more fixes

core/sched/sched_dumb.c

@@ -8,6 +8,7 @@
 #include <zinnia/print.h>
 #include <zinnia/sched.h>
 #include <zinnia/spin.h>
+#include <zinnia/stack.h>
 #include <zinnia/string.h>
 #include <zinnia/tailq.h>
 #include <zinnia/vma.h>
@@ -67,6 +68,11 @@ static struct task* next_task(struct scheduler* sched) {
     return t;
 }
 
+static void finish_switch(struct task* prev) {
+    if (prev->state == TASK_STATE_DEAD)
+        task_destroy(prev);
+}
+
 static void do_reschedule(struct scheduler* sched) {
     struct task* from = sched->current;
     struct task* to = next_task(sched);
@@ -82,12 +88,13 @@ static void do_reschedule(struct scheduler* sched) {
 
     struct percpu* cpu = percpu_get();
     from->user_stack = cpu->user_stack;
-    cpu->kernel_stack = to->kernel_stack + KERNEL_STACK_SIZE;
+    cpu->kernel_stack = kernel_stack_top(&to->kernel_stack);
     cpu->user_stack = to->user_stack;
 
     struct irq_percpu irq_state = *percpu_ref(irq_data);
-    arch_sched_switch(from, to);
+    struct task* prev = arch_sched_switch(from, to);
     *percpu_ref(irq_data) = irq_state;
+    finish_switch(prev);
     irq_unlock();
 }
 
@@ -117,17 +124,17 @@ errno_t task_create(const char* name, struct vma* space, task_fn_t entry, uintpt
     strncpy(new_task->name, name, sizeof(new_task->name));
 
     // Allocate a kernel stack.
-    new_task->kernel_stack = (uintptr_t)mem_alloc(KERNEL_STACK_SIZE, 0);
-    if (!new_task->kernel_stack) {
+    errno_t s = stack_init(&new_task->kernel_stack, KERNEL_STACK_SIZE);
+    if (s != 0) {
         mem_free(new_task);
-        return ENOMEM;
+        return s;
     }
     new_task->user_stack = 0;
 
     // Initialize the arch-dependent parts.
-    errno_t s = arch_task_init(&new_task->context, entry, arg0, new_task->kernel_stack + KERNEL_STACK_SIZE, true);
+    s = arch_task_init(&new_task->context, entry, arg0, kernel_stack_top(&new_task->kernel_stack), true);
     if (s != 0) {
-        mem_free((void*)new_task->kernel_stack);
+        stack_destroy(&new_task->kernel_stack);
         mem_free(new_task);
         return s;
     }
@@ -136,7 +143,15 @@ errno_t task_create(const char* name, struct vma* space, task_fn_t entry, uintpt
     return 0;
 }
 
-void task_entry(task_fn_t entry, uintptr_t arg0) {
+void task_destroy(struct task* task) {
+    arch_task_fini(&task->context);
+    stack_destroy(&task->kernel_stack);
+    mem_free(task);
+}
+
+void task_entry(task_fn_t entry, uintptr_t arg0, struct task* prev) {
+    finish_switch(prev);
+
     *percpu_ref(irq_data) = (struct irq_percpu){
         .depth = 1,
         .saved_state = true,