From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
To: Bart Van Assche <bvanassche@acm.org>,
linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org
Cc: linux-nvdimm@lists.01.org, tj@kernel.org,
akpm@linux-foundation.org, linux-pm@vger.kernel.org,
jiangshanlai@gmail.com, rafael@kernel.org, len.brown@intel.com,
pavel@ucw.cz, zwisler@kernel.org, dan.j.williams@intel.com,
dave.jiang@intel.com
Subject: Re: [driver-core PATCH v5 4/9] driver core: Move async_synchronize_full call
Date: Tue, 06 Nov 2018 08:18:43 -0800 [thread overview]
Message-ID: <e2fec0e159757f31abbd258e284a844d0d8a2859.camel@linux.intel.com> (raw)
In-Reply-To: <1541466289.196084.176.camel@acm.org>
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 <alexander.h.duyck@linux.intel.com>
> > ---
> > 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().
>
> Thanks,
>
> Bart.
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.
- Alex
next prev parent reply other threads:[~2018-11-06 16:18 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-05 21:11 [driver-core PATCH v5 0/9] Add NUMA aware async_schedule calls Alexander Duyck
2018-11-05 21:11 ` [driver-core PATCH v5 1/9] workqueue: Provide queue_work_node to queue work near a given NUMA node Alexander Duyck
2018-11-06 0:42 ` Bart Van Assche
2018-11-06 16:27 ` Alexander Duyck
2018-11-05 21:11 ` [driver-core PATCH v5 2/9] async: Add support for queueing on specific " Alexander Duyck
2018-11-07 0:50 ` Bart Van Assche
2018-11-05 21:11 ` [driver-core PATCH v5 3/9] device core: Consolidate locking and unlocking of parent and device Alexander Duyck
2018-11-05 21:11 ` [driver-core PATCH v5 4/9] driver core: Move async_synchronize_full call Alexander Duyck
2018-11-06 1:04 ` Bart Van Assche
2018-11-06 16:18 ` Alexander Duyck [this message]
2018-11-06 17:22 ` Bart Van Assche
2018-11-05 21:12 ` [driver-core PATCH v5 5/9] driver core: Establish clear order of operations for deferred probe and remove Alexander Duyck
2018-11-06 4:10 ` kbuild test robot
2018-11-06 23:51 ` Bart Van Assche
2018-11-07 0:52 ` Alexander Duyck
2018-11-23 1:23 ` Rong Chen
2018-11-23 14:19 ` Bart Van Assche
2018-11-06 23:48 ` Bart Van Assche
2018-11-07 1:34 ` Joe Perches
2018-11-08 23:42 ` Bart Van Assche
2018-11-11 14:31 ` Pavel Machek
2018-11-27 2:35 ` Dan Williams
2018-11-27 16:49 ` Alexander Duyck
2018-11-05 21:12 ` [driver-core PATCH v5 6/9] driver core: Probe devices asynchronously instead of the driver Alexander Duyck
2018-11-07 0:22 ` Bart Van Assche
2018-11-05 21:12 ` [driver-core PATCH v5 7/9] driver core: Attach devices on CPU local to device node Alexander Duyck
2018-11-07 0:24 ` Bart Van Assche
2018-11-05 21:12 ` [driver-core PATCH v5 8/9] PM core: Use new async_schedule_dev command Alexander Duyck
2018-11-07 0:24 ` Bart Van Assche
2018-11-05 21:12 ` [driver-core PATCH v5 9/9] libnvdimm: Schedule device registration on node local to the device Alexander Duyck
2018-11-07 0:26 ` Bart Van Assche
2018-11-06 0:50 ` [driver-core PATCH v5 0/9] Add NUMA aware async_schedule calls Bart Van Assche
2018-11-06 16:25 ` Alexander Duyck
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