*/
#include <stdio.h>
#include <string.h>
-#include <sys/time.h>
#include "common.h"
-#include "lwt.h"
+#include "struct.h"
#include "mem.h"
-#define NUM_ITERATIONS 10000000
-
-#define PLACE_MARK(x) (((size_t)(x))|1)
-#define CLEAR_MARK(x) (((size_t)(x))&~(size_t)1)
-#define IS_MARKED(x) ((size_t)(x))&1
-
typedef struct node {
+ uint64_t key;
+ uint64_t value;
struct node *next;
- int key;
} node_t;
-typedef struct list {
- node_t head[1];
- node_t last;
-} list_t;
-
-static void list_node_init (node_t *item, int key) {
- memset(item, 0, sizeof(node_t));
- item->key = key;
-}
+struct ll {
+ node_t *head;
+};
-node_t *list_node_alloc (int key) {
+static node_t *node_alloc (uint64_t key, uint64_t value) {
node_t *item = (node_t *)nbd_malloc(sizeof(node_t));
- list_node_init(item, key);
+ memset(item, 0, sizeof(node_t));
+ item->key = key;
+ item->value = value;
return item;
}
-list_t *list_alloc (void) {
- list_t *list = (list_t *)nbd_malloc(sizeof(list_t));
- list_node_init(list->head, INT_MIN);
- list_node_init(&list->last, INT_MAX);
- list->head->next = &list->last;
- return list;
+list_t *ll_alloc (void) {
+ list_t *ll = (list_t *)nbd_malloc(sizeof(list_t));
+ ll->head = node_alloc((uint64_t)-1, 0);
+ ll->head->next = NULL;
+ return ll;
}
-static void find_pred_and_item (node_t **pred_ptr, node_t **item_ptr, list_t *list, int key) {
- node_t *pred = list->head;
- node_t *item = list->head->next; // head is never removed
- TRACE("l3", "find_pred_and_item: searching for key %llu in list (head is %p)", key, pred);
-#ifndef NDEBUG
- int count = 0;
-#endif
- do {
- // skip removed items
- node_t *other, *next = item->next;
- TRACE("l3", "find_pred_and_item: visiting item %p (next is %p)", item, next);
- while (EXPECT_FALSE(IS_MARKED(next))) {
-
- // assist in unlinking partially removed items
- if ((other = SYNC_CAS(&pred->next, item, CLEAR_MARK(next))) != item)
- {
- TRACE("l3", "find_pred_and_item: failed to unlink item from pred %p, pred's next pointer was changed to %p", pred, other);
- return find_pred_and_item(pred_ptr, item_ptr, list, key); // retry
+static node_t *find_pred (node_t **pred_ptr, list_t *ll, uint64_t key, int help_remove) {
+ node_t *pred = ll->head;
+ node_t *item = pred->next;
+ TRACE("l3", "find_pred: searching for key %p in ll (head is %p)", key, pred);
+
+ while (item != NULL) {
+ node_t *next = item->next;
+ TRACE("l3", "find_pred: visiting item %p (next %p)", item, next);
+ TRACE("l3", "find_pred: key %p", item->key, item->value);
+
+ // Marked items are logically removed, but not unlinked yet.
+ while (EXPECT_FALSE(IS_TAGGED(next))) {
+
+ // Skip over partially removed items.
+ if (!help_remove) {
+ item = (node_t *)STRIP_TAG(item->next);
+ if (EXPECT_FALSE(item == NULL))
+ break;
+ next = item->next;
+ continue;
}
- assert(count++ < 18);
- item = (node_t *)CLEAR_MARK(next);
- next = item->next;
- TRACE("l3", "find_pred_and_item: unlinked item, %p is the new item (next is %p)", item, next);
+ // Unlink partially removed items.
+ node_t *other;
+ if ((other = SYNC_CAS(&pred->next, item, STRIP_TAG(next))) == item) {
+ item = (node_t *)STRIP_TAG(next);
+ if (EXPECT_FALSE(item == NULL))
+ break;
+ next = item->next;
+ TRACE("l3", "find_pred: unlinked item %p from pred %p", item, pred);
+ TRACE("l3", "find_pred: now item is %p next is %p", item, next);
+
+ // The thread that completes the unlink should free the memory.
+ nbd_defer_free(other);
+ } else {
+ TRACE("l3", "find_pred: lost race to unlink from pred %p; its link changed to %p", pred, other);
+ if (IS_TAGGED(other))
+ return find_pred(pred_ptr, ll, key, help_remove); // retry
+ item = other;
+ if (EXPECT_FALSE(item == NULL))
+ break;
+ next = item->next;
+ }
}
+ if (EXPECT_FALSE(item == NULL))
+ break;
+
+ // If we reached the key (or passed where it should be), we found the right predesssor
if (item->key >= key) {
- *pred_ptr = pred;
- *item_ptr = item;
- TRACE("l3", "find_pred_and_item: key found, returning pred %p and item %p", pred, item);
- return;
+ TRACE("l3", "find_pred: found pred %p item %p", pred, item);
+ if (pred_ptr != NULL) {
+ *pred_ptr = pred;
+ }
+ return item;
}
- assert(count++ < 18);
pred = item;
item = next;
- } while (1);
+ }
+
+ // <key> is not in <ll>.
+ if (pred_ptr != NULL) {
+ *pred_ptr = pred;
+ }
+ return NULL;
}
-int list_insert (list_t *list, node_t *item) {
- TRACE("l3", "list_insert: inserting %p (with key %llu)", item, item->key);
- node_t *pred, *next, *other = (node_t *)-1;
+// Fast find. Do not help unlink partially removed nodes and do not return the found item's predecessor.
+uint64_t ll_lookup (list_t *ll, uint64_t key) {
+ TRACE("l3", "ll_lookup: searching for key %p in ll %p", key, ll);
+ node_t *item = find_pred(NULL, ll, key, FALSE);
+
+ // If we found an <item> matching the <key> return its value.
+ return (item && item->key == key) ? item->value : DOES_NOT_EXIST;
+}
+
+// Insert the <key>, if it doesn't already exist in <ll>
+uint64_t ll_add (list_t *ll, uint64_t key, uint64_t value) {
+ TRACE("l3", "ll_add: inserting key %p value %p", key, value);
+ node_t *pred;
+ node_t *item = NULL;
do {
- if (other != (node_t *)-1) {
- TRACE("l3", "list_insert: failed to swap item into list; pred's next was changed to %p", other, 0);
- }
- find_pred_and_item(&pred, &next, list, item->key);
+ node_t *next = find_pred(&pred, ll, key, TRUE);
- // fail if item already exists in list
- if (next->key == item->key)
- {
- TRACE("l3", "list_insert: insert failed item with key already exists %p", next, 0);
- return 0;
+ // If a node matching <key> already exists in <ll>, return its value.
+ if (next != NULL && next->key == key) {
+ TRACE("l3", "ll_add: there is already an item %p (value %p) with the same key", next, next->value);
+ if (EXPECT_FALSE(item != NULL)) { nbd_free(item); }
+ return next->value;
}
+ TRACE("l3", "ll_add: attempting to insert item between %p and %p", pred, next);
+ if (EXPECT_TRUE(item == NULL)) { item = node_alloc(key, value); }
item->next = next;
- TRACE("l3", "list_insert: attempting to insert item between %p and %p", pred, next);
-
- } while ((other = __sync_val_compare_and_swap(&pred->next, next, item)) != next);
-
- TRACE("l3", "list_insert: insert was successful", 0, 0);
+ node_t *other = SYNC_CAS(&pred->next, next, item);
+ if (other == next) {
+ TRACE("l3", "ll_add: successfully inserted item %p", item, 0);
+ return DOES_NOT_EXIST; // success
+ }
+ TRACE("l3", "ll_add: failed to change pred's link: expected %p found %p", next, other);
- // success
- return 1;
+ } while (1);
}
-node_t *list_remove (list_t *list, int key) {
- node_t *pred, *item, *next;
-
- TRACE("l3", "list_remove: removing item with key %llu", key, 0);
- find_pred_and_item(&pred, &item, list, key);
- if (item->key != key)
- {
- TRACE("l3", "list_remove: remove failed, key does not exist in list", 0, 0);
- return NULL;
+uint64_t ll_remove (list_t *ll, uint64_t key) {
+ TRACE("l3", "ll_remove: removing item with key %p from ll %p", key, ll);
+ node_t *pred;
+ node_t *item = find_pred(&pred, ll, key, TRUE);
+ if (item == NULL || item->key != key) {
+ TRACE("l3", "ll_remove: remove failed, an item with a matching key does not exist in the ll", 0, 0);
+ return DOES_NOT_EXIST;
}
- // Mark <item> removed, must be atomic. If multiple threads try to remove the
- // same item only one of them should succeed
- next = item->next;
- node_t *other = (node_t *)-1;
- if (IS_MARKED(next) || (other = __sync_val_compare_and_swap(&item->next, next, PLACE_MARK(next))) != next) {
- if (other == (node_t *)-1) {
- TRACE("l3", "list_remove: retry; %p is already marked for removal (it's next pointer is %p)", item, next);
- } else {
- TRACE("l3", "list_remove: retry; failed to mark %p for removal; it's next pointer was %p, but changed to %p", next, other);
- }
- return list_remove(list, key); // retry
+ // Mark <item> removed. This must be atomic. If multiple threads try to remove the same item
+ // only one of them should succeed.
+ if (EXPECT_FALSE(IS_TAGGED(item->next))) {
+ TRACE("l3", "ll_remove: %p is already marked for removal by another thread", item, 0);
+ return DOES_NOT_EXIST;
}
-
- // Remove <item> from list
- TRACE("l3", "list_remove: link item's pred %p to it's successor %p", pred, next);
- if ((other = __sync_val_compare_and_swap(&pred->next, item, next)) != item) {
- TRACE("l3", "list_remove: link failed; pred's link changed from %p to %p", item, other);
-
- // make sure item gets unlinked before returning it
- node_t *d1, *d2;
- find_pred_and_item(&d1, &d2, list, key);
- } else {
- TRACE("l3", "list_remove: link succeeded; pred's link changed from %p to %p", item, next);
+ node_t *next = SYNC_FETCH_AND_OR(&item->next, TAG);
+ if (EXPECT_FALSE(IS_TAGGED(next))) {
+ TRACE("l3", "ll_remove: lost race -- %p is already marked for removal by another thread", item, 0);
+ return DOES_NOT_EXIST;
}
- return item;
+ uint64_t value = item->value;
+
+ // Unlink <item> from <ll>.
+ TRACE("l3", "ll_remove: link item's pred %p to it's successor %p", pred, next);
+ node_t *other;
+ if ((other = SYNC_CAS(&pred->next, item, next)) != item) {
+ TRACE("l3", "ll_remove: unlink failed; pred's link changed from %p to %p", item, other);
+ // By marking the item earlier, we logically removed it. It is safe to leave the item.
+ // Another thread will finish physically removing it from the ll.
+ return value;
+ }
+
+ // The thread that completes the unlink should free the memory.
+ nbd_defer_free(item);
+ return value;
}
-void list_print (list_t *list) {
+void ll_print (list_t *ll) {
node_t *item;
- item = list->head;
+ item = ll->head->next;
while (item) {
- printf("%d ", item->key);
+ printf("0x%llx ", item->key);
fflush(stdout);
item = item->next;
}
printf("\n");
}
-
-#ifdef MAKE_list_test
-#include <errno.h>
-#include <pthread.h>
-#include "runtime.h"
-
-static volatile int wait_;
-static long num_threads_;
-static list_t *list_;
-
-void *worker (void *arg) {
- int id = (int)(size_t)arg;
-
- unsigned int rand_seed = id+1;//rdtsc_l();
-
- // Wait for all the worker threads to be ready.
- __sync_fetch_and_add(&wait_, -1);
- do {} while (wait_);
- __asm__ __volatile__("lfence");
-
- int i;
- for (i = 0; i < NUM_ITERATIONS/num_threads_; ++i) {
- int n = rand_r(&rand_seed);
- int key = (n & 0xF) + 1;
- if (n & (1 << 8)) {
- node_t *item = list_node_alloc(key);
- int success = list_insert(list_, item);
- if (!success) {
- nbd_free(item);
- }
- } else {
- node_t *item = list_remove(list_, key);
- if (item) {
- nbd_defer_free(item);
- }
- }
-
- rcu_update();
- }
-
- return NULL;
-}
-
-int main (int argc, char **argv) {
- nbd_init();
- //lwt_set_trace_level("m0l0");
-
- char* program_name = argv[0];
- pthread_t thread[MAX_NUM_THREADS];
-
- if (argc > 2) {
- fprintf(stderr, "Usage: %s num_threads\n", program_name);
- return -1;
- }
-
- num_threads_ = 2;
- if (argc == 2)
- {
- errno = 0;
- num_threads_ = strtol(argv[1], NULL, 10);
- if (errno) {
- fprintf(stderr, "%s: Invalid argument for number of threads\n", program_name);
- return -1;
- }
- if (num_threads_ <= 0) {
- fprintf(stderr, "%s: Number of threads must be at least 1\n", program_name);
- return -1;
- }
- if (num_threads_ > MAX_NUM_THREADS) {
- fprintf(stderr, "%s: Number of threads cannot be more than %d\n", program_name, MAX_NUM_THREADS);
- return -1;
- }
- }
-
- list_ = list_alloc();
-
- struct timeval tv1, tv2;
- gettimeofday(&tv1, NULL);
-
- __asm__ __volatile__("sfence");
- wait_ = num_threads_;
-
- int i;
- for (i = 0; i < num_threads_; ++i) {
- int rc = nbd_thread_create(thread + i, i, worker, (void*)(size_t)i);
- if (rc != 0) { perror("pthread_create"); return rc; }
- }
-
- for (i = 0; i < num_threads_; ++i) {
- pthread_join(thread[i], NULL);
- }
-
- gettimeofday(&tv2, NULL);
- int ms = (int)(1000000*(tv2.tv_sec - tv1.tv_sec) + tv2.tv_usec - tv1.tv_usec) / 1000;
- printf("Th:%ld Time:%dms\n", num_threads_, ms);
- list_print(list_);
- lwt_dump("lwt.out");
-
- return 0;
-}
-#endif//list_test
projects / nbds / blobdiff