Hello, On Tue, Mar 18, 2025 at 08:31:29AM +0100, Andrea Righi wrote: > 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. Yeah, I can imagine it going either way, so no strong preference. Thanks. -- tejun
