summaryrefslogtreecommitdiffstats
path: root/lock_free_queue.c
diff options
context:
space:
mode:
Diffstat (limited to 'lock_free_queue.c')
-rw-r--r--lock_free_queue.c157
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;
}
generated by cgit v1.1-2-g2b99 at 2024-11-21 13:31:32 +0100