Linked lists

tasks/linked_lists/module.c

@@ -8,6 +8,27 @@
 #include "stack.h"
 #include "assert.h"
 
+void clear_process_list(struct list_head *stack)
+{
+    stack_entry_t* cur;
+
+    while (!stack_empty(stack))
+    {
+        cur = stack_pop(stack);
+        kfree(STACK_ENTRY_DATA(cur, char*));
+        delete_stack_entry(cur);
+    }
+}
+
+#define CHECK_NOT_NULL(ptr, stack_top, ret) \
+    if (!ptr) \
+    { \
+        clear_process_list(&stack_top); \
+        ret = -ENOMEM; \
+        break; \
+    }
+
+
 static int __init test_stack(void)
 {
     int ret = 0;
@@ -32,7 +53,7 @@ static int __init test_stack(void)
         tos = stack_pop(&data_stack);
         tos_data = STACK_ENTRY_DATA(tos, const char*);
         delete_stack_entry(tos);
-        printk(KERN_ALERT "%s == %s\n", tos_data, test_data[i]);
+        printk(KERN_ALERT "!%s! == !%s!\n", tos_data, test_data[i]);
         assert(!strcmp(tos_data, test_data[i]));
     }
 
@@ -45,8 +66,38 @@ static int __init test_stack(void)
 
 static int __init print_processes_backwards(void)
 {
-    // TODO
-    return -ENODEV;
+    int ret = 0;
+    LIST_HEAD(data_stack);
+    stack_entry_t *cur = NULL;
+    struct task_struct *p;
+    char* name;
+
+    for_each_process(p)
+    {
+        // Get the name.
+        char* data = kmalloc(sizeof(p->comm), GFP_KERNEL);
+        CHECK_NOT_NULL(data, data_stack, ret)
+
+        CHECK_NOT_NULL(get_task_comm(data, p), data_stack, ret)
+
+        // Put to stack.
+        cur = create_stack_entry(data);
+        CHECK_NOT_NULL(cur, data_stack, ret)
+
+        stack_push(&data_stack, cur);
+    }
+
+    printk(KERN_ALERT "Hopefully now here appears the list of files in reversed order");
+    while (!stack_empty(&data_stack))
+    {
+        cur = stack_pop(&data_stack);
+        name = STACK_ENTRY_DATA(cur, char*);
+        delete_stack_entry(cur);
+        printk(KERN_ALERT "Yet another file: %s\n", name);
+        kfree(name);
+    }
+
+    return ret;
 }
 
 static int __init ll_init(void)

tasks/linked_lists/stack.c

@@ -1,28 +1,38 @@
 #include "stack.h"
 
+#include "assert.h"
+#include <linux/slab.h>
+#include <linux/gfp.h>
+
 stack_entry_t* create_stack_entry(void *data)
 {
-    // TODO
-    (void)data;
-    return NULL;
+    stack_entry_t* result = kmalloc(sizeof(stack_entry_t), GFP_KERNEL);
+    if (!result) {
+        printk(KERN_ALERT "FAILED TO ALLOCATE MEMORY");
+        return result;
+    }
+    INIT_LIST_HEAD(&(result->lh));
+    result->data = data;
+    printk(KERN_ALERT "created node: %p\n", result);
+    return result;
 }
 
 void delete_stack_entry(stack_entry_t *entry)
 {
-    // TODO
-    (void)entry;
+    // if I understand correctly, taking care of *data
+    // is not our responsibility, since we didn't create it
+    printk(KERN_ALERT "deleting node: %p\n", entry);
+    kfree(entry);
 }
 
 void stack_push(struct list_head *stack, stack_entry_t *entry)
 {
-    // TODO
-    (void)stack;
-    (void)entry;
+    list_add(&(entry->lh), stack);
 }
 
 stack_entry_t* stack_pop(struct list_head *stack)
 {
-    // TODO
-    (void)stack;
-    return NULL;
+    stack_entry_t* result = list_entry(stack->next, stack_entry_t, lh);
+    list_del(stack->next);
+    return result;
 }

tasks/linked_lists/stack.h

@@ -20,6 +20,6 @@ stack_entry_t* stack_pop(struct list_head *stack);
 #define STACK_ENTRY_DATA_RESET(stack_entry, new_data) \
     do { \
         (stack_entry)->data = new_data; \
-    } while(0)
+    } while(0)    
 
 #endif //_LL_STACK_H