X-Git-Url: https://pd.if.org/git/?p=nbds;a=blobdiff_plain;f=struct%2Flist.c;h=29784a9dc61ba2f01286827e9b3e4cec2912b475;hp=28c15aa9da2f4e9643b0c1b89a421f4208faf9e6;hb=b21e1c182a2e469240d2b1cbbda37f2dfeb880d9;hpb=4a7804bd08c790fc3c4233312e4b485c3302fe02 diff --git a/struct/list.c b/struct/list.c index 28c15aa..29784a9 100644 --- a/struct/list.c +++ b/struct/list.c @@ -7,272 +7,187 @@ */ #include #include -#include #include "common.h" -#include "lwt.h" -#include "rcu.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); + } + + // is not in . + 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 matching the return its value. + return (item && item->key == key) ? item->value : DOES_NOT_EXIST; +} + +// Insert the , if it doesn't already exist in +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 already exists in , 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 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 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 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 from . + 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 -#include -#include "nbd.h" - -static volatile int wait_; -static long num_threads_; -static list_t *list_; - -void *worker (void *arg) -{ - int id = (int)(size_t)arg; - nbd_thread_init(id); - - 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 = pthread_create(thread + i, NULL, 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