+
+/**
+ * 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)
+ */
+int lprocfs_stats_lock(struct lprocfs_stats *stats,
+ enum lprocfs_stats_lock_ops opc,
+ unsigned long *flags)
+{
+ if (stats->ls_flags & LPROCFS_STATS_FLAG_NOPERCPU) {
+ if (stats->ls_flags & LPROCFS_STATS_FLAG_IRQ_SAFE)
+ spin_lock_irqsave(&stats->ls_lock, *flags);
+ else
+ spin_lock(&stats->ls_lock);
+ return opc == LPROCFS_GET_NUM_CPU ? 1 : 0;
+ }
+
+ switch (opc) {
+ case LPROCFS_GET_SMP_ID: {
+ unsigned int cpuid = get_cpu();
+
+ if (unlikely(!stats->ls_percpu[cpuid])) {
+ int rc = lprocfs_stats_alloc_one(stats, cpuid);
+
+ if (rc < 0) {
+ put_cpu();
+ return rc;
+ }
+ }
+ return cpuid;
+ }
+ case LPROCFS_GET_NUM_CPU:
+ return stats->ls_biggest_alloc_num;
+ default:
+ LBUG();
+ }
+}
+
+/**
+ * Unlock statistics structure after access.
+ *
+ * Unlock the lock acquired via lprocfs_stats_lock() for global statistics,
+ * or unpin this thread from the current cpuid for per-CPU statistics.
+ *
+ * This function must be called using the same arguments as used when calling
+ * lprocfs_stats_lock() so that the correct operation can be performed.
+ *
+ * \param[in] stats statistics structure to unlock
+ * \param[in] opc type of operation (current cpuid or number of structs)
+ * \param[in] flags CPU interrupt saved state for IRQ-safe locking
+ */
+void lprocfs_stats_unlock(struct lprocfs_stats *stats,
+ enum lprocfs_stats_lock_ops opc,
+ unsigned long *flags)
+{
+ if (stats->ls_flags & LPROCFS_STATS_FLAG_NOPERCPU) {
+ if (stats->ls_flags & LPROCFS_STATS_FLAG_IRQ_SAFE)
+ spin_unlock_irqrestore(&stats->ls_lock, *flags);
+ else
+ spin_unlock(&stats->ls_lock);
+ } else if (opc == LPROCFS_GET_SMP_ID) {
+ put_cpu();
+ }
+}
+
+/** add up per-cpu counters */