ck_epoch: Collect from previous instance of epoch. Add torture test.

This typo lead to incorrect results. Added a read-mostly torture
test (follow on work is volatile interface for stack).

include/ck_epoch.h

@@ -203,13 +203,13 @@ ck_epoch_reclaim(struct ck_epoch_record *record)
 	 * the calling thread. No active reference should exist to
 	 * any object in the record's pending list.
 	 */
-	CK_STACK_FOREACH_SAFE(&record->pending[epoch], cursor, next) {
+	CK_STACK_FOREACH_SAFE(&record->pending[g_epoch], cursor, next) {
 		global->destroy(cursor);
 		record->n_pending--;
 		record->n_reclamations++;
 	}
 
-	ck_stack_init(&record->pending[epoch]);
+	ck_stack_init(&record->pending[g_epoch]);
 	record->epoch = g_epoch;
 	record->delta = 0;
 
@@ -273,9 +273,10 @@ ck_epoch_retire(struct ck_epoch_record *record, ck_stack_entry_t *entry)
 CK_CC_INLINE static void
 ck_epoch_free(struct ck_epoch_record *record, ck_stack_entry_t *entry)
 {
+	unsigned int epoch = ck_pr_load_uint(&record->epoch);
 	struct ck_epoch *global = record->global;
 
-	ck_stack_push_spnc(&record->pending[record->epoch], entry);
+	ck_stack_push_spnc(&record->pending[epoch], entry);
 	record->n_pending += 1;
 
 	if (record->n_pending > record->n_peak)

regressions/ck_epoch/validate/Makefile

@@ -1,9 +1,12 @@
 .PHONY: clean distribution
 
-OBJECTS=ck_stack
+OBJECTS=ck_stack ck_stack_read
 
 all: $(OBJECTS)
 
+ck_stack_read: ck_stack_read.c ../../../include/ck_stack.h ../../../include/ck_epoch.h
+	$(CC) $(CFLAGS) -o ck_stack_read ck_stack_read.c
+
 ck_stack: ck_stack.c ../../../include/ck_stack.h ../../../include/ck_epoch.h
 	$(CC) $(CFLAGS) -o ck_stack ck_stack.c
 

regressions/ck_epoch/validate/ck_stack.c

@@ -110,13 +110,13 @@ thread(void *unused CK_CC_UNUSED)
 	ck_pr_inc_uint(&e_barrier);
 	while (ck_pr_load_uint(&e_barrier) < n_threads);
 
-	fprintf(stderr, "Peak: %u (%2.2f%%)\nReclamations: %" PRIu64 "\n\n",
+	fprintf(stderr, "Peak: %u (%2.2f%%), %u pending\nReclamations: %" PRIu64 "\n\n",
 			record.n_peak,
 			(double)record.n_peak / PAIRS * 100,
+			record.n_pending,
 			record.n_reclamations);
 
 	ck_epoch_purge(&record);
-
 	ck_pr_inc_uint(&e_barrier);
 	while (ck_pr_load_uint(&e_barrier) < (n_threads << 1));
 

regressions/ck_epoch/validate/ck_stack_read.c

@@ -0,0 +1,220 @@
+/*
+ * Copyright 2010-2011 Samy Al Bahra.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <errno.h>
+#include <inttypes.h>
+#include <pthread.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <strings.h>
+#include <unistd.h>
+#include <sys/time.h>
+
+#include <ck_backoff.h>
+#include <ck_cc.h>
+#include <ck_pr.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <ck_epoch.h>
+#include <ck_stack.h>
+
+#include "../../common.h"
+
+static unsigned int threshold;
+static unsigned int n_threads;
+static unsigned int barrier;
+static unsigned int e_barrier;
+static unsigned int readers;
+
+#ifndef PAIRS
+#define PAIRS 5000000 
+#endif
+
+#ifndef ITERATE
+#define ITERATE 20
+#endif
+
+struct node {
+	unsigned int value;
+	ck_stack_entry_t stack_entry;
+};
+static ck_stack_t stack = CK_STACK_INITIALIZER;
+static ck_epoch_t stack_epoch;
+CK_STACK_CONTAINER(struct node, stack_entry, stack_container)
+static struct affinity a;
+
+static void *
+read_thread(void *unused CK_CC_UNUSED)
+{
+	unsigned int j;
+	ck_epoch_record_t record;
+	ck_stack_entry_t *cursor;
+	volatile ck_stack_entry_t *n;
+
+	ck_epoch_register(&stack_epoch, &record);
+
+	if (aff_iterate(&a)) {
+		perror("ERROR: failed to affine thread");
+		exit(EXIT_FAILURE);
+	}
+
+	ck_pr_inc_uint(&barrier);
+	while (ck_pr_load_uint(&barrier) < n_threads);
+
+	while (CK_STACK_ISEMPTY(&stack) == true) {
+		if (ck_pr_load_uint(&readers) != 0)
+			break;
+
+		ck_pr_stall();
+	}
+
+	j = 0;
+	for (;;) {
+		ck_epoch_read_begin(&record);
+		CK_STACK_FOREACH(&stack, cursor) {
+			n = cursor;
+			j++;
+		}
+		ck_epoch_end(&record);
+
+		if (j != 0 && ck_pr_load_uint(&readers) == 0)
+			ck_pr_store_uint(&readers, 1);
+
+		if (CK_STACK_ISEMPTY(&stack) == true &&
+		    ck_pr_load_uint(&e_barrier) != 0)
+			break;
+	}
+
+	ck_pr_inc_uint(&e_barrier);
+	while (ck_pr_load_uint(&e_barrier) < n_threads);
+
+	fprintf(stderr, "[R] Observed entries: %u\n", j);
+	return (NULL);
+}
+
+static void *
+thread(void *unused CK_CC_UNUSED)
+{
+	struct node **entry, *e;
+	unsigned int i, j;
+	ck_epoch_record_t record;
+	ck_stack_entry_t *s;
+
+	ck_epoch_register(&stack_epoch, &record);
+
+	if (aff_iterate(&a)) {
+		perror("ERROR: failed to affine thread");
+		exit(EXIT_FAILURE);
+	}
+
+	ck_pr_inc_uint(&barrier);
+	while (ck_pr_load_uint(&barrier) < n_threads);
+
+	entry = malloc(sizeof(struct node *) * PAIRS);
+	if (entry == NULL) {
+		fprintf(stderr, "Failed allocation.\n");
+		exit(EXIT_FAILURE);
+	}
+
+	for (j = 0; j < ITERATE; j++) {
+		for (i = 0; i < PAIRS; i++) {
+			entry[i] = malloc(sizeof(struct node));
+			if (entry == NULL) {
+				fprintf(stderr, "Failed individual allocation\n");
+				exit(EXIT_FAILURE);
+			}
+		}
+
+		for (i = 0; i < PAIRS; i++) {
+			ck_epoch_write_begin(&record);
+			ck_stack_push_upmc(&stack, &entry[i]->stack_entry);
+			ck_epoch_end(&record);
+		}
+
+		while (ck_pr_load_uint(&readers) == 0)
+			ck_pr_stall();
+
+		for (i = 0; i < PAIRS; i++) {
+			ck_epoch_write_begin(&record);
+			s = ck_stack_pop_upmc(&stack);
+			ck_epoch_end(&record);
+
+			e = stack_container(s);
+			ck_epoch_free(&record, &e->stack_entry);
+		}
+	}
+
+	ck_pr_inc_uint(&e_barrier);
+	while (ck_pr_load_uint(&e_barrier) < n_threads);
+
+	fprintf(stderr, "[W] Peak: %u (%2.2f%%)\n    Reclamations: %" PRIu64 "\n\n",
+			record.n_peak,
+			(double)record.n_peak / ((double)PAIRS * ITERATE) * 100,
+			record.n_reclamations);
+
+	return (NULL);
+}
+
+static void
+destructor(ck_stack_entry_t *p)
+{
+	struct node *e = stack_container(p);
+
+	free(e);
+	return;
+}
+
+int
+main(int argc, char *argv[])
+{
+	unsigned int i;
+	pthread_t *threads;
+
+	if (argc != 4) {
+		fprintf(stderr, "Usage: stack <threads> <threshold> <delta>\n");
+		exit(EXIT_FAILURE);
+	}
+
+	n_threads = atoi(argv[1]);
+	threshold = atoi(argv[2]);
+	a.delta = atoi(argv[3]);
+	a.request = 0;
+
+	threads = malloc(sizeof(pthread_t) * n_threads);
+
+	ck_epoch_init(&stack_epoch, threshold, destructor);
+
+	for (i = 0; i < n_threads - 1; i++) 
+		pthread_create(threads + i, NULL, read_thread, NULL);
+
+	pthread_create(threads + i, NULL, thread, NULL);
+
+	for (i = 0; i < n_threads; i++) 
+		pthread_join(threads[i], NULL);
+
+	return (0);
+}