Changeset 2569ec90 in mainline

Timestamp:

2006-06-05T18:15:30Z (18 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

b65caba1

Parents:

31e8ddd

Message:

In task_kill(), remove the task from the tasks_btree before proceeding.
Thus, when the kernel finds the task in the tasks_btree and locks it before
releasing tasks_lock, it is guaranteed that the task will not be destroyed
until the lock is held. If the kernel needs to unlock the task, do some operation
and lock it again, it should increase its refcount before doing so. In that case,
when releasing the lock, it must decrement the refcount and if it reaches
zero, it must call task_destroy().

Location:

generic/src

Files:

• ddi/ddi.c (modified) (1 diff)
• proc/task.c (modified) (2 diffs)
• security/cap.c (modified) (3 diffs)

generic/src/ddi/ddi.c

@@ -136 +136 @@
         }
 
-        /*
-         * TODO: We are currently lacking support for task destroying.
-         * Once it is added to the kernel, we must take care to
-         * synchronize in a way that prevents race conditions here.
-         */
-        
         /* Lock the task and release the lock protecting tasks_btree. */
         spinlock_lock(&t->lock);

generic/src/proc/task.c

@@ -141 +141 @@
 void task_destroy(task_t *t)
 {
-        spinlock_lock(&tasks_lock);
-        btree_remove(&tasks_btree, t->taskid, NULL);
-        spinlock_unlock(&tasks_lock);
-
         task_destroy_arch(t);
         btree_destroy(&t->futexes);
@@ -275 +271 @@
                 return ENOENT;
         }
-        
+
         spinlock_lock(&ta->lock);
         ta->refcount++;
         spinlock_unlock(&ta->lock);
 
+        btree_remove(&tasks_btree, ta->taskid, NULL);
         spinlock_unlock(&tasks_lock);
         

generic/src/security/cap.c

@@ -113 +113 @@
                 return (__native) ENOENT;
         }
+        
+        spinlock_lock(&t->lock);
+        cap_set(t, cap_get(t) | caps);
+        spinlock_unlock(&t->lock);
+        
         spinlock_unlock(&tasks_lock);
         
-        cap_set(t, cap_get(t) | caps);
+
         
         interrupts_restore(ipl);        
@@ -150 +155 @@
                 return (__native) ENOENT;
         }
-        spinlock_unlock(&tasks_lock);
 
         /*
@@ -158 +162 @@
          */
         if (!(cap_get(TASK) & CAP_CAP) || !(t == TASK)) {
+                spinlock_unlock(&tasks_lock);
                 interrupts_restore(ipl);
                 return (__native) EPERM;
         }
+        
+        spinlock_lock(&t->lock);
+        cap_set(t, cap_get(t) & ~caps);
+        spinlock_unlock(&t->lock);
 
-        cap_set(t, cap_get(t) & ~caps);
-        
+        spinlock_unlock(&tasks_lock);
+
         interrupts_restore(ipl);
         return 0;