On Sat, May 9, 2009 at 19:15, Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> wrote: >> > Yes. That is, a process shouldn't be allowed to access a locked device >> > unless that process is the lock holder. >> >> You think the pid or the uid would make more sense? > > How about neither ? > > The standard Unix behaviour is to open the file O_EXCL if you want > exclusivity. Neither uid or pid are helpful or work in the many > environments where you want security - in particular where (as is very > common with user space driver type code) you want parts of your code > running setuid and parts not, as two processes with different pid and uid > values. > > If O_EXCL is interpeted as exclusive access (versus kernel and re-open of > the same node) then you can implement the rest of the sematics in user > space. Hmm, but his is a lock for "future" device, which did not even show up at that point the "lock" will be taken. The files would not be opened a second time. The lock-file and the device file are two different files, both would be opened only by one process - and we are playing around here with the idea how to connect these both processes. Thanks, Kay -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html