Hello, I noticed that there could potentially be a sort of race condition in ohci-hcd.c file, related to interrupt handling. This caused Oops when removing ohci_hcd driver on one device I was working with - OHCI cell on SAMCOP chip used in ipaq h5000 devices. Please Cc: me as I am not subscribed to linux-usb-devel. Bugreport below:
Summary: ohci-hcd module can possibly crash when unloading due race condition. Description: In usb_remove_hcd there is possible place where race condition can occur. Problematic is caused by usb_hcd_poll_rh_status, which is normally called periodically from timer, or from ohci_irq handler. Removing HCD uses roughly following algorithm: 1) delete rh_timer, so it should not be called again 2) call ohci_stop, which does some magic and then disables interrupts. The problem is within the "some magic" part. Its execution takes some time and within this time, OHCI irq can possibly occur. This results in call of usb_hcd_poll_rh_status, which again calls timer_mod and re-enables rh_timer. Consecutively, we now have ohci driver which is short before unloading, but has active timer. This results in paging fault. It is possible that the interrupt occurs because of ohci_usb_reset called just prior to disabling interrupts, but I have no idea whether this is real. This problem also might or might not be visible depending on debugging turned on or off. Milan Plzik ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel