nr_cpu_ids is the (badly named) runtime limit on possible CPU numbers; ie. the variable version of NR_CPUS. This makes is valid in all configs, including UP. From: Rusty Russell Signed-off-by: Rusty Russell Signed-off-by: Mike Travis --- include/linux/cpumask.h | 10 ++++++++-- init/main.c | 7 +++++++ 2 files changed, 15 insertions(+), 2 deletions(-) --- test-compile.orig/include/linux/cpumask.h +++ test-compile/include/linux/cpumask.h @@ -195,6 +195,14 @@ extern cpumask_t _unused_cpumask_arg_; #define cpus_addr(src) ((src).bits) /* End deprecated region. */ +#if NR_CPUS <= BITS_PER_LONG +/* Constant is usually more efficient than a variable for small NR_CPUS */ +#define nr_cpu_ids NR_CPUS +#else +/* Starts at NR_CPUS until we know better. */ +extern int nr_cpu_ids; +#endif /* NR_CPUS > BITS_PER_LONG */ + static inline void cpumask_set_cpu(int cpu, volatile struct cpumask *dstp) { set_bit(cpu, dstp->bits); @@ -434,7 +442,6 @@ extern cpumask_t cpu_mask_all; #if NR_CPUS == 1 -#define nr_cpu_ids 1 #define first_cpu(src) ({ (void)(src); 0; }) #define next_cpu(n, src) ({ (void)(src); 1; }) #define cpumask_next_and(n, srcp, andp) ({ (void)(srcp), (void)(andp); 1; }) @@ -447,7 +454,6 @@ extern cpumask_t cpu_mask_all; #else /* NR_CPUS > 1 */ -extern int nr_cpu_ids; int __first_cpu(const cpumask_t *srcp); int __next_cpu(int n, const cpumask_t *srcp); int cpumask_next_and(int n, const cpumask_t *srcp, const cpumask_t *andp); --- test-compile.orig/init/main.c +++ test-compile/init/main.c @@ -373,6 +373,8 @@ EXPORT_SYMBOL(cpu_mask_all); #endif /* Setup number of possible processor ids */ +/* nr_cpu_ids is a real variable for large NR_CPUS. */ +#ifndef nr_cpu_ids int nr_cpu_ids __read_mostly = NR_CPUS; EXPORT_SYMBOL(nr_cpu_ids); @@ -386,6 +388,11 @@ void __init setup_nr_cpu_ids(void) nr_cpu_ids = highest_cpu + 1; } +#else +void __init setup_nr_cpu_ids(void) +{ +} +#endif /* ... nr_cpu_ids is a constant. */ #ifndef CONFIG_HAVE_SETUP_PER_CPU_AREA unsigned long __per_cpu_offset[NR_CPUS] __read_mostly; --