Messages in this thread | | | Subject | Re: [PATCH] Lightweight userspace semaphores... | From | (Eric W. Biederman) | Date | 28 Feb 2002 21:44:40 -0700 |
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Hubertus Franke <frankeh@watson.ibm.com> writes:
> Rusty, since I supplied one of those packages available under > lse.sourceforge.net > > let me make some comments. > > (a) why do you need to pin. I simply use the user level address (vaddr) > and hash with the <mm,vaddr> to obtain the internal object. > This also gives me full protection through the general vmm mechanisms.
Do: if (page->mapping) hash(page->mapping, page->offset, vaddr & ~PAGE_MASK) else hash(mm, vaddr) This handles the semaphores in shared memory case. So the semaphores will work across processes as well.
> (c) creation can be done on demand, that's what I do. If you never have > to synchronize through the kernel than you don't create the objects. > There should be an option to force explicite creation if desired.
Which makes the uncontended (common) case fast.
> (d) The kernel should simply provide waiting and wakeup functionality and > the bean counting should be done in user space. There is no need to > pin or crossmap.
Agreed.
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