--- /dev/null
+/*
+ * This file is part of the Palacios Virtual Machine Monitor developed
+ * by the V3VEE Project with funding from the United States National
+ * Science Foundation and the Department of Energy.
+ *
+ * The V3VEE Project is a joint project between Northwestern University
+ * and the University of New Mexico. You can find out more at
+ * http://www.v3vee.org
+ *
+ * Copyright (c) 2015, Peter Dinda <pdinda@northwestern.edu>
+ * Copyright (c) 2015, The V3VEE Project <http://www.v3vee.org>
+ * All rights reserved.
+ *
+ * Author: Peter Dinda <pdinda@northwestern.edu>
+ *
+ * This is free software. You are permitted to use,
+ * redistribute, and modify it as specified in the file "V3VEE_LICENSE".
+ */
+
+#ifndef __VMM_SUBSET_H__
+#define __VMM_SUBSET_H__
+
+#ifdef __V3VEE__
+
+#include <palacios/vmm_types.h>
+
+/* Subset Barriers */
+
+typedef struct v3_counting_barrier {
+ // number of threads that must arrive at the barrier
+ // note that this can only be set when there is no barreir in progress
+ uint64_t size;
+ uint64_t count[2];
+ uint64_t cur;
+} v3_counting_barrier_t;
+
+
+static inline void v3_init_counting_barrier(v3_counting_barrier_t *b, uint64_t size)
+{
+ b->size=size; b->count[0]=b->count[1]=0; b->cur=0;
+}
+
+static inline void v3_counting_barrier(volatile v3_counting_barrier_t *b)
+{
+ uint64_t old;
+ volatile uint64_t *curp = &(b->cur);
+ long mycur = *curp;
+ volatile uint64_t *countp = &(b->count[mycur]);
+
+ old = __sync_fetch_and_add(countp,1);
+
+ if (old==(b->size-1)) {
+ // I'm the last to the party
+ *curp ^= 0x1;
+ *countp = 0;
+ } else {
+ // k1om compiler does not know what "volatile" means
+ // hence this hand-coding.
+ do {
+ __asm__ __volatile__( "movq %1, %0" : "=r"(old) : "m"(*countp) : );
+ } while (old);
+ }
+}
+
+
+#endif
+
+#endif
