From e54b0e132b0f1ec6529812f6852b8b61422cd88d Mon Sep 17 00:00:00 2001
From: Stefan Lankes <lankes@lfbs.rwth-aachen.de>
Date: Fri, 21 Oct 2011 14:21:39 -0700
Subject: [PATCH] add test and set barrier

---
 arch/x86/include/asm/RCCE.h |  1 +
 arch/x86/scc/RCCE_admin.c   | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/arch/x86/include/asm/RCCE.h b/arch/x86/include/asm/RCCE.h
index 128ba664..d88e5723 100644
--- a/arch/x86/include/asm/RCCE.h
+++ b/arch/x86/include/asm/RCCE.h
@@ -190,6 +190,7 @@ int    RCCE_comm_size(RCCE_COMM, int *);
 int    RCCE_comm_rank(RCCE_COMM, int *);
 void   RCCE_fence(void);
 int    RCCE_barrier(RCCE_COMM *);
+int    RCCE_TNS_barrier(RCCE_COMM* comm); 
 int    RCCE_error_string(int, char *, int *);
 int    RCCE_debug_set(int);
 int    RCCE_debug_unset(int);
diff --git a/arch/x86/scc/RCCE_admin.c b/arch/x86/scc/RCCE_admin.c
index 78b26b21..09e70166 100644
--- a/arch/x86/scc/RCCE_admin.c
+++ b/arch/x86/scc/RCCE_admin.c
@@ -48,6 +48,8 @@
 // En-/ or disable debug prints...
 #define DEBUG 0
 
+#define Test_and_Set(a) ((*(virtual_lockaddress[a])) & 0x01)
+
 //......................................................................................
 // GLOBAL VARIABLES USED BY THE LIBRARY
 //......................................................................................
@@ -105,6 +107,38 @@ void RC_cache_invalidate() {
   return;
 }
 
+int RCCE_TNS_barrier(RCCE_COMM* comm) {
+
+// two roundtrips to realize a barrier using a T&S Register for each core.
+
+// 1. search first free T&S Register to spin
+// 2. last waiter wakes up first waiter and continues local wait
+// 3. first waiter wakes up second waiter by releasing its lock ...
+// At least every used T&S Register is 0 and no UE can overtake a barrier.
+
+ int num = comm->size;
+ int step = 0;
+ //fprintf(stderr,"%d:\t enter barrier \n",id);
+
+ while( !Test_and_Set(step) ) ++step;
+ // only one UE runs until T&S # num-1
+
+ //fprintf(stderr,"%d:\t step %d\n",id,step);
+
+ if(step == num-1) {
+   //fprintf(stderr,"%d:\t I am the last one\n",id);
+   *(virtual_lockaddress[0]) = 0x0;
+   while(!Test_and_Set(step)) ;
+   *(virtual_lockaddress[step]) = 0x0;
+ } else {
+   while(!Test_and_Set(step)) ;
+   *(virtual_lockaddress[step]) = 0x0;
+   *(virtual_lockaddress[step+1]) = 0x0;
+ }
+ //fprintf(stderr,"released barrier! step: %d\n", step);
+ return RCCE_SUCCESS;
+}
+
 //--------------------------------------------------------------------------------------
 // FUNCTION: RC_COMM_BUFFER_SIZE
 //--------------------------------------------------------------------------------------