Christoph Lameter wrote on Tuesday, March 28, 2006 3:48 PM > On Tue, 28 Mar 2006, Zoltan Menyhart wrote: > > > Why not to use separate bit operations for different purposes? > > > > - e.g. "test_and_set_bit_N_acquire()" for lock acquisition > > - "test_and_set_bit()", "clear_bit()" as they are today > > - "release_N_clear_bit()"... > > > > That would force IA64 specifics onto all other architectures. > > Could we simply define these smb_mb__*_clear_bit to be noops > and then make the atomic bit ops to have full barriers? That would satisfy > Nick's objections. > > --- linux-2.6.16.orig/include/asm-ia64/bitops.h 2006-03-19 21:53:29.000000000 -0800 > +++ linux-2.6.16/include/asm-ia64/bitops.h 2006-03-28 15:45:08.000000000 -0800 > @@ -45,6 +45,7 @@ > old = *m; > new = old | bit; > } while (cmpxchg_acq(m, old, new) != old); > + smb_mb(); > } There are better way to do it. The pointer is already cast as volatile, so old = *m has acq semantics built-in, we can just change cmpxchg_acq to cmpxchg_rel, then effectively it is a full memory barrier without doing the expensive smp_mb(). - Ken - : send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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