* Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote: > I can't see a neater way down this path, and I don't want to lose > const. > > I can see three alternatives: > 1) An ONSTACK_CPUMASK(name) macro which declares "struct cpumask name[1]" or > "struct cpumask *name". Same idea as yours, without the typedef. > 2) Use a normal struct for cpumask, make everyone use pointers, but have an > struct cpumask *alloc_stack_cpumask() which uses alloca() for small > NR_CPUS. > 3) Same, but just use kmalloc everywhere. Optimize important cases by hand. > > Anyone see a better way? since most of the important cpumasks in high-perf codepaths are already pre-constructed and embedded in some existing object (say task_struct), i think a variant of #3 is the best approach: - get rid of cpumask_t and use 'struct cpumask' everywhere. - do not expose normal kernel code to struct cpumask's definition, only declare the type via 'struct cpumask;' in sched.h - a'la kmem_cache_t. - even hide the structure from sched.h - use an extra indirection for struct cpumask *cpus_allowed in task_struct and be done with it. - have normal cpumask object alloc/free codepaths. - optimize any remaining important cases by hand, if needed. (the scheduler mostly) (wrt. #2, alloca() is a nightmare i think.) Ingo -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
