Hi, On 4/29/21 2:04 PM, Daniel Vetter wrote: > On Thu, Apr 29, 2021 at 01:54:46PM +0200, Greg Kroah-Hartman wrote: >> On Thu, Apr 29, 2021 at 01:40:28PM +0200, Daniel Vetter wrote: >>> On Wed, Apr 28, 2021 at 11:52:49PM +0200, Hans de Goede wrote: >>>> Userspace could hold open a reference to the connector->kdev device, >>>> through e.g. holding a sysfs-atrtribute open after >>>> drm_sysfs_connector_remove() has been called. In this case the connector >>>> could be free-ed while the connector->kdev device's drvdata is still >>>> pointing to it. >>>> >>>> Give drm_connector devices there own device type, which allows >>>> us to specify our own release function and make drm_sysfs_connector_add() >>>> take a reference on the connector object, and have the new release >>>> function put the reference when the device is released. >>>> >>>> Giving drm_connector devices there own device type, will also allow >>>> checking if a device is a drm_connector device with a >>>> "if (device->type == &drm_sysfs_device_connector)" check. >>>> >>>> Note that the setting of the name member of the device_type struct will >>>> cause udev events for drm_connector-s to now contain DEVTYPE=drm_connector >>>> as extra info. So this extends the uevent part of the userspace API. >>>> >>>> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> >>> >>> Are you sure? I thought sysfs is supposed to flush out any pending >>> operations (they complete fast) and handle open fd internally? >> >> Yes, it "should" :) > > Thanks for confirming my vague memories :-) > > Hans, pls drop this one. Please see my earlier reply to your review of this patch, it is still needed but for a different reason: """ We still need this change though to make sure that the "drm/connector: Add drm_connector_find_by_fwnode() function" does not end up following a dangling drvdat pointer from one if the drm_connector kdev-s. The class_dev_iter_init() in drm_connector_find_by_fwnode() gets a reference on all devices and between getting that reference and it calling drm_connector_get() - drm_connector_unregister() may run and drop the possibly last reference to the drm_connector object, freeing it and leaving the kdev's drvdata as a dangling pointer. """ This is actually why I added it initially, and while adding it I came up with this wrong theory of why it was necessary independently of the drm_connector_find_by_fwnode() addition, sorry about that. Regards, Hans _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
