+ /* If the IRQ handler (which runs lockless) needs to be
+ * quiesced, the following bitmask state is used. The
+ * SYNC flag is set by non-IRQ context code to initiate
+ * the quiescence.
+ *
+ * When the IRQ handler notices that SYNC is set, it
+ * disables interrupts and returns.
+ *
+ * When all outstanding IRQ handlers have returned after
+ * the SYNC flag has been set, the setter can be assured
+ * that interrupts will no longer get run.
+ *
+ * In this way all SMP driver locks are never acquired
+ * in hw IRQ context, only sw IRQ context or lower.
+ */
+ unsigned int irq_sync;
+