Messages in this thread | | | Date | Mon, 7 Jan 2002 22:03:36 +0000 (GMT) | From | Matthew Kirkwood <> | Subject | Re: [PATCH][RFC] Lightweight user-level semaphores |
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On Mon, 7 Jan 2002, Linus Torvalds wrote:
> > * It leaks. How were you going to refcount the kernel > > portions? Could they be attached to the VM mapping? > > Would a lockfs be too expensive? > > Yes, I was going to just attach to the vma,
Wouldn't that have to be an address_space, so separate maps of the same object will use the same count? Or (not unlikely) am I misunderstanding the way these structures are laid out?
> along with potentially also require a flag at mmap time (MAP_SEMAPHORE > - some other unixes have something like it already) to tell the OS > about the consistency issues that might come up on some architectures > (on x86 it would be a no-op).
OK.
> > * It doesn't have a timeout. Is there something like a > > down_timeout() available? > > Not as-is, but all the kernel infrastructure should be there in > theory.
OK, thanks.
> > * I don't do the: > > > > if (kfs->user_address != fs) > > goto bad_sem; > > > > because it doesn't seem to add anything, and prevents > > putting these locks in a non-fixed file or SysV SHM > > map. > > Fair enough. I think I suggested that just as another sanity check, > and because some architectures _will_ require address issues (not > necessarily total equality, but at least "modulo X equality").
Should being in the same place in the same page (though possibly at a different address) should suffice for all architectures?
Matthew.
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