From 16b3b63f06c1ea17da484aeebea4a57fb2a6e44a Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@csail.mit.edu>
Date: Wed, 6 Nov 2019 11:18:43 -0500
Subject: [PATCH] grind: run parallel system calls forever

---
 Makefile         |   1 +
 user/grind.c     | 160 +++++++++++++++++++++++++++++++++++++++++++++++
 user/usertests.c |  14 +++--
 3 files changed, 170 insertions(+), 5 deletions(-)
 create mode 100644 user/grind.c

diff --git a/Makefile b/Makefile
index 7229d5e..46fd956 100644
--- a/Makefile
+++ b/Makefile
@@ -127,6 +127,7 @@ UPROGS=\
 	$U/_sh\
 	$U/_stressfs\
 	$U/_usertests\
+	$U/_grind\
 	$U/_wc\
 	$U/_zombie\
 
diff --git a/user/grind.c b/user/grind.c
new file mode 100644
index 0000000..97a8a93
--- /dev/null
+++ b/user/grind.c
@@ -0,0 +1,160 @@
+//
+// run random system calls in parallel forever.
+//
+
+#include "kernel/param.h"
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+#include "kernel/fs.h"
+#include "kernel/fcntl.h"
+#include "kernel/syscall.h"
+#include "kernel/memlayout.h"
+#include "kernel/riscv.h"
+
+// from FreeBSD.
+int
+do_rand(unsigned long *ctx)
+{
+/*
+ * Compute x = (7^5 * x) mod (2^31 - 1)
+ * without overflowing 31 bits:
+ *      (2^31 - 1) = 127773 * (7^5) + 2836
+ * From "Random number generators: good ones are hard to find",
+ * Park and Miller, Communications of the ACM, vol. 31, no. 10,
+ * October 1988, p. 1195.
+ */
+    long hi, lo, x;
+
+    /* Transform to [1, 0x7ffffffe] range. */
+    x = (*ctx % 0x7ffffffe) + 1;
+    hi = x / 127773;
+    lo = x % 127773;
+    x = 16807 * lo - 2836 * hi;
+    if (x < 0)
+        x += 0x7fffffff;
+    /* Transform to [0, 0x7ffffffd] range. */
+    x--;
+    *ctx = x;
+    return (x);
+}
+
+unsigned long rand_next = 1;
+
+int
+rand(void)
+{
+    return (do_rand(&rand_next));
+}
+
+void
+go()
+{
+  int fd = -1;
+  static char buf[999];
+  char *break0 = sbrk(0);
+  
+  while(1){
+    int what = rand() % 20;
+    if(what == 1){
+      close(open("a", O_CREATE|O_RDWR));
+    } else if(what == 2){
+      close(open("b", O_CREATE|O_RDWR));
+    } else if(what == 3){
+      unlink("a");
+    } else if(what == 4){
+      unlink("b");
+    } else if(what == 5){
+      close(fd);
+      fd = open("a", O_CREATE|O_RDWR);
+    } else if(what == 6){
+      close(fd);
+      fd = open("b", O_CREATE|O_RDWR);
+    } else if(what == 7){
+      write(fd, buf, sizeof(buf));
+    } else if(what == 8){
+      read(fd, buf, sizeof(buf));
+    } else if(what == 9){
+      mkdir("a");
+    } else if(what == 10){
+      mkdir("b");
+    } else if(what == 11){
+      unlink("b");
+      link("a", "b");
+    } else if(what == 12){
+      unlink("a");
+      link("b", "a");
+    } else if(what == 13){
+      int pid = fork();
+      if(pid == 0){
+        exit(0);
+      }
+      wait(0);
+    } else if(what == 14){
+      int pid = fork();
+      if(pid == 0){
+        fork();
+        fork();
+        exit(0);
+      }
+      wait(0);
+    } else if(what == 15){
+      sbrk(6011);
+    } else if(what == 16){
+      if(sbrk(0) > break0)
+        sbrk(-(sbrk(0) - break0));
+    } else if(what == 17){
+      int pid = fork();
+      if(pid == 0){
+        close(open("a", O_CREATE|O_RDWR));
+        exit(0);
+      }
+      kill(pid);
+      wait(0);
+    } else if(what == 18){
+      int pid = fork();
+      if(pid == 0){
+        kill(getpid());
+        exit(0);
+      }
+      wait(0);
+    }
+  }
+}
+
+int
+main()
+{
+  int pid1 = fork();
+  if(pid1 < 0){
+    printf("grind: fork failed\n");
+    exit(1);
+  }
+  if(pid1 == 0){
+    rand_next = 31;
+    go();
+    exit(0);
+  }
+
+  int pid2 = fork();
+  if(pid2 < 0){
+    printf("grind: fork failed\n");
+    exit(1);
+  }
+  if(pid2 == 0){
+    rand_next = 7177;
+    go();
+    exit(0);
+  }
+
+  int st1 = -1;
+  wait(&st1);
+  if(st1 != 0){
+    kill(pid1);
+    kill(pid2);
+  }
+  int st2 = -1;
+  wait(&st2);
+
+  exit(0);
+}
diff --git a/user/usertests.c b/user/usertests.c
index 8d1d06a..9aa0ed4 100644
--- a/user/usertests.c
+++ b/user/usertests.c
@@ -1038,11 +1038,15 @@ concreate(char *s)
       close(open(file, 0));
       close(open(file, 0));
       close(open(file, 0));
+      close(open(file, 0));
+      close(open(file, 0));
     } else {
       unlink(file);
       unlink(file);
       unlink(file);
       unlink(file);
+      unlink(file);
+      unlink(file);
     }
     if(pid == 0)
       exit(0);
@@ -1106,7 +1110,7 @@ bigdir(char *s)
     name[2] = '0' + (i % 64);
     name[3] = '\0';
     if(link("bd", name) != 0){
-      printf("%s: bigdir link failed\n", s);
+      printf("%s: bigdir link(bd, %s) failed\n", s, name);
       exit(1);
     }
   }
@@ -1335,8 +1339,8 @@ bigfile(char *s)
   enum { N = 20, SZ=600 };
   int fd, i, total, cc;
 
-  unlink("bigfile");
-  fd = open("bigfile", O_CREATE | O_RDWR);
+  unlink("bigfile.dat");
+  fd = open("bigfile.dat", O_CREATE | O_RDWR);
   if(fd < 0){
     printf("%s: cannot create bigfile", s);
     exit(1);
@@ -1350,7 +1354,7 @@ bigfile(char *s)
   }
   close(fd);
 
-  fd = open("bigfile", 0);
+  fd = open("bigfile.dat", 0);
   if(fd < 0){
     printf("%s: cannot open bigfile\n", s);
     exit(1);
@@ -1379,7 +1383,7 @@ bigfile(char *s)
     printf("%s: read bigfile wrong total\n", s);
     exit(1);
   }
-  unlink("bigfile");
+  unlink("bigfile.dat");
 }
 
 void