From 75b0c6fc91c1264aaa5d080d9faeb87c90d02ad3 Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@csail.mit.edu>
Date: Fri, 5 Jul 2019 12:33:26 -0400
Subject: [PATCH] back-port fork/exit/exit tests to xv6-riscv

---
 user/cow.c       |   2 +-
 user/init.c      |   5 ++-
 user/usertests.c | 113 ++++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 115 insertions(+), 5 deletions(-)

diff --git a/user/cow.c b/user/cow.c
index 45efc98..0426600 100644
--- a/user/cow.c
+++ b/user/cow.c
@@ -129,7 +129,7 @@ filetest()
 {
   int parent = getpid();
   
-  printf(1, "file test: ");
+  printf(1, "file: ");
   
   buf[0] = 99;
 
diff --git a/user/init.c b/user/init.c
index f36ba31..03e60da 100644
--- a/user/init.c
+++ b/user/init.c
@@ -31,7 +31,8 @@ main(void)
       printf(1, "init: exec sh failed\n");
       exit();
     }
-    while((wpid=wait()) >= 0 && wpid != pid)
-      printf(1, "zombie!\n");
+    while((wpid=wait()) >= 0 && wpid != pid){
+      //printf(1, "zombie!\n");
+    }
   }
 }
diff --git a/user/usertests.c b/user/usertests.c
index ef70bfb..9d46b1a 100644
--- a/user/usertests.c
+++ b/user/usertests.c
@@ -417,16 +417,18 @@ exitwait(void)
 {
   int i, pid;
 
+  printf(1, "exitwait test\n");
+
   for(i = 0; i < 100; i++){
     pid = fork();
     if(pid < 0){
       printf(1, "fork failed\n");
-      return;
+      exit();
     }
     if(pid){
       if(wait() != pid){
         printf(1, "wait wrong pid\n");
-        return;
+        exit();
       }
     } else {
       exit();
@@ -435,6 +437,109 @@ exitwait(void)
   printf(1, "exitwait ok\n");
 }
 
+// try to find races in the reparenting
+// code that handles a parent exiting
+// when it still has live children.
+void
+reparent(void)
+{
+  int master_pid = getpid();
+  
+  printf(1, "reparent test\n");
+
+  for(int i = 0; i < 100; i++){
+    int pid = fork();
+    if(pid < 0){
+      printf(1, "fork failed\n");
+      exit();
+    }
+    if(pid){
+      if(wait() != pid){
+        printf(1, "wait wrong pid\n");
+        exit();
+      }
+    } else {
+      int pid2 = fork();
+      if(pid2 < 0){
+        printf(1, "fork failed\n");
+        kill(master_pid);
+        exit();
+      }
+      if(pid2 == 0){
+        exit();
+      } else {
+        exit();
+      }
+    }
+  }
+  printf(1, "reparent ok\n");
+}
+
+// what if two children exit() at the same time?
+void
+twochildren(void)
+{
+  printf(1, "twochildren test\n");
+
+  for(int i = 0; i < 1000; i++){
+    int pid1 = fork();
+    if(pid1 < 0){
+      printf(1, "fork failed\n");
+      exit();
+    }
+    if(pid1 == 0){
+      exit();
+    } else {
+      int pid2 = fork();
+      if(pid2 < 0){
+        printf(1, "fork failed\n");
+        exit();
+      }
+      if(pid2 == 0){
+        exit();
+      } else {
+        wait();
+        wait();
+      }
+    }
+  }
+  printf(1, "twochildren ok\n");
+}
+
+void
+forkforkfork(void)
+{
+  printf(1, "forkforkfork test\n");
+
+  unlink("stopforking");
+
+  int pid = fork();
+  if(pid < 0){
+    printf(1, "fork failed");
+    exit();
+  }
+  if(pid == 0){
+    while(1){
+      int fd = open("stopforking", 0);
+      if(fd >= 0){
+        exit();
+      }
+      if(fork() < 0){
+        close(open("stopforking", O_CREATE|O_RDWR));
+      }
+    }
+
+    exit();
+  }
+
+  sleep(2);
+  close(open("stopforking", O_CREATE|O_RDWR));
+  wait();
+  sleep(1);
+
+  printf(1, "forkforkfork ok\n");
+}
+
 void
 mem(void)
 {
@@ -1751,6 +1856,10 @@ main(int argc, char *argv[])
   }
   close(open("usertests.ran", O_CREATE));
 
+  reparent();
+  twochildren();
+  forkforkfork();
+  
   argptest();
   createdelete();
   linkunlink();