make linked-list traversable in signal handlers

[Bruno Haible]

Hi,

I committed this patch, using 'volatile' to avoid instruction reordering.


2006-07-23  Bruno Haible  <address@hidden>

        * gl_anylinked_list2.h (ASYNCSAFE): New macro.
        (gl_linked_add_first, gl_linked_add_last, gl_linked_add_before,
        gl_linked_add_after, gl_linked_add_at, gl_linked_remove_node,
        gl_linked_remove_at): Use it.

*** GNULIB/gnulib-20060722-modified/lib/gl_anylinked_list2.h    2006-07-17 
13:27:18.000000000 +0200
--- GETTEXT/gettext-work/gettext-6/gettext-tools/lib/gl_anylinked_list2.h       
2006-07-23 00:50:01.000000000 +0200
***************
*** 18,23 ****
--- 18,40 ----
  
  /* Common code of gl_linked_list.c and gl_linkedhash_list.c.  */
  
+ /* If the symbol SIGNAL_SAFE_LIST is defined, the code is compiled in such
+    a way that a gl_list_t data structure may be used from within a signal
+    handler.  The operations allowed in the signal handler are:
+      gl_list_iterator, gl_list_iterator_next, gl_list_iterator_free.
+    The list and node fields that are therefore accessed from the signal 
handler
+    are:
+      list->root, node->next, node->value.
+    We are careful to make modifications to these fields only in an order
+    that maintains the consistency of the list data structure at any moment,
+    and we use 'volatile' assignments to prevent the compiler from reordering
+    such assignments.  */
+ #ifdef SIGNAL_SAFE_LIST
+ # define ASYNCSAFE(type) *(volatile type *)&
+ #else
+ # define ASYNCSAFE(type)
+ #endif
+ 
  /* -------------------------- gl_list_t Data Type -------------------------- 
*/
  
  static gl_list_t
***************
*** 396,402 ****
    gl_list_node_t node =
      (struct gl_list_node_impl *) xmalloc (sizeof (struct gl_list_node_impl));
  
!   node->value = elt;
  #if WITH_HASHTABLE
    node->h.hashcode =
      (list->base.hashcode_fn != NULL
--- 413,419 ----
    gl_list_node_t node =
      (struct gl_list_node_impl *) xmalloc (sizeof (struct gl_list_node_impl));
  
!   ASYNCSAFE(const void *) node->value = elt;
  #if WITH_HASHTABLE
    node->h.hashcode =
      (list->base.hashcode_fn != NULL
***************
*** 409,417 ****
  
    /* Add node to the list.  */
    node->prev = &list->root;
!   node->next = list->root.next;
    node->next->prev = node;
!   list->root.next = node;
    list->count++;
  
  #if WITH_HASHTABLE
--- 426,434 ----
  
    /* Add node to the list.  */
    node->prev = &list->root;
!   ASYNCSAFE(gl_list_node_t) node->next = list->root.next;
    node->next->prev = node;
!   ASYNCSAFE(gl_list_node_t) list->root.next = node;
    list->count++;
  
  #if WITH_HASHTABLE
***************
*** 427,433 ****
    gl_list_node_t node =
      (struct gl_list_node_impl *) xmalloc (sizeof (struct gl_list_node_impl));
  
!   node->value = elt;
  #if WITH_HASHTABLE
    node->h.hashcode =
      (list->base.hashcode_fn != NULL
--- 444,450 ----
    gl_list_node_t node =
      (struct gl_list_node_impl *) xmalloc (sizeof (struct gl_list_node_impl));
  
!   ASYNCSAFE(const void *) node->value = elt;
  #if WITH_HASHTABLE
    node->h.hashcode =
      (list->base.hashcode_fn != NULL
***************
*** 439,447 ****
  #endif
  
    /* Add node to the list.  */
!   node->next = &list->root;
    node->prev = list->root.prev;
!   node->prev->next = node;
    list->root.prev = node;
    list->count++;
  
--- 456,464 ----
  #endif
  
    /* Add node to the list.  */
!   ASYNCSAFE(gl_list_node_t) node->next = &list->root;
    node->prev = list->root.prev;
!   ASYNCSAFE(gl_list_node_t) node->prev->next = node;
    list->root.prev = node;
    list->count++;
  
***************
*** 458,464 ****
    gl_list_node_t new_node =
      (struct gl_list_node_impl *) xmalloc (sizeof (struct gl_list_node_impl));
  
!   new_node->value = elt;
  #if WITH_HASHTABLE
    new_node->h.hashcode =
      (list->base.hashcode_fn != NULL
--- 475,481 ----
    gl_list_node_t new_node =
      (struct gl_list_node_impl *) xmalloc (sizeof (struct gl_list_node_impl));
  
!   ASYNCSAFE(const void *) new_node->value = elt;
  #if WITH_HASHTABLE
    new_node->h.hashcode =
      (list->base.hashcode_fn != NULL
***************
*** 470,478 ****
  #endif
  
    /* Add new_node to the list.  */
!   new_node->next = node;
    new_node->prev = node->prev;
!   new_node->prev->next = new_node;
    node->prev = new_node;
    list->count++;
  
--- 487,495 ----
  #endif
  
    /* Add new_node to the list.  */
!   ASYNCSAFE(gl_list_node_t) new_node->next = node;
    new_node->prev = node->prev;
!   ASYNCSAFE(gl_list_node_t) new_node->prev->next = new_node;
    node->prev = new_node;
    list->count++;
  
***************
*** 489,495 ****
    gl_list_node_t new_node =
      (struct gl_list_node_impl *) xmalloc (sizeof (struct gl_list_node_impl));
  
!   new_node->value = elt;
  #if WITH_HASHTABLE
    new_node->h.hashcode =
      (list->base.hashcode_fn != NULL
--- 506,512 ----
    gl_list_node_t new_node =
      (struct gl_list_node_impl *) xmalloc (sizeof (struct gl_list_node_impl));
  
!   ASYNCSAFE(const void *) new_node->value = elt;
  #if WITH_HASHTABLE
    new_node->h.hashcode =
      (list->base.hashcode_fn != NULL
***************
*** 502,510 ****
  
    /* Add new_node to the list.  */
    new_node->prev = node;
!   new_node->next = node->next;
    new_node->next->prev = new_node;
!   node->next = new_node;
    list->count++;
  
  #if WITH_HASHTABLE
--- 519,527 ----
  
    /* Add new_node to the list.  */
    new_node->prev = node;
!   ASYNCSAFE(gl_list_node_t) new_node->next = node->next;
    new_node->next->prev = new_node;
!   ASYNCSAFE(gl_list_node_t) node->next = new_node;
    list->count++;
  
  #if WITH_HASHTABLE
***************
*** 526,532 ****
  
    new_node =
      (struct gl_list_node_impl *) xmalloc (sizeof (struct gl_list_node_impl));
!   new_node->value = elt;
  #if WITH_HASHTABLE
    new_node->h.hashcode =
      (list->base.hashcode_fn != NULL
--- 543,549 ----
  
    new_node =
      (struct gl_list_node_impl *) xmalloc (sizeof (struct gl_list_node_impl));
!   ASYNCSAFE(const void *) new_node->value = elt;
  #if WITH_HASHTABLE
    new_node->h.hashcode =
      (list->base.hashcode_fn != NULL
***************
*** 546,554 ****
        for (; position > 0; position--)
        node = node->next;
        new_node->prev = node;
!       new_node->next = node->next;
        new_node->next->prev = new_node;
!       node->next = new_node;
      }
    else
      {
--- 563,571 ----
        for (; position > 0; position--)
        node = node->next;
        new_node->prev = node;
!       ASYNCSAFE(gl_list_node_t) new_node->next = node->next;
        new_node->next->prev = new_node;
!       ASYNCSAFE(gl_list_node_t) node->next = new_node;
      }
    else
      {
***************
*** 558,566 ****
        node = &list->root;
        for (; position > 0; position--)
        node = node->prev;
!       new_node->next = node;
        new_node->prev = node->prev;
!       new_node->prev->next = new_node;
        node->prev = new_node;
      }
    list->count++;
--- 575,583 ----
        node = &list->root;
        for (; position > 0; position--)
        node = node->prev;
!       ASYNCSAFE(gl_list_node_t) new_node->next = node;
        new_node->prev = node->prev;
!       ASYNCSAFE(gl_list_node_t) new_node->prev->next = new_node;
        node->prev = new_node;
      }
    list->count++;
***************
*** 587,593 ****
    prev = node->prev;
    next = node->next;
  
!   prev->next = next;
    next->prev = prev;
    list->count--;
  
--- 604,610 ----
    prev = node->prev;
    next = node->next;
  
!   ASYNCSAFE(gl_list_node_t) prev->next = next;
    next->prev = prev;
    list->count--;
  
***************
*** 615,621 ****
        node = node->next;
        removed_node = node->next;
        after_removed = node->next->next;
!       node->next = after_removed;
        after_removed->prev = node;
      }
    else
--- 632,638 ----
        node = node->next;
        removed_node = node->next;
        after_removed = node->next->next;
!       ASYNCSAFE(gl_list_node_t) node->next = after_removed;
        after_removed->prev = node;
      }
    else
***************
*** 630,636 ****
        removed_node = node->prev;
        before_removed = node->prev->prev;
        node->prev = before_removed;
!       before_removed->next = node;
      }
  #if WITH_HASHTABLE
    remove_from_bucket (list, removed_node);
--- 647,653 ----
        removed_node = node->prev;
        before_removed = node->prev->prev;
        node->prev = before_removed;
!       ASYNCSAFE(gl_list_node_t) before_removed->next = node;
      }
  #if WITH_HASHTABLE
    remove_from_bucket (list, removed_node);