On Tue, 18 May 2004, David Brownell wrote: > Alan Stern wrote: > > > > I'm all in favor of something like this. Do you have any ideas on how we > > should handle the case where the hub itself was disconnected but we don't > > yet know that it's gone? We wouldn't want to log a KERN_ALERT message > > when that happens. > > The only potential problem is where states are represented as > call stack context in khubd ... so long as there's only one > khubd thread noticing disconnects, there's no way it'd notice > and then communicate (to itself) that disconnect. Right?
I don't understand your point here. Imagine this: hub A reports a new connection on one of its ports. Khubd sees this and goes through debouncing etc. While this is happening hub A is unplugged. Since debouncing failed, khubd wants to disable the port. But it can't, since hub A won't reply to the CLEAR_FEATURE messages. Since khubd has been preoccupied with all this debouncing stuff it doesn't yet know that hub A has been unplugged. Even if it's multithreaded it still might not learn for a large fraction of a second, not until hub A's parent's status interrupt message arrives. In the meantime, how do we know to avoid logging a premature KERN_ALERT message? > Other than multithreading khubd, or switching it to a pure state > machine model, the first thing that comes to mind is that the > status change interrupt says which ports changed status, and > they all seem to imply "disconnect" for any device connected > on that port. (Except for remote wakeup signaling, which would > preclude talking to a downstream hub.) So that completion handler > could mark everything NOTATTACHED right away, so retries lasting > more than 1/4 sec could notice that's the case ... and avoid the > nasty log messages). They don't all imply disconnect. C_PORT_RESET and C_PORT_SUSPEND don't, for example. So that idea doesn't work. Alan Stern ------------------------------------------------------- This SF.Net email is sponsored by: SourceForge.net Broadband Sign-up now for SourceForge Broadband and get the fastest 6.0/768 connection for only $19.95/mo for the first 3 months! http://ads.osdn.com/?ad_id=2562&alloc_id=6184&op=click _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
