- panic if there's no runnable process

- more basic sanity check before recursive enter check (data segment)
 - try to jump to boot monitor instantly on recursive panic

kernel/arch/i386/system.c

@@ -20,6 +20,11 @@
 
 FORWARD _PROTOTYPE( void ser_debug, (int c));
 
+PUBLIC void arch_monitor(void)
+{
+	level0(monitor);
+}
+
 PUBLIC void arch_shutdown(int how)
 {
 	/* Mask all interrupts, including the clock. */
@@ -68,7 +73,7 @@ PUBLIC void arch_shutdown(int how)
 
 			arch_set_params(mybuffer, strlen(mybuffer)+1);
 		}
-		level0(monitor);
+		arch_monitor();
 	} else {
 		/* Reset the system by forcing a processor shutdown. First stop
 		 * the BIOS memory test by setting a soft reset flag.

kernel/debug.h

@@ -45,6 +45,9 @@
 	static int varname = 0;	\
 	int mustunlock = 0; \
 	if(!intr_disabled()) { lock; mustunlock = 1; } \
+	if(magictest != MAGICTEST) {	\
+		minix_panic(#varname " magictest failed", __LINE__); \
+	}	\
 	if(varname) {	\
 		minix_panic(#varname " recursive enter", __LINE__); \
 	} \

kernel/glo.h

@@ -58,6 +58,8 @@ EXTERN time_t boottime;
 EXTERN char params_buffer[512];		/* boot monitor parameters */
 EXTERN int minix_panicing;
 EXTERN int locklevel;
+#define MAGICTEST 0xC0FFEE23
+EXTERN u32_t magictest;			/* global magic number */
 
 #if DEBUG_TRACE
 EXTERN int verboseflags;

kernel/main.c

@@ -40,6 +40,9 @@ PUBLIC void main()
 
    /* Architecture-dependent initialization. */
    arch_init();
+
+   /* Global value to test segment sanity. */
+   magictest = MAGICTEST;
  
   /* Clear the process table. Anounce each slot as empty and set up mappings 
    * for proc_addr() and proc_nr() macros. Do the same for the table with 

kernel/proc.c

@@ -1327,6 +1327,7 @@ PRIVATE void pick_proc()
 		bill_ptr = rp;		/* bill for system time */
 	NOREC_RETURN(pick, );
   }
+  minix_panic("no runnable processes", NO_NUM);
 }
 
 /*===========================================================================*

kernel/proto.h

@@ -149,6 +149,7 @@ _PROTOTYPE( void idle_task, (void)                                     );
 _PROTOTYPE( void arch_init, (void)                                     );
 _PROTOTYPE( void ser_putc, (char)						);
 _PROTOTYPE( void arch_shutdown, (int)					);
+_PROTOTYPE( void arch_monitor, (void)					);
 _PROTOTYPE( void arch_get_aout_headers, (int i, struct exec *h)		);
 _PROTOTYPE( void restart, (void)                                        );
 _PROTOTYPE( void read_tsc, (unsigned long *high, unsigned long *low)    );

kernel/utility.c

@@ -37,7 +37,9 @@ char *mess;
 int nr;
 {
 /* The system has run aground of a fatal kernel error. Terminate execution. */
-if (!minix_panicing++) {
+if (minix_panicing++) {
+	arch_monitor();
+}
 
   if (mess != NULL) {
 	kprintf("kernel panic: %s", mess);
@@ -48,7 +50,6 @@ if (!minix_panicing++) {
 
   kprintf("kernel: ");
   util_stacktrace();
-}
 
   /* Abort MINIX. */
   minix_shutdown(NULL);