On Mon, Mar 17, 2025 at 08:22:35AM -1000, Tejun Heo wrote: ... > > + /* > > + * If the task is allowed to run on all CPUs, simply use the > > + * architecture's cpumask directly. Otherwise, compute the > > + * intersection of the architecture's cpumask and the task's > > + * allowed cpumask. > > + */ > > + if (!cpus || p->nr_cpus_allowed >= num_possible_cpus() || > > + cpumask_subset(cpus, p->cpus_ptr)) > > + return cpus; > > + > > + if (!cpumask_equal(cpus, p->cpus_ptr) && > > Hmm... isn't this covered by the preceding cpumask_subset() test? Here, cpus > is not a subset of p->cpus_ptr, so how can it be the same as p->cpus_ptr? > > > + cpumask_and(local_cpus, cpus, p->cpus_ptr)) > > + return local_cpus; > > + > > + return NULL; Also, I'm also wondering if there's really a benefit checking for cpumask_subset() and then doing cpumask_and() only when it's needed, or if we should just do cpumask_and(). It's true that we can save some writes, but they're done on a temporary local per-CPU cpumask, so they shouldn't introduce cache contention. -Andrea
