On Thu, Jan 16, 2025 at 09:02:16PM +0000, Matthew Wilcox wrote: > On Thu, Jan 16, 2025 at 12:02:34PM -0800, Paul E. McKenney wrote: > > +The special cases where it makes sense do obtain a per-CPU pointer in > > s/do/to/ > > > +preemptible code are addressed by raw_cpu_ptr(), but please note that such > > s/please note that // Good eyes, thank you! I am a bit sorry to see the "please note that" go, but I suppose fewer words is a good thing. I will fix these on my next rebase and repost. Thanx, Paul > > +use cases need to handle cases where two different CPUs are accessing > > +the same per cpu variable, which might well be that of a third CPU. > > +These use cases are typically performance optimizations. For example, > > +SRCU implements a pair of counters as a pair of per-CPU variables, > > +and rcu_read_lock_nmisafe() uses raw_cpu_ptr() to get a pointer to some > > +CPU's counter, and uses atomic_inc_long() to handle migration between > > +the raw_cpu_ptr() and the atomic_inc_long().
