Listing 2. Algorithm of Entering Watermark States

1 static void enter_watermark_state(int new_state)
2 {
3   int changed = 0, r;
4
5   spin_lock(&lowmem_lock);
6   if (lowmem_watermark_reached != new_state) {
7     lowmem_watermark_reached = new_state;
8     changed = 1;
9   }
10  spin_unlock(&lowmem_lock);
11  if (changed) {
12    printk(KERN_DEBUG MY_NAME ": changed to %d\n",
13          new_state);
14    r = kobject_uevent(&kernel_subsys.kset.kobj,
15                       KOBJ_CHANGE,
16                       &low_watermark_attr.attr);
17    if (r < 0)
18      printk(KERN_ERR MY_NAME
19            ": kobject_uevent failed: %d\n", r);
19    }
20  }