+ unsigned int cpuid);
+
+/**
+ * Lock statistics structure for access, possibly only on this CPU.
+ *
+ * The statistics struct may be allocated with per-CPU structures for
+ * efficient concurrent update (usually only on server-wide stats), or
+ * as a single global struct (e.g. for per-client or per-job statistics),
+ * so the required locking depends on the type of structure allocated.
+ *
+ * For per-CPU statistics, pin the thread to the current cpuid so that
+ * will only access the statistics for that CPU. If the stats structure
+ * for the current CPU has not been allocated (or previously freed),
+ * allocate it now. The per-CPU statistics do not need locking since
+ * the thread is pinned to the CPU during update.
+ *
+ * For global statistics, lock the stats structure to prevent concurrent update.
+ *
+ * \param[in] stats statistics structure to lock
+ * \param[in] opc type of operation:
+ * LPROCFS_GET_SMP_ID: "lock" and return current CPU index
+ * for incrementing statistics for that CPU
+ * LPROCFS_GET_NUM_CPU: "lock" and return number of used
+ * CPU indices to iterate over all indices
+ * \param[out] flags CPU interrupt saved state for IRQ-safe locking
+ *
+ * \retval cpuid of current thread or number of allocated structs
+ * \retval negative on error (only for opc LPROCFS_GET_SMP_ID + per-CPU stats)