lkml.org 
[lkml]   [2018]   [Nov]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [driver-core PATCH v5 4/9] driver core: Move async_synchronize_full call
    From
    Date
    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

    \
     
     \ /
      Last update: 2018-11-06 17:18    [W:8.686 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site