exit() almost there.

- Implemented reasonable way to suspend task.
  - A task that has a pending suspend would be interrupted
    from its sleep via the suspender task.
  - If suspend was raised and right after, task became about to sleep,
    then scheduler wakes it up.
  - If suspend was raised when task was in user mode, then an irq suspends it.
  - Also suspends are checked at the end of a syscall so that if suspend was
    raised because of a syscall from the task, the task is suspended before it
    goes back to user mode.

  - This mechanism is very similar to signals, and it may lead as a base for
    implementing signal handling.

- Implemented common vma dropping for shadow vm object dropping and task exiting.

tasks/libposix/exit.c

@@ -5,20 +5,22 @@
 #include <unistd.h>
 #include <l4/macros.h>
 
-static inline void l4_exit(int status)
+static inline void __attribute__ ((noreturn)) l4_exit(int status)
 {
-	int err;
+	int ret;
 
 	write_mr(L4SYS_ARG0, status);
 
-	/* Call pager with exit() request. */
-	err = l4_send(PAGER_TID, L4_IPC_TAG_EXIT);
-	printf("%s: L4 IPC Error: %d.\n", __FUNCTION__, err);
+	/* Call pager with exit() request and block on its receive phase */
+	ret = l4_sendrecv(PAGER_TID, PAGER_TID, L4_IPC_TAG_EXIT);
+
 	/* This call should not fail or return */
+	printf("%s: L4 IPC returned: %d.\n", __FUNCTION__, ret);
 	BUG();
 }
 
-void exit(int status)
+void __attribute__ ((noreturn)) _exit(int status)
 {
 	l4_exit(status);
 }
+

tasks/mm0/main.c

@@ -123,6 +123,11 @@ void handle_requests(void)
 		ret = sys_fork(sender);
 		break;
 	}
+	case L4_IPC_TAG_EXIT: {
+		/* An exiting task has no receive phase */
+		sys_exit(sender, (int)mr[0]);
+		return;
+	}
 	case L4_IPC_TAG_BRK: {
 //		ret = sys_brk(sender, (void *)mr[0]);
 //		break;

tasks/mm0/src/fault.c

@@ -365,7 +365,20 @@ int vma_drop_merge_delete(struct vm_area *vma, struct vm_obj_link *link)
 /* This version is used when exiting. */
 int vma_drop_merge_delete_all(struct vm_area *vma)
 {
-	struct vm_obj_link *vmo_link;
+	struct vm_obj_link *vmo_link, *n;
+
+	/* Vma cannot be empty */
+	BUG_ON(list_empty(&vma->vm_obj_list));
+
+	/* Traverse and get rid of all links */
+	list_for_each_entry_safe(vmo_link, n, &vma->vm_obj_list, list)
+		vma_drop_merge_delete(vma, vmo_link);
+
+	return 0;
+}
+int vma_drop_merge_delete_all_old(struct vm_area *vma)
+{
+	struct vm_obj_link *vmo_link, *n;
 
 	/* Get the first link on the vma */
 	BUG_ON(list_empty(&vma->vm_obj_list));
@@ -373,6 +386,9 @@ int vma_drop_merge_delete_all(struct vm_area *vma)
 			      struct vm_obj_link, list);
 
 	/* Traverse and get rid of all links */
+	list_for_each_entry_safe(vmo_link, n, &vma->vm_obj_list, list) {
+		vma_drop_merge_delete(vma, vmo_link);
+	}
 	do {
 		vma_drop_merge_delete(vma, vmo_link);
 
@@ -382,6 +398,7 @@ int vma_drop_merge_delete_all(struct vm_area *vma)
 	return 0;
 }
 
+
 /* TODO:
  * - Why not allocate a swap descriptor in vma_create_shadow() rather than
  *   a bare vm_object? It will be needed.

tasks/mm0/src/shm.c

@@ -106,19 +106,6 @@ static void *do_shmat(struct vm_file *shm_file, void *shm_addr, int shmflg,
 	return shm->shm_addr;
 }
 
-/* TODO: Do we need this?
- * MM0 never needs a task's utcb page. vfs needs it.
- * UTCBs get special treatment here. If the task
- * is attaching to its utcb, mm0 prefaults it so
- * that it can access it later on whether or not
- * the task makes a syscall to mm0 without first
- * faulting the utcb.
- */
-/*
-	if ((unsigned long)shmaddr == task->utcb_address)
-		utcb_prefault(task, VM_READ | VM_WRITE);
-*/
-
 void *sys_shmat(struct tcb *task, l4id_t shmid, void *shmaddr, int shmflg)
 {
 	struct vm_file *shm_file, *n;

tasks/mm0/src/utcb.c

@@ -1,9 +1,8 @@
 /*
- * Utcb address allocation for user tasks.
+ * utcb address allocation for user tasks.
  *
  * Copyright (C) 2008 Bahadir Balban
  */
-
 #include <stdio.h>
 #include <utcb.h>
 #include <lib/addr.h>
@@ -71,44 +70,3 @@ void *task_send_utcb_address(struct tcb *sender, l4id_t taskid)
 	return 0;
 }
 
-#if 0
-
-To be ditched
-/*
- * Triggered during a sys_shmat() by a client task when mapping its utcb.
- * This prefaults the utcb and maps it in to mm0 so that it can freely
- * access it anytime later.
- */
-int utcb_prefault(struct tcb *task, unsigned int vmflags)
-{
-	int err;
-	struct page *pg;
-
-	/* First map in the page to task with given flags, e.g. read/write */
-	if ((err = prefault_page(task, task->utcb_address, vmflags)) < 0) {
-		printf("%s: Failed: %d\n", __FUNCTION__, err);
-		return err;
-	}
-
-	/*
-	 * Get the topmost page. Since we did both a VM_READ and VM_WRITE
-	 * prefault, this gets a writeable instead of a read-only page.
-	 */
-	pg = task_virt_to_page(task, task->utcb_address);
-	if (!pg || IS_ERR(pg)) {
-		printf("%s: Cannot retrieve task %d's utcb page.\n",
-		       __FUNCTION__, task->tid);
-		BUG();
-	}
-
-	/* Map it in to self */
-	l4_map((void *)page_to_phys(pg), (void *)task->utcb_address, 1,
-	       MAP_USR_RW_FLAGS, self_tid());
-
-	/* Flag that says this task's utcb is mapped to mm0 as r/w */
-	task->utcb_mapped = 1;
-
-	return 0;
-}
-
-#endif

tasks/test0/src/forktest.c

@@ -32,7 +32,7 @@ int forktest(void)
 	printf("PID: %d, my global: %d\n", myid, global);
 	printf("-- PASSED --\n");
 out:
-	while(1)
-		;
+	printf("PID: %d exiting...\n", myid);
+	_exit(0);
 }