diff options
Diffstat (limited to 'lib/percpu_counter.c')
| -rw-r--r-- | lib/percpu_counter.c | 37 |
1 files changed, 14 insertions, 23 deletions
diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c index dba56c5c1837..5004463c4f9f 100644 --- a/lib/percpu_counter.c +++ b/lib/percpu_counter.c @@ -122,8 +122,19 @@ void percpu_counter_sync(struct percpu_counter *fbc) } EXPORT_SYMBOL(percpu_counter_sync); -static s64 __percpu_counter_sum_mask(struct percpu_counter *fbc, - const struct cpumask *cpu_mask) +/* + * Add up all the per-cpu counts, return the result. This is a more accurate + * but much slower version of percpu_counter_read_positive(). + * + * We use the cpu mask of (cpu_online_mask | cpu_dying_mask) to capture sums + * from CPUs that are in the process of being taken offline. Dying cpus have + * been removed from the online mask, but may not have had the hotplug dead + * notifier called to fold the percpu count back into the global counter sum. + * By including dying CPUs in the iteration mask, we avoid this race condition + * so __percpu_counter_sum() just does the right thing when CPUs are being taken + * offline. + */ +s64 __percpu_counter_sum(struct percpu_counter *fbc) { s64 ret; int cpu; @@ -131,35 +142,15 @@ static s64 __percpu_counter_sum_mask(struct percpu_counter *fbc, raw_spin_lock_irqsave(&fbc->lock, flags); ret = fbc->count; - for_each_cpu(cpu, cpu_mask) { + for_each_cpu_or(cpu, cpu_online_mask, cpu_dying_mask) { s32 *pcount = per_cpu_ptr(fbc->counters, cpu); ret += *pcount; } raw_spin_unlock_irqrestore(&fbc->lock, flags); return ret; } - -/* - * Add up all the per-cpu counts, return the result. This is a more accurate - * but much slower version of percpu_counter_read_positive() - */ -s64 __percpu_counter_sum(struct percpu_counter *fbc) -{ - return __percpu_counter_sum_mask(fbc, cpu_online_mask); -} EXPORT_SYMBOL(__percpu_counter_sum); -/* - * This is slower version of percpu_counter_sum as it traverses all possible - * cpus. Use this only in the cases where accurate data is needed in the - * presense of CPUs getting offlined. - */ -s64 percpu_counter_sum_all(struct percpu_counter *fbc) -{ - return __percpu_counter_sum_mask(fbc, cpu_possible_mask); -} -EXPORT_SYMBOL(percpu_counter_sum_all); - int __percpu_counter_init(struct percpu_counter *fbc, s64 amount, gfp_t gfp, struct lock_class_key *key) { |