On Fri, 17 Jul 2015, Peter Chen wrote: > There are several benefits for doing like this: > > - hc_driver can be customized for each hcd > - Other hcd hc_driver's initialization will not affect current one. > We run out NULL pointer dereference problem when one hcd is started > by module_init, and the other is started by otg thread at SMP platform. > The reason for this problem is ehci_init_driver will do memory copy > for current uniform hc_driver, and this memory copy will do memset (as 0) > first, so when the first hcd is running usb_add_hcd, and the second > hcd may clear the uniform hc_driver's space (at ehci_init_driver), > then the first hcd will meet NULL pointer at the same time. It seems to me the real problem is that ehci_init_driver gets called at the wrong time. It's not supposed to be called whenever a new host controller is initialized; rather, it should be called just once when the driver is initialized. This means the call should be in a module_init routine in host.c, not in ci_hdrc_host_init. If you need to customize the hc_driver structure for each host controller then yes, a separate copy is needed. But otherwise there's no need to make a copy. Alan Stern -- 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
