On Mon, 2015-09-07 at 18:23 +0200, Mian Yousaf Kaukab wrote: > urb completion callback is executed in host controllers interrupt > context. To keep preempt disable time short, add urbs to a list on > completion and schedule work to process the list. > > Moreover, save timestamp and sof number in the urb completion callback > to avoid any delays. > > Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@xxxxxxxxx> > --- > History: > v1: > - Use global work queue instead of creating ordered queue. 1. using a common queue for real-time work is probably not nice for picture quality 2. it will deadlock under some conditions The explanation is a bit long Suppose we have a device with a camera and a storage device, like an ordinary camera you can use as a video device which also exports its memory card. Now we assume that the storage part is suspended. CPU A CPU B work item scheduled entering uvc_uninit_video() work item executed work item allocates memory write to storage interface storage interface being resumed flush_work() - waiting for CPU B DEADLOCK If you want to use flush_work() you must use a dedicated queue. Regards Oliver -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
