On 18 Jul 2006, at 10:56, Arjan van de Ven wrote: >> plain text document attachment (synch-ops) >> Add "always lock'd" implementations of set_bit, clear_bit and >> change_bit and the corresponding test_and_ functions. Also add >> "always lock'd" implementation of cmpxchg. These give guaranteed >> strong synchronisation and are required for non-SMP kernels running on >> an SMP hypervisor. > > Hi, > > this sounds really like the wrong approach; you know you're compiling > for xen, so why not just make set_bit() and the others use the lock'd > instructions at compile time? Then all users of bitops would unnecessarily pay the price when running in a single-CPU guest. Only a few of our bitops callers absolutely require the lock prefix in all cases. -- Keir
