+/*
+ * Simple lockless ring to communicate PFNs from the exception handler with the
+ * process context work function. This is vastly simplified because there's
+ * only a single reader and a single writer.
+ */
+#define MCE_RING_SIZE 16 /* we use one entry less */
+
+struct mce_ring {
+ unsigned short start;
+ unsigned short end;
+ unsigned long ring[MCE_RING_SIZE];
+};
+static DEFINE_PER_CPU(struct mce_ring, mce_ring);
+
+/* Runs with CPU affinity in workqueue */
+static int mce_ring_empty(void)
+{
+ struct mce_ring *r = &__get_cpu_var(mce_ring);
+
+ return r->start == r->end;
+}
+
+static int mce_ring_get(unsigned long *pfn)
+{
+ struct mce_ring *r;
+ int ret = 0;
+
+ *pfn = 0;
+ get_cpu();
+ r = &__get_cpu_var(mce_ring);
+ if (r->start == r->end)
+ goto out;
+ *pfn = r->ring[r->start];
+ r->start = (r->start + 1) % MCE_RING_SIZE;
+ ret = 1;
+out:
+ put_cpu();
+ return ret;
+}
+
+/* Always runs in MCE context with preempt off */
+static int mce_ring_add(unsigned long pfn)
+{
+ struct mce_ring *r = &__get_cpu_var(mce_ring);
+ unsigned next;
+
+ next = (r->end + 1) % MCE_RING_SIZE;
+ if (next == r->start)
+ return -1;
+ r->ring[r->end] = pfn;
+ wmb();
+ r->end = next;
+ return 0;
+}
+