On Wed, 20 Nov 2019 13:47:00 -0500 (EST) Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > + if (rp->mmap_active) > > + return -EBUSY; > Like that, yes, but the test has to be made while fetch_lock is held. Certainly, thanks. I was rushing just to add a postscriptum. > Incidentally, the comment for fetch_lock says that it protects b_read > and b_out, but mon_bin_vma_fault doesn't use either of those fields. I probably should change that comment to "protect the integrity of the circular buffer, such as b_out". Anyway... If you are looking at it too, what do you think about not using any locks in mon_bin_vma_fault() at all? Isn't it valid? I think I tried to be "safe", but it only uses things that are constants unless we're opening and closing; a process cannot make page faults unless it has some thing mapped; and that is only possible if device is open and stays open. Can you find a hole in this reasoning? -- Pete
