On Tue, 2018-07-24 at 22:04 +0100, James Greenhalgh wrote: > > > I'd say this patch isn't desirable for trunk. I'd be interested in use cases > that need a static decision on presence of LSE that are not better expressed > using higher level language features. > > Thanks, > James
How about when building the higher level features? Right now, in sysdeps/aarch64/atomic-machine.h, we hardcode ATOMIC_EXCHANGE_USES_CAS to 0. If we had __ARM_FEATURE_LSE we could use that to determine if we wanted to set ATOMIC_EXCHANGE_USES_CAS to 0 or 1 which would affect the call generated in nptl/pthread_spin_lock.c. That would be useful if we built a lipthread specifically for a platform that had LSE. Steve Ellcey sell...@cavium.com
