Modify task_switch function so it can be used to switch to new tasks which have not...

diff --git a/kernel/arch/task.S b/kernel/arch/task.S
index a041b72dcdc605a0d367ccbe58faa3e23a0807b3..43f3b12fb4896f5fbf73313f980a0d7af3df6dfa 100644 (file)
--- a/kernel/arch/task.S
+++ b/kernel/arch/task.S
@@ -28,6 +28,7 @@
 #define OFFSET_CR3    4
 #define OFFSET_KSTACK 8
 #define OFFSET_PRIVL  12
+#define OFFSET_STATE  16
 
 .extern _cpu
 
@@ -219,7 +220,31 @@ task_switch:
        /* load new ESP */
 3:     movl    OFFSET_ESP0(%edi), %esp
 
-       /* pretend that we're returning from an interrupt */
+       /*
+        * If this is a new task, we have to use _int_restore to return,
+        * but if this task has been executed before, we can simply ret.
+        * New tasks have state TASK_STATE_NEW, which is zero.
+        */
+
+       movl    OFFSET_STATE(%edi), %eax
+       test    %eax, %eax
+       jz              4f
+       xorl    %eax, %eax
+
+       /*
+        * If the context has previously executed, it was interrupted in this
+        * very same function, so by switching back to its stack and page directory
+        * we have done enough to restore it's context. Everything else will happen
+        * when the task returns "naturally" to user-space
+        */
+       ret
+
+4:     movl    $1, OFFSET_STATE(%edi)
+       /*
+        * In the previous line, the task state is set to TASK_STATE_RUNNING.
+        * This is the only place where a transition from NEW to any other state
+        * should occur (excluding BROKEN)
+        */
        jmp             _int_restore
 
 task_get_current:

diff --git a/kernel/include/arch.h b/kernel/include/arch.h
index 7499bae28d4f79eceb158c14901cf6eb71bb1853..fec57bb59de89cfa1fb3670597a3621f59a9aa16 100644 (file)
--- a/kernel/include/arch.h
+++ b/kernel/include/arch.h
@@ -21,10 +21,11 @@
 
 #include <corax/types.h>
 
-#define TASK_STATE_BROKEN  0
+#define TASK_STATE_NEW     0
 #define TASK_STATE_RUNNING 1
 #define TASK_STATE_READY   2
 #define TASK_STATE_WAITING 3
+#define TASK_STATE_BROKEN  4
 
 typedef struct task task_t;
 
@@ -33,11 +34,10 @@ struct task {
        u32_t t_pgdir;
        void *t_kstack;
        u32_t t_privl;
+       u32_t t_state;
 
        u32_t t_tslice;
        u32_t t_rslice;
-
-       u32_t t_state;
 } __attribute__((packed));
 
 int     cpu_get_id(void);