On Fri, 11 Aug 2006, Greg KH wrote: > > As I see it, there's no advantage in making register_root_hub run in a > > new thread. There _is_ an advantage in making the call from the hub > > driver run in a new thread, but there are also dangers. Just as one > > example, what's to prevent someone from doing "rmmod usbcore" while these > > sub-threads are still running? > > Here's an updated version that prevents that from happening. > > I'll look into moving this further up the call chain so that the root > hub stuff is not affected by this.
I think the best approach would be to put the entire second half of hub_port_connect_change (i.e., the big loop that runs SET_CONFIG_TRIES times) into the sub-thread. Then usb_new_device could be left as is, which will avoid problems with HCDs registering their root hubs. To avoid the other possible problems, khubd should arrange to wait until all the sub-threads have ended before calling usb_unlock_device. That's the main requirement: The parent hub must remain locked during the entire time its children are being probed. This would mean that all the devices attached to a hub could be probed in parallel, but separate hubs would still be serialized. Sound good? I could work on a patch next week. To make things even more parallel would require running several main khubd threads, so that multiple hubs could be handled at the same time. We have considered the possibility of doing this at various times in the past. Implementing it would not be technically difficult at all. The real difficulty lies in deciding how many threads there should be, when to create them, and when to destroy them. For example, on my work computer I've got 7 USB buses but there's never more than one or two USB devices attached, so having one thread per bus would be tremendous overkill. Alan Stern ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
