Messages in this thread | | | Date | Mon, 7 Jan 2002 12:28:31 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: [PATCH][RFC] Lightweight user-level semaphores |
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On Mon, 7 Jan 2002, Matthew Kirkwood 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, 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).
> * 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.
> * 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").
Linus
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