Messages in this thread | | | Date | Fri, 18 Jan 2019 16:54:25 +0100 | From | Greg KH <> | Subject | Re: [driver-core PATCH v9 1/9] driver core: Establish order of operations for device_add and device_del via bitflag |
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On Wed, Dec 12, 2018 at 04:44:58PM -0800, 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. > > One additional change added was that I pulled the check for dev->driver > out of the __device_attach_driver call and instead placed it in the > __device_attach_async_helper call. This was motivated by the fact that the > only other caller of this, __device_attach, had already taken the > device_lock() and checked for dev->driver. Instead of testing for this > twice in this path it makes more sense to just consolidate the dev->dead > and dev->driver checks together into one set of checks. > > Reviewed-by: Dan Williams <dan.j.williams@intel.com> > Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com> > Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > --- > drivers/base/core.c | 11 +++++++++++ > drivers/base/dd.c | 22 +++++++++++----------- > include/linux/device.h | 5 +++++ > 3 files changed, 27 insertions(+), 11 deletions(-) > > diff --git a/drivers/base/core.c b/drivers/base/core.c > index 0073b09bb99f..950e25495726 100644 > --- a/drivers/base/core.c > +++ b/drivers/base/core.c > @@ -2080,6 +2080,17 @@ 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..74c194ac99df 100644 > --- a/drivers/base/dd.c > +++ b/drivers/base/dd.c > @@ -731,15 +731,6 @@ static int __device_attach_driver(struct device_driver *drv, void *_data) > bool async_allowed; > int ret; > > - /* > - * Check if device has already been claimed. This may > - * happen with driver loading, device discovery/registration, > - * and deferred probe processing happens all at once with > - * multiple threads. > - */ > - if (dev->driver) > - return -EBUSY; > - > ret = driver_match_device(drv, dev); > if (ret == 0) { > /* no match */ > @@ -774,6 +765,15 @@ static void __device_attach_async_helper(void *_dev, async_cookie_t cookie) > > device_lock(dev); > > + /* > + * Check if device has already been removed or claimed. This may > + * happen with driver loading, device discovery/registration, > + * and deferred probe processing happens all at once with > + * multiple threads. > + */ > + if (dev->dead || dev->driver) > + goto out_unlock; > + > if (dev->parent) > pm_runtime_get_sync(dev->parent); > > @@ -784,7 +784,7 @@ static void __device_attach_async_helper(void *_dev, async_cookie_t cookie) > > if (dev->parent) > pm_runtime_put(dev->parent); > - > +out_unlock: > device_unlock(dev); > > put_device(dev); > @@ -897,7 +897,7 @@ static int __driver_attach(struct device *dev, void *data) > if (dev->parent && dev->bus->need_parent_lock) > device_lock(dev->parent); > device_lock(dev); > - if (!dev->driver) > + if (!dev->dead && !dev->driver) > driver_probe_device(drv, dev); > device_unlock(dev); > if (dev->parent && dev->bus->need_parent_lock) > diff --git a/include/linux/device.h b/include/linux/device.h > index 1b25c7a43f4c..f73dad81e811 100644 > --- a/include/linux/device.h > +++ b/include/linux/device.h > @@ -957,6 +957,10 @@ struct dev_links_info { > * device. > * @dma_coherent: this particular device is dma coherent, even if the > * architecture supports non-coherent devices. > + * @dead: This device is currently either in the process of or has > + * been removed from the system. Any asynchronous events > + * scheduled for this device should exit without taking any > + * action. > * > * At the lowest level, every device in a Linux system is represented by an > * instance of struct device. The device structure contains the information > @@ -1051,6 +1055,7 @@ struct device { > defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL) > bool dma_coherent:1; > #endif > + bool dead:1;
This really should live in the struct device_private structure, as nothing outside of the driver core should care about this, or touch it.
A number of other bitfields should also move there as well, your's isn't the only one that I missed this for.
So can you make that quick change, and rebase (you needed to for patch 2 anyway), and resend so I can get this into my -next tree for people to start testing and basing their work on?
sorry this has taken so long, and thanks for sticking with it.
greg k-h
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