Messages in this thread | | | Subject | Re: [driver-core PATCH v5 4/9] driver core: Move async_synchronize_full call | From | Alexander Duyck <> | Date | Tue, 06 Nov 2018 08:18:43 -0800 |
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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
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