On Tue, 5 Dec 2006 17:48:05 +0000 (GMT) "Maciej W. Rozycki" <[EMAIL PROTECTED]> wrote:
> Essentially there is a race when disconnecting from a PHY, because > interrupt delivery uses the event queue for processing. The function to > handle interrupts that is called from the event queue is phy_change(). > It takes a pointer to a structure that is associated with the PHY. At the > time phy_stop_interrupts() is called there may be one or more calls to > phy_change() still pending on the event queue. They may not be able to be > processed until the structure passed to phy_change() have been freed, at > which point calling the function is wrong. > > One way of avoiding it is calling flush_scheduled_work() from > phy_stop_interrupts(). This is fine as long as a caller of > phy_stop_interrupts() (not necessarily the immediate one calling into > libphy) does not hold the netlink lock. So let me try to rephrase... - phy_change() is the workqueue callback function. It is executed by keventd. - Something under phy_change() takes rtnl_lock() (but what??) - phy_stop_interrupts() does flush_scheduled_work(). This has to following logic: - if I am kevetnd, run phy_change() directly. - If I am not keventd, wait for keventd() to run phy_change() - So if the caller of phy_stop_interrupt() already holds rtnl_lock(), and if that caller is keventd then it will recur onto rntl_lock() and will deadlock. Problem is, if the caller of phy_stop_interrupt() is *not* keventd, that caller will still deadlock, because that caller is waiting for keventd to run phy_change(), and keventd cannot do that, because the not-keventd process already holds rtnl_lock. Now, afaict, there are only two callers of phy_stop_interrupts(): the close() handlers of gianfar.c and fs_enet-main.c (confusingly held in netdevice.stop (confusingly called by dev_close())). Via phy_disconnect. Did I miss anything? And the dev_close() caller holds rtnl_lock. Summary: a) Please tell us what code under phy_change() wants to take rtnl_lock b) I think it should deadlock whether or not the caller of phy_stop_interrupt() is keventd. What am I missing? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
