On 4/19/07, Alan Stern <[EMAIL PROTECTED]> wrote:
Among the worst offenders are character devices. None of the subsystem providers offering char device registration performs immediate detach -- they are a lot like sysfs used to be. (In fact, they probably _can't_ provide it since read() or write() calls can block indefinitely in the lower-level driver; the subsystem may have no way to force them to fail-fast.)
That shoudl be doable - the read/write routines should check if device is still alive and return immideately when device is dead. When disconnecting device just wake up all readers and writers and they should eventually fall off. Hmm, I guess am starting to think that using refcounting everywhere is not a good idea. We are trying to have "immediate disconnect" behavior and refcounting is an antithesis of it. Refcounting works well when it is contained - register grabs reference; unregister puts it back; but there is no passing references down between the layers. When device is being removed it needs to signal downstream that it is gone and should not be accessed anymore. And we need to do that anyway because if device is really gone but its users ignore it they will get endless stream of errors when trying to access it. -- Dmitry - 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/
