwW9qWFG9asnuX31pch4W+MSHHx/xmRxqMEgmY Siwca1iuLtj4lECh6L2P/J27zIKTdEPoa5a3Ez+BIC1I9AncmexhATU0WseAsvP/Xv94 lKEEGSrPD7XaKl5BsMu10eDahfLg9b0g8gOZJlaXsYofWiJYzqgijaiSTw+dmjtxR1r6 GsDg== X-Gm-Message-State: AA+aEWbuoNY5BhpuXDq2akoG5JHfVCejUBhOEKt3jKB3rgg0qgyO9bqp Vi6ub2Oapb0eN1mT0pal+aizUgZnoOJsaB1LrBjBHJd4gVg= X-Google-Smtp-Source: AFSGD/VgFJaaYtGtqAYo98LhhAf47yGL57Na4/yuyThY9jWQebcQBTTSMbyxtQ/wXUIlWdu5DmCXisM2QhqOzDHF6aY= X-Received: by 2002:aca:d905:: with SMTP id q5mr8605934oig.0.1544471009304; Mon, 10 Dec 2018 11:43:29 -0800 (PST) MIME-Version: 1.0 References: <154403054034.11544.3978949383914046587.stgit@ahduyck-desk1.jf.intel.com> <154403072403.11544.10419282512791659652.stgit@ahduyck-desk1.jf.intel.com> <15b6817fd945a1622afe673b46b028bacefad72b.camel@linux.intel.com> In-Reply-To: <15b6817fd945a1622afe673b46b028bacefad72b.camel@linux.intel.com> From: Dan Williams Date: Mon, 10 Dec 2018 11:43:17 -0800 Message-ID: Subject: Re: [driver-core PATCH v8 2/9] driver core: Establish order of operations for device_add and device_del via bitflag To: alexander.h.duyck@linux.intel.com Cc: Linux Kernel Mailing List , Greg KH , "Luis R. Rodriguez" , linux-nvdimm , Tejun Heo , Andrew Morton , Linux-pm mailing list , jiangshanlai@gmail.com, "Rafael J. Wysocki" , "Brown, Len" , Pavel Machek , zwisler@kernel.org, Dave Jiang , bvanassche@acm.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 10, 2018 at 11:35 AM Alexander Duyck wrote: > > On Mon, 2018-12-10 at 10:58 -0800, Dan Williams wrote: > > On Wed, Dec 5, 2018 at 9:25 AM Alexander Duyck > > wrote: > > > > > > Add an additional bit flag to the device struct named "dead". > > > > > > This additional flag provides a guarantee that when a device_del is > > > executed on a given interface an async worker will not attempt to attach > > > the driver following the earlier device_del call. Previously this > > > guarantee was not present and could result in the device_del call > > > attempting to remove a driver from an interface only to have the async > > > worker attempt to probe the driver later when it finally completes the > > > asynchronous probe call. > > > > > > Signed-off-by: Alexander Duyck > > > --- > > > drivers/base/core.c | 11 +++++++++++ > > > drivers/base/dd.c | 8 ++++++-- > > > include/linux/device.h | 5 +++++ > > > 3 files changed, 22 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/base/core.c b/drivers/base/core.c > > > index f3e6ca4170b4..70358327303b 100644 > > > --- a/drivers/base/core.c > > > +++ b/drivers/base/core.c > > > @@ -2075,6 +2075,17 @@ void device_del(struct device *dev) > > > struct kobject *glue_dir = NULL; > > > struct class_interface *class_intf; > > > > > > + /* > > > + * Hold the device lock and set the "dead" flag to guarantee that > > > + * the update behavior is consistent with the other bitfields near > > > + * it and that we cannot have an asynchronous probe routine trying > > > + * to run while we are tearing out the bus/class/sysfs from > > > + * underneath the device. > > > + */ > > > + device_lock(dev); > > > + dev->dead = true; > > > + device_unlock(dev); > > > + > > > /* Notify clients of device removal. This call must come > > > * before dpm_sysfs_remove(). > > > */ > > > diff --git a/drivers/base/dd.c b/drivers/base/dd.c > > > index 88713f182086..3bb8c3e0f3da 100644 > > > --- a/drivers/base/dd.c > > > +++ b/drivers/base/dd.c > > > @@ -774,6 +774,10 @@ static void __device_attach_async_helper(void *_dev, async_cookie_t cookie) > > > > > > device_lock(dev); > > > > > > + /* device is or has been removed from the bus, just bail out */ > > > + if (dev->dead) > > > + goto out_unlock; > > > + > > > > What do you think about moving this check into > > __device_attach_driver() alongside all the other checks? That way we > > also get ->dead checking through the __device_attach() path. > > I'm not really sure that is the best spot to do that. Part of the > reason being that by placing it where I did we avoid messing with the > runtime power management for the parent if it was already powered off. ...but this already a rare event and the parent shouldn't otherwise be bothered by a spurious pm_runtime wakeup event. > If anything I would say we could probably look at pulling the check out > and placing the driver check in __device_attach_async_helper since from > what I can tell the check is actually redundant in the non-async path > anyway since __device_attach already had taken the device lock and > checked dev->driver prior to calling __device_attach_driver. > > > ...and after that maybe it could be made a common helper > > (dev_driver_checks()?) shared between __device_attach_driver() and > > __driver_attach() to reduce some duplication. > > I'm not sure consolidating it into a function would really be worth the > extra effort. It would essentially just obfuscate the checks and I am > not sure you really save much with: > if (dev_driver_checks(dev)) > vs: > if (!dev->dead && !dev->driver) > > By the time you create the function and replace the few spots that are > making these checks you would end up most likely adding more complexity > to the kernel rather than reducing it any. No, I was talking about removing this duplication in __device_attach_driver() and __driver_attach(): if (ret == 0) { /* no match */ return 0; } else if (ret == -EPROBE_DEFER) { dev_dbg(dev, "Device match requests probe deferral\n"); driver_deferred_probe_add(dev); } else if (ret < 0) { dev_dbg(dev, "Bus failed to match device: %d", ret); return ret; } /* ret > 0 means positive match */ ...and lead in with a dev->dead check.