On Fri, Oct 20, 2017 at 01:00:14PM -0700, Matt Turner wrote: > On Fri, Oct 20, 2017 at 12:48 PM, Paul E. McKenney > <paulmck@xxxxxxxxxxxxxxxxxx> wrote: > > Hello, Michael, > > > > Do any of the DEC Alpha systems that run recent kernels have InfiniBand? > > Given my understanding of the history, I believe the answer to be "no". > > If I am wrong, please let me know, as I will otherwise interpret silence > > as assent. ;-) > > I'm not aware of any shipping with Infiniband, and I haven't heard of > anyone putting Infiniband in an Alpha. > > Why do you ask? :) Because the Linux-kernel InfiniBand driver contains a bunch of instances of smp_read_barrier_depends(), which matter only on Alpha. Plus the InfiniBand maintainers have not responded to queries about what these smp_read_barrier_depends() instances are supposed to do. Now it might be that they are just busy, or it might be that they don't know themselves. If Alpha doesn't use InfiniBand, they can simply be removed. On the other hand, if Alpha -did- use InfiniBand, it would be necessary to inspect the code to determine whether if READ_ONCE() needs to be added somewhere to make up for the removal of smp_read_barrier_depends(). The reason this came up to begin with is that Will Deacon is adding an smp_read_barrier_depends() to READ_ONCE() and Mark Rutland is converting all ACCESS_ONCE() instances to either READ_ONCE() or WRITE_ONCE(). With these changes, core code need not know about Alpha, and almost all instances of smp_read_barrier_depends() can be removed. Hey, you asked! ;-) Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-alpha" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
