Changeset 3ac5086 in mainline

Timestamp:

2012-11-24T02:08:55Z (11 years ago)

Author:

Adam Hraska <adam.hraska+hos@…>

Branches:

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

Children:

5d230a30

Parents:

d04e46e

Message:

Fixed kernel futex cleanup: now walks list via correct links and frees items once it is sure cht is not resizing.

Location:

kernel/generic

Files:

• include/adt/cht.h (modified) (1 diff)
• include/proc/task.h (modified) (1 diff)
• src/adt/cht.c (modified) (2 diffs)
• src/proc/task.c (modified) (1 diff)
• src/synch/futex.c (modified) (5 diffs)

kernel/generic/include/adt/cht.h

@@ -136 +136 @@
         size_t max_load, bool can_block, cht_ops_t *op);
 extern void cht_destroy(cht_t *h);
+extern void cht_destroy_unsafe(cht_t *h);
 
 extern cht_link_t *cht_find(cht_t *h, void *key);

kernel/generic/include/proc/task.h

@@ -129 +129 @@
         task_arch_t arch;
         
-        /** Serializes access to futex_list (independent of the task spinlock). */
-        mutex_t futex_list_lock;
-        /** List of all futexes accesses by this task. */
-        list_t futex_list;
-        /** CHT mapping virtual addresses of futex variables to futex objects. */
         struct futex_cache {
+                /** CHT mapping virtual addresses of futex variables to futex objects.*/
+                cht_t ht;
+                /** Serializes access to futex_list.*/
+                mutex_t list_lock;
+                /** List of all futexes accesses by this task. */
+                list_t list;
                 work_t destroy_work;
-                cht_t ht;
         } *futexes;
         

kernel/generic/src/adt/cht.c

@@ -617 +617 @@
 void cht_destroy(cht_t *h)
 {
+        cht_destroy_unsafe(h);
+        
+        /* You must clear the table of items. Otherwise cht_destroy will leak. */
+        ASSERT(atomic_get(&h->item_cnt) == 0);
+}
+
+/** Destroys a successfully created CHT but does no error checking. */
+void cht_destroy_unsafe(cht_t *h)
+{
         /* Wait for resize to complete. */
         while (0 < atomic_get(&h->resize_reqs)) {
@@ -627 +636 @@
         free(h->b);
         h->b = NULL;
-        
-        /* You must clear the table of items. Otherwise cht_destroy will leak. */
-        ASSERT(atomic_get(&h->item_cnt) == 0);
 }
 

kernel/generic/src/proc/task.c

@@ -165 +165 @@
         spinlock_initialize(&task->active_calls_lock, "active_calls_lock");
         list_initialize(&task->active_calls);
-        
-        mutex_initialize(&task->futex_list_lock, MUTEX_PASSIVE);
-        list_initialize(&task->futex_list);
-        
+                
 #ifdef CONFIG_UDEBUG
         /* Init kbox stuff */

kernel/generic/src/synch/futex.c

@@ -158 +158 @@
         
         cht_create(&task->futexes->ht, 0, 0, 0, true, &task_futex_ht_ops);
+        
+        list_initialize(&task->futexes->list);
+        mutex_initialize(&task->futexes->list_lock, MUTEX_PASSIVE);
 }
 
 /** Destroys the futex structures for the dying task. */
-void futex_task_deinit(struct task *task)
+void futex_task_deinit(task_t *task)
 {
         /* Interrupts are disabled so we must not block (cannot run cht_destroy). */
@@ -180 +183 @@
                 member_to_inst(work, struct futex_cache, destroy_work);
         
-        cht_destroy(&cache->ht);
+        /* 
+         * Destroy the cache before manually freeing items of the cache in case
+         * table resize is in progress.
+         */
+        cht_destroy_unsafe(&cache->ht);
+        
+        /* Manually free futex_ptr cache items. */
+        list_foreach_safe(cache->list, cur_link, next_link) {
+                futex_ptr_t *fut_ptr = member_to_inst(cur_link, futex_ptr_t, all_link);
+
+                list_remove(cur_link);
+                free(fut_ptr);
+        }
+        
         free(cache);
 }
@@ -187 +203 @@
 void futex_task_cleanup(void)
 {
+        struct futex_cache *futexes = TASK->futexes;
+        
         /* All threads of this task have terminated. This is the last thread. */
-        mutex_lock(&TASK->futex_list_lock);
-        
-        list_foreach_safe(TASK->futex_list, cur_link, next_link) {
-                futex_ptr_t *fut_ptr = member_to_inst(cur_link, futex_ptr_t, cht_link);
-                
+        mutex_lock(&futexes->list_lock);
+        
+        list_foreach_safe(futexes->list, cur_link, next_link) {
+                futex_ptr_t *fut_ptr = member_to_inst(cur_link, futex_ptr_t, all_link);
+
                 /*
                  * The function is free to free the futex. All other threads of this
@@ -202 +220 @@
                  */
                 futex_release_ref_locked(fut_ptr->futex);
-                
-                /* 
-                 * No need to remove the futex_ptr from the CHT cache of this task
-                 * because futex_task_deinit() will destroy the CHT shortly.
-                 */
-                list_remove(cur_link);
-                free(fut_ptr);
-        }
-        
-        mutex_unlock(&TASK->futex_list_lock);
+        }
+        
+        mutex_unlock(&futexes->list_lock);
 }
 
@@ -355 +366 @@
         /* Cache the mapping from the virtual address to the futex for this task. */
         if (cht_insert_unique(&TASK->futexes->ht, &fut_ptr->cht_link, &dup_link)) {
-                mutex_lock(&TASK->futex_list_lock);
-                list_append(&fut_ptr->all_link, &TASK->futex_list);
-                mutex_unlock(&TASK->futex_list_lock);
+                mutex_lock(&TASK->futexes->list_lock);
+                list_append(&fut_ptr->all_link, &TASK->futexes->list);
+                mutex_unlock(&TASK->futexes->list_lock);
         } else {
                 /* Another thread of this task beat us to it. Use that mapping instead.*/