test wfcqueue: add tests for queue state return value

with e.g. ./test_urcu_wfcq 2 2 10 -w

we can confirm that we see as many "enqueue to empty queue" as we see
"splice from non-empty queue", which confirms that the queue state
returned by enqueue is indeed sampled atomically with enqueue.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
CC: Lai Jiangshan <laijs@cn.fujitsu.com>

diff --git a/tests/test_urcu_wfcq.c b/tests/test_urcu_wfcq.c
index f90fc14baf52bc00229d9e9672e3ce4953d86f86..ccd5cf169436171baadd50d46ce261892764666b 100644 (file)
--- a/tests/test_urcu_wfcq.c
+++ b/tests/test_urcu_wfcq.c
@@ -75,7 +75,7 @@ enum test_sync {
 
 static enum test_sync test_sync;
 
-static volatile int test_go, test_stop;
+static volatile int test_go, test_stop_enqueue, test_stop_dequeue;
 
 static unsigned long rduration;
 
@@ -92,7 +92,8 @@ static inline void loop_sleep(unsigned long loops)
 
 static int verbose_mode;
 
-static int test_dequeue, test_splice;
+static int test_dequeue, test_splice, test_wait_empty;
+static int test_enqueue_stopped;
 
 #define printf_verbose(fmt, args...)           \
        do {                                    \
@@ -150,12 +151,12 @@ static void set_affinity(void)
  */
 static int test_duration_dequeue(void)
 {
-       return !test_stop;
+       return !test_stop_dequeue;
 }
 
 static int test_duration_enqueue(void)
 {
-       return !test_stop;
+       return !test_stop_enqueue;
 }
 
 static DEFINE_URCU_TLS(unsigned long long, nr_dequeues);
@@ -163,6 +164,8 @@ static DEFINE_URCU_TLS(unsigned long long, nr_enqueues);
 
 static DEFINE_URCU_TLS(unsigned long long, nr_successful_dequeues);
 static DEFINE_URCU_TLS(unsigned long long, nr_successful_enqueues);
+static DEFINE_URCU_TLS(unsigned long long, nr_empty_dest_enqueues);
+static DEFINE_URCU_TLS(unsigned long long, nr_splice);
 
 static unsigned int nr_enqueuers;
 static unsigned int nr_dequeuers;
@@ -173,6 +176,7 @@ static struct cds_wfcq_tail __attribute__((aligned(CAA_CACHE_LINE_SIZE))) tail;
 static void *thr_enqueuer(void *_count)
 {
        unsigned long long *count = _count;
+       bool was_nonempty;
 
        printf_verbose("thread_begin %s, thread id : %lx, tid %lu\n",
                        "enqueuer", (unsigned long) pthread_self(),
@@ -190,8 +194,10 @@ static void *thr_enqueuer(void *_count)
                if (!node)
                        goto fail;
                cds_wfcq_node_init(node);
-               cds_wfcq_enqueue(&head, &tail, node);
+               was_nonempty = cds_wfcq_enqueue(&head, &tail, node);
                URCU_TLS(nr_successful_enqueues)++;
+               if (!was_nonempty)
+                       URCU_TLS(nr_empty_dest_enqueues)++;
 
                if (caa_unlikely(wdelay))
                        loop_sleep(wdelay);
@@ -201,13 +207,18 @@ fail:
                        break;
        }
 
+       uatomic_inc(&test_enqueue_stopped);
        count[0] = URCU_TLS(nr_enqueues);
        count[1] = URCU_TLS(nr_successful_enqueues);
+       count[2] = URCU_TLS(nr_empty_dest_enqueues);
        printf_verbose("enqueuer thread_end, thread id : %lx, tid %lu, "
-                      "enqueues %llu successful_enqueues %llu\n",
+                      "enqueues %llu successful_enqueues %llu, "
+                      "empty_dest_enqueues %llu\n",
                       pthread_self(),
                        (unsigned long) gettid(),
-                      URCU_TLS(nr_enqueues), URCU_TLS(nr_successful_enqueues));
+                      URCU_TLS(nr_enqueues),
+                      URCU_TLS(nr_successful_enqueues),
+                      URCU_TLS(nr_empty_dest_enqueues));
        return ((void*)1);
 
 }
@@ -233,16 +244,33 @@ static void do_test_splice(enum test_sync sync)
        struct cds_wfcq_head tmp_head;
        struct cds_wfcq_tail tmp_tail;
        struct cds_wfcq_node *node, *n;
+       enum cds_wfcq_ret ret;
 
        cds_wfcq_init(&tmp_head, &tmp_tail);
 
        if (sync == TEST_SYNC_MUTEX)
-               cds_wfcq_splice_blocking(&tmp_head, &tmp_tail,
+               ret = cds_wfcq_splice_blocking(&tmp_head, &tmp_tail,
                        &head, &tail);
        else
-               __cds_wfcq_splice_blocking(&tmp_head, &tmp_tail,
+               ret = __cds_wfcq_splice_blocking(&tmp_head, &tmp_tail,
                        &head, &tail);
 
+       switch (ret) {
+       case CDS_WFCQ_RET_WOULDBLOCK:
+               assert(0);      /* blocking call */
+               break;
+       case CDS_WFCQ_RET_DEST_EMPTY:
+               URCU_TLS(nr_splice)++;
+               /* ok */
+               break;
+       case CDS_WFCQ_RET_DEST_NON_EMPTY:
+               assert(0);      /* entirely unexpected */
+               break;
+       case CDS_WFCQ_RET_SRC_EMPTY:
+               /* ok, we could even skip iteration on dest if we wanted */
+               break;
+       }
+
        __cds_wfcq_for_each_blocking_safe(&tmp_head, &tmp_tail, node, n) {
                free(node);
                URCU_TLS(nr_successful_dequeues)++;
@@ -286,12 +314,15 @@ static void *thr_dequeuer(void *_count)
        }
 
        printf_verbose("dequeuer thread_end, thread id : %lx, tid %lu, "
-                      "dequeues %llu, successful_dequeues %llu\n",
+                      "dequeues %llu, successful_dequeues %llu, "
+                      "nr_splice %llu\n",
                       pthread_self(),
                        (unsigned long) gettid(),
-                      URCU_TLS(nr_dequeues), URCU_TLS(nr_successful_dequeues));
+                      URCU_TLS(nr_dequeues), URCU_TLS(nr_successful_dequeues),
+                      URCU_TLS(nr_splice));
        count[0] = URCU_TLS(nr_dequeues);
        count[1] = URCU_TLS(nr_successful_dequeues);
+       count[2] = URCU_TLS(nr_splice);
        return ((void*)2);
 }
 
@@ -320,6 +351,7 @@ static void show_usage(int argc, char **argv)
        printf(" [-M] (use mutex external synchronization)");
        printf(" [-0] (use no external synchronization)");
        printf("      Note: default: mutex external synchronization used.");
+       printf(" [-w] Wait for dequeuer to empty queue");
        printf("\n");
 }
 
@@ -331,9 +363,11 @@ int main(int argc, char **argv)
        unsigned long long *count_enqueuer, *count_dequeuer;
        unsigned long long tot_enqueues = 0, tot_dequeues = 0;
        unsigned long long tot_successful_enqueues = 0,
-                          tot_successful_dequeues = 0;
+                          tot_successful_dequeues = 0,
+                          tot_empty_dest_enqueues = 0,
+                          tot_splice = 0;
        unsigned long long end_dequeues = 0;
-       int i, a;
+       int i, a, retval = 0;
 
        if (argc < 4) {
                show_usage(argc, argv);
@@ -401,6 +435,9 @@ int main(int argc, char **argv)
                case '0':
                        test_sync = TEST_SYNC_NONE;
                        break;
+               case 'w':
+                       test_wait_empty = 1;
+                       break;
                }
        }
 
@@ -419,6 +456,8 @@ int main(int argc, char **argv)
                printf_verbose("External sync: mutex.\n");
        else
                printf_verbose("External sync: none.\n");
+       if (test_wait_empty)
+               printf_verbose("Wait for dequeuers to empty queue.\n");
        printf_verbose("Writer delay : %lu loops.\n", rduration);
        printf_verbose("Reader duration : %lu loops.\n", wdelay);
        printf_verbose("thread %-6s, thread id : %lx, tid %lu\n",
@@ -427,21 +466,21 @@ int main(int argc, char **argv)
 
        tid_enqueuer = malloc(sizeof(*tid_enqueuer) * nr_enqueuers);
        tid_dequeuer = malloc(sizeof(*tid_dequeuer) * nr_dequeuers);
-       count_enqueuer = malloc(2 * sizeof(*count_enqueuer) * nr_enqueuers);
-       count_dequeuer = malloc(2 * sizeof(*count_dequeuer) * nr_dequeuers);
+       count_enqueuer = malloc(3 * sizeof(*count_enqueuer) * nr_enqueuers);
+       count_dequeuer = malloc(3 * sizeof(*count_dequeuer) * nr_dequeuers);
        cds_wfcq_init(&head, &tail);
 
        next_aff = 0;
 
        for (i = 0; i < nr_enqueuers; i++) {
                err = pthread_create(&tid_enqueuer[i], NULL, thr_enqueuer,
-                                    &count_enqueuer[2 * i]);
+                                    &count_enqueuer[3 * i]);
                if (err != 0)
                        exit(1);
        }
        for (i = 0; i < nr_dequeuers; i++) {
                err = pthread_create(&tid_dequeuer[i], NULL, thr_dequeuer,
-                                    &count_dequeuer[2 * i]);
+                                    &count_dequeuer[3 * i]);
                if (err != 0)
                        exit(1);
        }
@@ -456,21 +495,34 @@ int main(int argc, char **argv)
                        write (1, ".", 1);
        }
 
-       test_stop = 1;
+       test_stop_enqueue = 1;
+
+       if (test_wait_empty) {
+               while (nr_enqueuers != uatomic_read(&test_enqueue_stopped)) {
+                       sleep(1);
+               }
+               while (!cds_wfcq_empty(&head, &tail)) {
+                       sleep(1);
+               }
+       }
+
+       test_stop_dequeue = 1;
 
        for (i = 0; i < nr_enqueuers; i++) {
                err = pthread_join(tid_enqueuer[i], &tret);
                if (err != 0)
                        exit(1);
-               tot_enqueues += count_enqueuer[2 * i];
-               tot_successful_enqueues += count_enqueuer[2 * i + 1];
+               tot_enqueues += count_enqueuer[3 * i];
+               tot_successful_enqueues += count_enqueuer[3 * i + 1];
+               tot_empty_dest_enqueues += count_enqueuer[3 * i + 2];
        }
        for (i = 0; i < nr_dequeuers; i++) {
                err = pthread_join(tid_dequeuer[i], &tret);
                if (err != 0)
                        exit(1);
-               tot_dequeues += count_dequeuer[2 * i];
-               tot_successful_dequeues += count_dequeuer[2 * i + 1];
+               tot_dequeues += count_dequeuer[3 * i];
+               tot_successful_dequeues += count_dequeuer[3 * i + 1];
+               tot_splice += count_dequeuer[3 * i + 2];
        }
        
        test_end(&end_dequeues);
@@ -478,27 +530,50 @@ int main(int argc, char **argv)
        printf_verbose("total number of enqueues : %llu, dequeues %llu\n",
                       tot_enqueues, tot_dequeues);
        printf_verbose("total number of successful enqueues : %llu, "
-                      "successful dequeues %llu\n",
-                      tot_successful_enqueues, tot_successful_dequeues);
+                      "enqueues to empty dest : %llu, "
+                      "successful dequeues %llu, ",
+                      "splice : %llu\n",
+                      tot_successful_enqueues,
+                      tot_empty_dest_enqueues,
+                      tot_successful_dequeues,
+                      tot_splice);
        printf("SUMMARY %-25s testdur %4lu nr_enqueuers %3u wdelay %6lu "
                "nr_dequeuers %3u "
                "rdur %6lu nr_enqueues %12llu nr_dequeues %12llu "
-               "successful enqueues %12llu successful dequeues %12llu "
+               "successful enqueues %12llu enqueues to empty dest %12llu "
+               "successful dequeues %12llu splice %12llu "
                "end_dequeues %llu nr_ops %12llu\n",
                argv[0], duration, nr_enqueuers, wdelay,
                nr_dequeuers, rduration, tot_enqueues, tot_dequeues,
                tot_successful_enqueues,
-               tot_successful_dequeues, end_dequeues,
+               tot_empty_dest_enqueues,
+               tot_successful_dequeues, tot_splice, end_dequeues,
                tot_enqueues + tot_dequeues);
-       if (tot_successful_enqueues != tot_successful_dequeues + end_dequeues)
+
+       if (tot_successful_enqueues != tot_successful_dequeues + end_dequeues) {
                printf("WARNING! Discrepancy between nr succ. enqueues %llu vs "
                       "succ. dequeues + end dequeues %llu.\n",
                       tot_successful_enqueues,
                       tot_successful_dequeues + end_dequeues);
+               retval = 1;
+       }
 
+       /*
+        * If only using splice to dequeue, the enqueuer should see
+        * exactly as many empty queues than the number of non-empty
+        * src splice.
+        */
+       if (test_wait_empty && test_splice && !test_dequeue
+                       && tot_empty_dest_enqueues != tot_splice) {
+               printf("WARNING! Discrepancy between empty enqueue (%llu) and "
+                       "number of non-empty splice (%llu)\n",
+                       tot_empty_dest_enqueues,
+                       tot_splice);
+               retval = 1;
+       }
        free(count_enqueuer);
        free(count_dequeuer);
        free(tid_enqueuer);
        free(tid_dequeuer);
-       return 0;
+       return retval;
 }