Messages in this thread | | | Date | Wed, 14 Jul 2004 23:47:13 +0530 | From | Dipankar Sarma <> | Subject | Re: [RFC] Refcounting of objects part of a lockfree collection |
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On Wed, Jul 14, 2004 at 10:08:00AM -0700, Greg KH wrote: > On Wed, Jul 14, 2004 at 02:27:58PM +0530, Ravikiran G Thirumalai wrote: > > might be a bit yucky to assume atomic_t internals, but it is just one header > > file :) <ducks> > > I still think you need to fix this, manipulating atomic_t variables by > hand is not always guaranteed to work on all arches, from what I > remember.
AFAICS, the hash-locked refcounting grabs a spin lock for all operations on the atomic_t. Any reason why that should not be safe ? Of course, I can't see why we can't have two versions of the reference counter depending on __HAVE_ARCH_CMPXCHG. Kiran ?
> > And what arches do not support cmpxchg? How does this change affect the > performance of them?
mips64, smp arm ?? ;-)
With a hashed lock, it should not be all that bad in low-end SMPs. Besides we already use such a thing in gettimeofday implementation with a global lock. However this is a valid issue and performance #s from those arch users would be useful.
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