From c71458d20f17ef747cb314f2526701454e35335a Mon Sep 17 00:00:00 2001
From: Sathya Narayanan <sramamir@eng.ucsd.edu>
Date: Sun, 31 Jan 2016 21:31:51 -0800
Subject: [PATCH] Context switch working

---
 osproject_cswitch.c | 68 ++++++++++++++++++++++-------------------------------
 1 file changed, 28 insertions(+), 40 deletions(-)

diff --git a/osproject_cswitch.c b/osproject_cswitch.c
index 2bcdf62..33df7e3 100644
--- a/osproject_cswitch.c
+++ b/osproject_cswitch.c
@@ -19,62 +19,50 @@
  * express or implied warranty.
  */
 
-#ifndef lint
-static char rcsid[] = "$Header: /sprite/src/benchmarks/cswitch/RCS/cswitch.c,v 1.1 89/08/31 13:19:37 ouster Exp $ SPRITE (Berkeley)";
-#endif not lint
-
 #include <stdio.h>
-#include <sys/time.h>
-
-main(argc,argv)
-    int argc;
-    char **argv;
+int main(int argc, char **argv)
 {
     int count, i, toSlave[2], fromSlave[2];
     int pid;
     char buffer[10];
-    struct timeval begin ,end;
-    int micros;
+    unsigned int begin ,end;
     double timePer;
-    extern int errno;
+	unsigned int regr;
+   	asm volatile("mrc p15, 0, %0, c9, c14, 0" : "=r" (regr));
+	printf("regr: %x\n", regr);
 
-    if (argc != 2 ) {
-	fprintf(stderr, "Ping takes one argument: count.\n");
-	return;
-    }
-    count = 0;
-    sscanf(argv[1], "%d", &count);
+	count = 10;
     pipe(toSlave);
     pipe(fromSlave);
     pid = fork();
-    if (pid == 0) {
-	write(fromSlave[1], "a", 1);
-	while (1) {
-	    read(toSlave[0], buffer, 1);
-	    if (buffer[0] != 'a') {
-		exit(0);
-	    }
-	    write(fromSlave[1], "a", 1);
-	}
-    }
-    if (pid == -1) {
-	fprintf(stderr, "Couldn't fork slave process: error %d.\n",
-		errno);
-	return;
+	if (pid == 0) {
+		write(fromSlave[1], "a", 1);
+		while (1) {
+			read(toSlave[0], buffer, 1);
+			asm volatile("mrc p15, 0, %0, c9, c13, 0" : "=r" (end));
+			if (buffer[0] != 'a') {
+				printf("Exiting\n");
+				return -1;
+			}
+	    	//write(fromSlave[1], "a", 1);
+			printf("end: %u\n", end);
+		}
     }
+	if (pid == -1) {
+		printf("Couldn't fork slave process: error %d.\n");
+		return;
+	}
     read(fromSlave[0], buffer, 1);
-    gettimeofday(&begin, (struct timezone *) NULL);
     for (i = 0; i < count; i++) {
-	write(toSlave[1], "a", 1);
-	read(fromSlave[0], buffer, 1);
+		asm volatile("mrc p15, 0, %0, c9, c13, 0" : "=r" (begin));
+		write(toSlave[1], "a", 1);
+		//read(fromSlave[0], buffer, 1);
+		usleep(10000);
+		printf("Start: %u\n", begin);
     }
-    gettimeofday(&end, (struct timezone *) NULL);
-    micros = 1000000*(end.tv_sec - begin.tv_sec)
-	    + end.tv_usec - begin.tv_usec;
     write(toSlave[1], "b", 1);
-    timePer = micros;
-    timePer /= count * 1000;
 
+	timePer = (end - begin)/count;
     printf("Elapsed time per ping (2 context switches): %.2f milliseconds.\n",
 	    timePer);
 }
-- 
1.9.1