On Sun, 2004-04-04 at 14:16, David Brownell wrote: > You're assuming that synchronization is there to establish a single > global notion of state. Clearly that's impossible; also undesirable.
Thank you. > The synchronization is actually there to let the "device gone" state > spread cleanly through the software stack. By the time USB disconnect() > is called, host controller drivers (and khubd) have normally cleaned up > all hardware state, and usbcore is never going to accept another operation > on that device. The disconnect() callback is there to prevent that > raciness from making trouble ... closing windows from the bottom up. So you dispute this assertion in the email you quoted above: On Sun, 2004-04-04 at 14:16, David Brownell wrote: > James Bottomley wrote: > > Since we cannot solve that > > race, there's no reason to try to solve the "some parts of the kernel > > know but others don't" part of the race. On what basis? This, I think, is the core of the differences between us. I don't see why an asynchronous event should proceed up the stack in an orderly synchronised manner. It goes like this: - Initially, only the device knows, so commands outstanding time out - Then, the USB driver knows, so it errors incoming commands (and presumably returns with error any outstanding untimed out ones) - Then, SCSI knows, so we forbid user I/O The point is, that any I/O after disconnection gets an error ... the error just comes from different places as the knowledge propagates upwards. > The way usb-storage passes that up to the SCSI layer is by calling > scsi_remove_host(). Bug 2400 shows up later, through the block > layer (or is it just cdrom?) code. Did someone actually post the > specific source code line in cdrom_release() that's oopsing? Well, someone posted a patch a lot earlier in the thread ... we're on to general hotplug principles now. James ------------------------------------------------------- This SF.Net email is sponsored by: IBM Linux Tutorials Free Linux tutorial presented by Daniel Robbins, President and CEO of GenToo technologies. Learn everything from fundamentals to system administration.http://ads.osdn.com/?ad_id=1470&alloc_id=3638&op=click _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
