From 490f91ab53e22d90afb1ee37d5148e341ccf538e Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@csail.mit.edu>
Date: Fri, 28 Aug 2020 05:51:48 -0400
Subject: [PATCH] move panicked check to uart.c

---
 kernel/console.c | 13 -------------
 kernel/printf.c  |  2 +-
 kernel/uart.c    | 13 +++++++++++++
 user/grind.c     | 20 ++++++++++++++++++--
 4 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/kernel/console.c b/kernel/console.c
index 1885593..d606ed2 100644
--- a/kernel/console.c
+++ b/kernel/console.c
@@ -33,13 +33,6 @@
 void
 consputc(int c)
 {
-  extern volatile int panicked; // from printf.c
-
-  if(panicked){
-    for(;;)
-      ;
-  }
-
   if(c == BACKSPACE){
     // if the user typed backspace, overwrite with a space.
     uartputc_sync('\b'); uartputc_sync(' '); uartputc_sync('\b');
@@ -66,12 +59,6 @@ int
 consolewrite(int user_src, uint64 src, int n)
 {
   int i;
-  extern volatile int panicked; // from printf.c
-
-  if(panicked){
-    for(;;)
-      ;
-  }
 
   acquire(&cons.lock);
   for(i = 0; i < n; i++){
diff --git a/kernel/printf.c b/kernel/printf.c
index 1a83284..e1347de 100644
--- a/kernel/printf.c
+++ b/kernel/printf.c
@@ -121,7 +121,7 @@ panic(char *s)
   printf("panic: ");
   printf(s);
   printf("\n");
-  panicked = 1; // freeze output from other CPUs
+  panicked = 1; // freeze uart output from other CPUs
   for(;;)
     ;
 }
diff --git a/kernel/uart.c b/kernel/uart.c
index daf9f04..ce89615 100644
--- a/kernel/uart.c
+++ b/kernel/uart.c
@@ -45,6 +45,8 @@ char uart_tx_buf[UART_TX_BUF_SIZE];
 int uart_tx_w; // write next to uart_tx_buf[uart_tx_w++]
 int uart_tx_r; // read next from uart_tx_buf[uar_tx_r++]
 
+extern volatile int panicked; // from printf.c
+
 void uartstart();
 
 void
@@ -85,6 +87,12 @@ void
 uartputc(int c)
 {
   acquire(&uart_tx_lock);
+
+  if(panicked){
+    for(;;)
+      ;
+  }
+
   while(1){
     if(((uart_tx_w + 1) % UART_TX_BUF_SIZE) == uart_tx_r){
       // buffer is full.
@@ -109,6 +117,11 @@ uartputc_sync(int c)
 {
   push_off();
 
+  if(panicked){
+    for(;;)
+      ;
+  }
+
   // wait for Transmit Holding Empty to be set in LSR.
   while((ReadReg(LSR) & LSR_TX_IDLE) == 0)
     ;
diff --git a/user/grind.c b/user/grind.c
index 14e2aae..d11b20b 100644
--- a/user/grind.c
+++ b/user/grind.c
@@ -292,8 +292,8 @@ go(int which_child)
   }
 }
 
-int
-main()
+void
+iter()
 {
   unlink("a");
   unlink("b");
@@ -331,3 +331,19 @@ main()
 
   exit(0);
 }
+
+int
+main()
+{
+  while(1){
+    int pid = fork();
+    if(pid == 0){
+      iter();
+      exit(0);
+    }
+    if(pid > 0){
+      wait(0);
+    }
+    sleep(20);
+  }
+}