Messages in this thread | | | Date | Fri, 22 May 2009 16:30:20 +0300 | Subject | Re: How to tell whether a struct file is held by a process? | From | Pantelis Koukousoulas <> |
| |
The only problem I find with leaving mutual exclusion 100% to userspace and burdening the kernel only with the decision of whether a port should be handled by kernel or userspace is this:
Suppose a device needs a reset as part of its init sequence (a whole lot of them do, this is not purely hypothetical). Then a different process may get to operate the device before and after the reset and hilarity may result from that.
There is also the issue of a Program (as in Vmware, Qemu etc, not as in pid) thinking it has claimed a port and then finding the device just connected there is actually unavailable to operate, but this doesn't sound that bad. (After all, the device itself might have been broken, having claimed a port in no way guarantees success in operating devices connected there).
So, if there is a clean / acceptable way to handle the reset issue in userspace I 'm happy to dispose with kernel-level checks for 'allowed processes' altogether.
Does that sound reasonable?
Thanks a lot for the discussion, Pantelis
| |