cleanup lock_free_queue

1 files changed, 86 insertions, 71 deletions

diff --git a/lock_free_queue.c b/lock_free_queue.c
index e3e128f..a21d1ce 100644
--- a/lock_free_queue.c
+++ b/lock_free_queue.c
@@ -1,7 +1,7 @@
 /*
  * File     : lock_free_queue.c
  * Author   : Jérémy Zurcher  <jeremy@asynk.ch>
- * Date     : 01/11/09 
+ * Date     : 2009/11/01
  * License  : stolen from http://www.cs.rochester.edu/~scott/papers/1996_PODC_queues.pdf
  */
 
@@ -14,87 +14,102 @@
 /* CMPXCHG8B m64   Compare EDX:EAX with m64. If equal, set ZF and load ECX:EBX into m64. Else, clear ZF and load m64 into EDX:EAX. */
 static inline unsigned int compare_and_swap(volatile unsigned long long *mem,
                                             volatile unsigned long long old,
-                                            volatile unsigned long long new) {
-    char result;
-    __asm__ __volatile__("lock; cmpxchg8b %0; setz %1;"
+                                            volatile unsigned long long new)
+{
+   char result;
+   __asm__ __volatile__("lock; cmpxchg8b %0; setz %1;"
             : "=m"(*mem), "=q"(result)
-            : "m"(*mem), "d" ((unsigned long)(old>>32)), "a" ((unsigned long)old),
-            "c" ((unsigned long)(new>>32)), "b" ((unsigned long)new)
+            : "m"(*mem), "d" ((unsigned long)(old>>32)), "a" ((unsigned long)old)
+            , "c" ((unsigned long)(new>>32)), "b" ((unsigned long)new)
             : "memory");
-    return (int)result;
+   return (int)result;
 }
 
-void init( lfq_t *q ) {
-    node_t *node = (node_t*)malloc(sizeof(node_t));
-    node->next.split.ptr = NULL;
-    node->next.split.count = 0;
-    q->head.split.ptr = q->tail.split.ptr = node;
-    q->head.split.count = q->tail.split.count = 0;
+void init(lfq_t *q)
+{
+   node_t *node = (node_t*)malloc(sizeof(node_t));
+   node->next.split.ptr = NULL;
+   node->next.split.count = 0;
+   q->head.split.ptr = q->tail.split.ptr = node;
+   q->head.split.count = q->tail.split.count = 0;
 }
 
-void enqueue( lfq_t *q, void *data ) {
-    node_t *node;
-    pointer_t tail;
-    pointer_t next;
-    pointer_t tmp;
+void enqueue(lfq_t *q, void *data)
+{
+   node_t *node;
+   pointer_t tail;
+   pointer_t next;
+   pointer_t tmp;
 
-    node = (node_t*)malloc(sizeof(node_t));
-    node->data = data;
-    node->next.split.ptr = NULL;
-    /* node->next.split.count = 0; */
-    for(;;) {
-        tail.concat = q->tail.concat;                   /* copy tail pointer */
-        next.concat = tail.split.ptr->next.concat;      /* copy next pointer */
-        if (tail.concat == q->tail.concat) {            /* tail is still consistent */
-            if (next.split.ptr == NULL) {               /* next is still the last node */
-                /* if tail->next is the same as next, link node at the end of the list */
-                tmp.split.ptr = node;
-                tmp.split.count = next.split.count+1;
-                if ( compare_and_swap( &tail.split.ptr->next.concat, next.concat, tmp.concat ) ) break;
-            } else {
-                /* try to swing tail to the next node, if q-> tail is still tail => next is ok */
-                tmp.split.ptr = next.split.ptr;
-                tmp.split.count = tail.split.count+1;
-                compare_and_swap( &q->tail.concat, tail.concat, tmp.concat );
-            }
-        }
-    }
-    /* try to swing tail to the next node, may have been done by a concurrent push */
-    tmp.split.ptr = node;
-    tmp.split.count = tail.split.count+1;
-    compare_and_swap( &q->tail.concat, tail.concat, tmp.concat );
+   node = (node_t*)malloc(sizeof(node_t));
+   node->data = data;
+   node->next.split.ptr = NULL;
+   /* node->next.split.count = 0; */
+   for(;;)
+     {
+        tail.concat = q->tail.concat;                 /* copy tail pointer */
+        next.concat = tail.split.ptr->next.concat;    /* copy next pointer */
+        if (tail.concat == q->tail.concat)
+          {                                           /* tail is still consistent */
+             if (next.split.ptr == NULL)
+               {                                      /* next is still the last node */
+                  /* if tail->next is the same as next, link node at the end of the list */
+                  tmp.split.ptr = node;
+                  tmp.split.count = next.split.count+1;
+                  if ( compare_and_swap( &tail.split.ptr->next.concat, next.concat, tmp.concat ) ) break;
+               }
+             else
+               {
+                  /* try to swing tail to the next node, if q-> tail is still tail => next is ok */
+                  tmp.split.ptr = next.split.ptr;
+                  tmp.split.count = tail.split.count+1;
+                  compare_and_swap( &q->tail.concat, tail.concat, tmp.concat );
+               }
+          }
+     }
+   /* try to swing tail to the next node, may have been done by a concurrent push */
+   tmp.split.ptr = node;
+   tmp.split.count = tail.split.count+1;
+   compare_and_swap( &q->tail.concat, tail.concat, tmp.concat );
 }
 
-void* dequeue( lfq_t *q ) {
-    void *data;
-    pointer_t head;
-    pointer_t tail;
-    node_t *next;
-    pointer_t tmp;
-    
-    for(;;) {
+void* dequeue(lfq_t *q)
+{
+   void *data;
+   pointer_t head;
+   pointer_t tail;
+   node_t *next;
+   pointer_t tmp;
+
+   for(;;)
+     {
         head.concat = q->head.concat;
         tail.concat = q->tail.concat;
         next = (node_t *)head.split.ptr;
-        if (head.concat == q->head.concat) {
-            if (head.split.ptr == tail.split.ptr) {     /* still consistent */
-                if (next->next.split.ptr == NULL) {     /* queue empty */
-                    return NULL;
-                }
-                /* new node has been linked, but tail is behind, should advance it */
-                tmp.split.ptr = next->next.split.ptr;
-                tmp.split.count = tail.split.count+1;
-                compare_and_swap( &q->tail.concat, tail.concat, tmp.concat );
-            } else {
-                data = next->data;
-                /* try to swing head to the next node */
-                tmp.split.ptr = next->next.split.ptr;
-                tmp.split.count = head.split.count+1;
-                if( compare_and_swap( &q->head.concat, head.concat, tmp.concat ) ) break;
-            }
-        }
-    }
-    free((void*)head.split.ptr);
-    return data;
+        if (head.concat == q->head.concat)
+          {
+             if (head.split.ptr == tail.split.ptr)
+               {     /* still consistent */
+                  if (next->next.split.ptr == NULL)
+                    {     /* queue empty */
+                       return NULL;
+                    }
+                  /* new node has been linked, but tail is behind, should advance it */
+                  tmp.split.ptr = next->next.split.ptr;
+                  tmp.split.count = tail.split.count+1;
+                  compare_and_swap( &q->tail.concat, tail.concat, tmp.concat );
+               }
+             else
+               {
+                  data = next->data;
+                  /* try to swing head to the next node */
+                  tmp.split.ptr = next->next.split.ptr;
+                  tmp.split.count = head.split.count+1;
+                  if( compare_and_swap( &q->head.concat, head.concat, tmp.concat ) ) break;
+               }
+          }
+     }
+   free((void*)head.split.ptr);
+   return data;
 }