vt: try and do something sane about vt and irq handling

diff --git a/Kernel/vt.c b/Kernel/vt.c
index 2c6eb0b..041793d 100644 (file)
--- a/Kernel/vt.c
+++ b/Kernel/vt.c
@@ -60,6 +60,8 @@ uint8_t vtattr;
 static signed char cursorx;
 static signed char cursory = VT_INITIAL_LINE;
 static signed char ncursory;
+static uint8_t vtpend;
+static uint8_t vtbusy;
 
 static void cursor_fix(void)
 {
@@ -175,35 +177,65 @@ static int escout(unsigned char c)
 /* VT52 alike functionality */
 void vtoutput(unsigned char *p, unsigned int len)
 {
+       irqflags_t irq;
+       uint8_t cq;
+
+       /* We can get re-entry into the vt code from tty echo. This is one of
+          the few places in Fuzix interrupts bite us this way.
+
+          If we have a clash then we queue the echoed symbol and print it
+          in the thread of execution it interrupted. We only queue one so
+          in theory might lose the odd echo - but the same occurs with real
+          uarts. If anyone actually has printing code slow enough this is a
+          problem then vtpend can turn into a small queue */
+       irq = di();
+       if (vtbusy) {
+               vtpend = *p;
+               irqrestore(irq);
+               return;
+       }
+       vtbusy = 1;
+       irqrestore(irq);
        cursor_off();
-       while (len--) {
-               unsigned char c = *p++;
-               if (vtmode == 0) {
-                       charout(c);
-                       continue;
+       do {
+               while (len--) {
+                       unsigned char c = *p++;
+                       if (vtmode == 0) {
+                               charout(c);
+                               continue;
+                       }
+                       if (vtmode == 1) {
+                               vtmode = escout(c);
+                               continue;
+                       }
+                       if (vtmode == 2) {
+                               ncursory = c - ' ';
+                               vtmode++;
+                               continue;
+                       } else if (vtmode == 3) {
+                               int ncursorx = c - ' ';
+                               if (ncursory >= 0 && ncursorx <= VT_BOTTOM)
+                                       cursory = ncursory;
+                               if (ncursorx >= 0 && ncursorx <= VT_RIGHT)
+                                       cursorx = ncursorx;
+                                       vtmode = 0;
+                       } else {
+                               vtattr = c;
+                               vtmode = 0;
+                               continue;
+                       }
                }
-               if (vtmode == 1) {
-                       vtmode = escout(c);
-                       continue;
-               }
-               if (vtmode == 2) {
-                       ncursory = c - ' ';
-                       vtmode++;
-                       continue;
-               } else if (vtmode == 3) {
-                       int ncursorx = c - ' ';
-                       if (ncursory >= 0 && ncursorx <= VT_BOTTOM)
-                               cursory = ncursory;
-                       if (ncursorx >= 0 && ncursorx <= VT_RIGHT)
-                               cursorx = ncursorx;
-                       vtmode = 0;
-               } else {
-                       vtattr = c;
-                       vtmode = 0;
-                       continue;
-               }
-       }
+               /* Copy the pending symbol and clear the buffer */
+               cq = vtpend;
+               vtpend = 0;
+               /* Any loops print the single byte in cq */
+               p = &cq;
+               len = 1;
+               /* Until we don't get interrupted */
+       } while(cq);
+
        cursor_on(cursory, cursorx);
+       vtbusy = 0;
 }
 
 int vt_ioctl(uint8_t minor, uarg_t request, char *data)