From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-f195.google.com (mail-pl1-f195.google.com [209.85.214.195]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id E0B6321164EF2 for ; Tue, 6 Nov 2018 09:22:26 -0800 (PST) Received: by mail-pl1-f195.google.com with SMTP id s5-v6so6500162plq.11 for ; Tue, 06 Nov 2018 09:22:26 -0800 (PST) Message-ID: <1541524943.196084.178.camel@acm.org> Subject: Re: [driver-core PATCH v5 4/9] driver core: Move async_synchronize_full call From: Bart Van Assche Date: Tue, 06 Nov 2018 09:22:23 -0800 In-Reply-To: References: <154145223352.29224.8912797012647157172.stgit@ahduyck-desk1.jf.intel.com> <154145231976.29224.39638353241256116.stgit@ahduyck-desk1.jf.intel.com> <1541466289.196084.176.camel@acm.org> Mime-Version: 1.0 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: Alexander Duyck , linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org Cc: len.brown@intel.com, linux-pm@vger.kernel.org, rafael@kernel.org, jiangshanlai@gmail.com, linux-nvdimm@lists.01.org, pavel@ucw.cz, zwisler@kernel.org, tj@kernel.org, akpm@linux-foundation.org List-ID: On Tue, 2018-11-06 at 08:18 -0800, Alexander Duyck wrote: > On Mon, 2018-11-05 at 17:04 -0800, Bart Van Assche wrote: > > On Mon, 2018-11-05 at 13:11 -0800, Alexander Duyck wrote: > > > This patch moves the async_synchronize_full call out of > > > __device_release_driver and into driver_detach. > > > > > > The idea behind this is that the async_synchronize_full call will only > > > guarantee that any existing async operations are flushed. This doesn't do > > > anything to guarantee that a hotplug event that may occur while we are > > > doing the release of the driver will not be asynchronously scheduled. > > > > > > By moving this into the driver_detach path we can avoid potential deadlocks > > > as we aren't holding the device lock at this point and we should not have > > > the driver we want to flush loaded so the flush will take care of any > > > asynchronous events the driver we are detaching might have scheduled. > > > > > > Signed-off-by: Alexander Duyck > > > --- > > > drivers/base/dd.c | 6 +++--- > > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > > > diff --git a/drivers/base/dd.c b/drivers/base/dd.c > > > index 76c40fe69463..e74cefeb5b69 100644 > > > --- a/drivers/base/dd.c > > > +++ b/drivers/base/dd.c > > > @@ -975,9 +975,6 @@ static void __device_release_driver(struct device *dev, struct device *parent) > > > > > > drv = dev->driver; > > > if (drv) { > > > - if (driver_allows_async_probing(drv)) > > > - async_synchronize_full(); > > > - > > > while (device_links_busy(dev)) { > > > __device_driver_unlock(dev, parent); > > > > > > @@ -1087,6 +1084,9 @@ void driver_detach(struct device_driver *drv) > > > struct device_private *dev_prv; > > > struct device *dev; > > > > > > + if (driver_allows_async_probing(drv)) > > > + async_synchronize_full(); > > > + > > > for (;;) { > > > spin_lock(&drv->p->klist_devices.k_lock); > > > if (list_empty(&drv->p->klist_devices.k_list)) { > > > > Have you considered to move that async_synchronize_full() call into > > bus_remove_driver()? Verifying the correctness of this patch requires to > > check whether the async_synchronize_full() comes after the > > klist_remove(&drv->p->knode_bus) call. That verification is easier when > > the async_synchronize_full() call occurs in bus_remove_driver() instead > > of in driver_detach(). > > I considered it, however it ends up with things being more symmetric to > have use take care of synchronizing things in driver_detach since after > this patch set we are scheduling thing asynchronously in driver_attach. > > Also I don't think it would be any great risk simply because calling > driver_detach with the driver still associated with the bus would be a > blatent error as it could easily lead to issues where you unbind a > driver but have it get hotplugged to a device while that is going on. Thanks for the additional clarification. Since I'm fine with this patch: Reviewed-by: Bart Van Assche _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm