init commit of lab3_3

Makefile

@@ -70,7 +70,7 @@ USER_OBJS  		:= $(addprefix $(OBJ_DIR)/, $(patsubst %.c,%.o,$(USER_CPPS)))
 
 
 
-USER_TARGET 	:= $(OBJ_DIR)/app_yield
+USER_TARGET 	:= $(OBJ_DIR)/app_two_long_loops
 #------------------------targets------------------------
 $(OBJ_DIR):
 	@-mkdir -p $(OBJ_DIR)	

kernel/process.h

@@ -86,6 +86,9 @@ typedef struct process_t {
   struct process_t *parent;
   // next queue element
   struct process_t *queue_next;
+
+  // accounting. added @lab3_3
+  int tick_count;
 }process;
 
 // switch to run user app

kernel/strap.c

@@ -67,6 +67,18 @@ void handle_user_page_fault(uint64 mcause, uint64 sepc, uint64 stval) {
   }
 }
 
+//
+// implements round-robin scheduling. added @lab3_3
+//
+void rrsched() {
+  // TODO (lab3_3): implements round-robin scheduling.
+  // hint: increase the tick_count member of current process by one, if it is bigger than
+  // TIME_SLICE_LEN (means it has consumed its time slice), change its status into READY,
+  // place it in the rear of ready queue, and finally schedule next process to run.
+  panic( "You need to further implement the timer handling in lab3_3.\n" );
+
+}
+
 //
 // kernel/smode_trap.S will pass control to smode_trap_handler, when a trap happens
 // in S-mode.
@@ -91,6 +103,8 @@ void smode_trap_handler(void) {
       break;
     case CAUSE_MTIMER_S_TRAP:
       handle_mtimer_trap();
+      // invoke round-robin scheduler. added @lab3_3
+      rrsched();
       break;
     case CAUSE_STORE_PAGE_FAULT:
     case CAUSE_LOAD_PAGE_FAULT:

user/app_two_long_loops.c

@@ -1,6 +1,6 @@
 /*
- * The application of lab3_2.
- * parent and child processes intermittently give up their processors.
+ * The application of lab3_3.
+ * parent and child processes never give up their processor during execution.
  */
 
 #include "user/user_lib.h"
@@ -8,22 +8,18 @@
 
 int main(void) {
   uint64 pid = fork();
-  uint64 rounds = 0xffff;
+  uint64 rounds = 100000000;
+  uint64 interval = 10000000;
+  uint64 a = 0;
   if (pid == 0) {
     printu("Child: Hello world! \n");
     for (uint64 i = 0; i < rounds; ++i) {
-      if (i % 10000 == 0) {
-        printu("Child running %ld \n", i);
-        yield();
-      }
+      if (i % interval == 0) printu("Child running %ld \n", i);
     }
   } else {
     printu("Parent: Hello world! \n");
     for (uint64 i = 0; i < rounds; ++i) {
-      if (i % 10000 == 0) {
-        printu("Parent running %ld \n", i);
-        yield();
-      }
+      if (i % interval == 0) printu("Parent running %ld \n", i);
     }
   }