From: Rusty Russell Subject: cpumask: Use all NR_CPUS bits unless CONFIG_CPUMASK_OFFSTACK Impact: futureproof as we convert more code to new APIs The old cpumask operators treat all NR_CPUS bits as relevent, the new ones use nr_cpumask_bits. For large NR_CPUS and small nr_cpu_ids, this makes a difference. However, mixing the two can cause problems with undefined bits. An arch which sets CONFIG_CPUMASK_OFFSTACK should have converted across to the new operators, so it's safe in that case. (Thanks to Stephen Rothwell for bisecting the initial unused-bits bug, and Mike Travis for this solution). Signed-off-by: Rusty Russell Cc: Mike Travis --- include/linux/cpumask.h | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -510,9 +510,6 @@ extern cpumask_t cpu_active_map; [BITS_TO_LONGS(NR_CPUS)-1] = CPU_MASK_LAST_WORD \ } -/* This produces more efficient code. */ -#define nr_cpumask_bits NR_CPUS - #else /* NR_CPUS > BITS_PER_LONG */ #define CPU_BITS_ALL \ @@ -520,9 +517,15 @@ extern cpumask_t cpu_active_map; [0 ... BITS_TO_LONGS(NR_CPUS)-2] = ~0UL, \ [BITS_TO_LONGS(NR_CPUS)-1] = CPU_MASK_LAST_WORD \ } +#endif /* NR_CPUS > BITS_PER_LONG */ +#ifdef CONFIG_CPUMASK_OFFSTACK +/* Assuming NR_CPUS is huge, a runtime limit is more efficient. Also, + * not all bits may be allocated. */ #define nr_cpumask_bits nr_cpu_ids -#endif /* NR_CPUS > BITS_PER_LONG */ +#else +#define nr_cpumask_bits NR_CPUS +#endif /* verify cpu argument to cpumask_* operators */ static inline unsigned int cpumask_check(unsigned int cpu)