rcu: introduce RCU-enabled QLIST

Add RCU-enabled variants on the existing bsd DQ facility. Each
operation has the same interface as the existing (non-RCU)
version. Also, each operation is implemented as macro.

Using the RCU-enabled QLIST, existing QLIST users will be able to
convert to RCU without using a different list interface.

Signed-off-by: Mike Day <ncmike@ncultra.org>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 306 insertions, 0 deletions

diff --git a/tests/test-rcu-list.c b/tests/test-rcu-list.c
new file mode 100644
index 0000000000..46b5e263e5
--- /dev/null
+++ b/tests/test-rcu-list.c
@@ -0,0 +1,306 @@
+/*
+ * rcuq_test.c
+ *
+ * usage: rcuq_test <readers> <duration>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (c) 2013 Mike D. Day, IBM Corporation.
+ */
+
+#include <glib.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include "qemu/atomic.h"
+#include "qemu/rcu.h"
+#include "qemu/compiler.h"
+#include "qemu/osdep.h"
+#include "qemu/thread.h"
+#include "qemu/rcu_queue.h"
+
+/*
+ * Test variables.
+ */
+
+long long n_reads = 0LL;
+long long n_updates = 0LL;
+long long n_reclaims = 0LL;
+long long n_nodes_removed = 0LL;
+long long n_nodes = 0LL;
+int g_test_in_charge = 0;
+
+int nthreadsrunning;
+
+char argsbuf[64];
+
+#define GOFLAG_INIT 0
+#define GOFLAG_RUN  1
+#define GOFLAG_STOP 2
+
+static volatile int goflag = GOFLAG_INIT;
+
+#define RCU_READ_RUN 1000
+#define RCU_UPDATE_RUN 10
+#define NR_THREADS 100
+#define RCU_Q_LEN 100
+
+static QemuThread threads[NR_THREADS];
+static struct rcu_reader_data *data[NR_THREADS];
+static int n_threads;
+
+static int select_random_el(int max)
+{
+    return (rand() % max);
+}
+
+
+static void create_thread(void *(*func)(void *))
+{
+    if (n_threads >= NR_THREADS) {
+        fprintf(stderr, "Thread limit of %d exceeded!\n", NR_THREADS);
+        exit(-1);
+    }
+    qemu_thread_create(&threads[n_threads], "test", func, &data[n_threads],
+                       QEMU_THREAD_JOINABLE);
+    n_threads++;
+}
+
+static void wait_all_threads(void)
+{
+    int i;
+
+    for (i = 0; i < n_threads; i++) {
+        qemu_thread_join(&threads[i]);
+    }
+    n_threads = 0;
+}
+
+
+struct list_element {
+    QLIST_ENTRY(list_element) entry;
+    struct rcu_head rcu;
+    long long val;
+};
+
+static void reclaim_list_el(struct rcu_head *prcu)
+{
+    struct list_element *el = container_of(prcu, struct list_element, rcu);
+    g_free(el);
+    atomic_add(&n_reclaims, 1);
+}
+
+static QLIST_HEAD(q_list_head, list_element) Q_list_head;
+
+static void *rcu_q_reader(void *arg)
+{
+    long long j, n_reads_local = 0;
+    struct list_element *el;
+
+    *(struct rcu_reader_data **)arg = &rcu_reader;
+    atomic_inc(&nthreadsrunning);
+    while (goflag == GOFLAG_INIT) {
+        g_usleep(1000);
+    }
+
+    while (goflag == GOFLAG_RUN) {
+        rcu_read_lock();
+        QLIST_FOREACH_RCU(el, &Q_list_head, entry) {
+            j = atomic_read(&el->val);
+            (void)j;
+            n_reads_local++;
+            if (goflag == GOFLAG_STOP) {
+                break;
+            }
+        }
+        rcu_read_unlock();
+
+        g_usleep(100);
+    }
+    atomic_add(&n_reads, n_reads_local);
+    return NULL;
+}
+
+
+static void *rcu_q_updater(void *arg)
+{
+    int j, target_el;
+    long long n_updates_local = 0;
+    long long n_removed_local = 0;
+    struct list_element *el, *prev_el;
+
+    *(struct rcu_reader_data **)arg = &rcu_reader;
+    atomic_inc(&nthreadsrunning);
+    while (goflag == GOFLAG_INIT) {
+        g_usleep(1000);
+    }
+
+    while (goflag == GOFLAG_RUN) {
+        target_el = select_random_el(RCU_Q_LEN);
+        j = 0;
+        /* FOREACH_RCU could work here but let's use both macros */
+        QLIST_FOREACH_SAFE_RCU(prev_el, &Q_list_head, entry, el) {
+            j++;
+            if (target_el == j) {
+                QLIST_REMOVE_RCU(prev_el, entry);
+                /* may be more than one updater in the future */
+                call_rcu1(&prev_el->rcu, reclaim_list_el);
+                n_removed_local++;
+                break;
+            }
+        }
+        if (goflag == GOFLAG_STOP) {
+            break;
+        }
+        target_el = select_random_el(RCU_Q_LEN);
+        j = 0;
+        QLIST_FOREACH_RCU(el, &Q_list_head, entry) {
+            j++;
+            if (target_el == j) {
+                prev_el = g_new(struct list_element, 1);
+                atomic_add(&n_nodes, 1);
+                prev_el->val = atomic_read(&n_nodes);
+                QLIST_INSERT_BEFORE_RCU(el, prev_el, entry);
+                break;
+            }
+        }
+
+        n_updates_local += 2;
+        synchronize_rcu();
+    }
+    synchronize_rcu();
+    atomic_add(&n_updates, n_updates_local);
+    atomic_add(&n_nodes_removed, n_removed_local);
+    return NULL;
+}
+
+static void rcu_qtest_init(void)
+{
+    struct list_element *new_el;
+    int i;
+    nthreadsrunning = 0;
+    srand(time(0));
+    for (i = 0; i < RCU_Q_LEN; i++) {
+        new_el = g_new(struct list_element, 1);
+        new_el->val = i;
+        QLIST_INSERT_HEAD_RCU(&Q_list_head, new_el, entry);
+    }
+    atomic_add(&n_nodes, RCU_Q_LEN);
+}
+
+static void rcu_qtest_run(int duration, int nreaders)
+{
+    int nthreads = nreaders + 1;
+    while (atomic_read(&nthreadsrunning) < nthreads) {
+        g_usleep(1000);
+    }
+
+    goflag = GOFLAG_RUN;
+    sleep(duration);
+    goflag = GOFLAG_STOP;
+    wait_all_threads();
+}
+
+
+static void rcu_qtest(const char *test, int duration, int nreaders)
+{
+    int i;
+    long long n_removed_local = 0;
+
+    struct list_element *el, *prev_el;
+
+    rcu_qtest_init();
+    for (i = 0; i < nreaders; i++) {
+        create_thread(rcu_q_reader);
+    }
+    create_thread(rcu_q_updater);
+    rcu_qtest_run(duration, nreaders);
+
+    QLIST_FOREACH_SAFE_RCU(prev_el, &Q_list_head, entry, el) {
+        QLIST_REMOVE_RCU(prev_el, entry);
+        call_rcu1(&prev_el->rcu, reclaim_list_el);
+        n_removed_local++;
+    }
+    atomic_add(&n_nodes_removed, n_removed_local);
+    synchronize_rcu();
+    while (n_nodes_removed > n_reclaims) {
+        g_usleep(100);
+        synchronize_rcu();
+    }
+    if (g_test_in_charge) {
+        g_assert_cmpint(n_nodes_removed, ==, n_reclaims);
+    } else {
+        printf("%s: %d readers; 1 updater; nodes read: "  \
+               "%lld, nodes removed: %lld; nodes reclaimed: %lld\n",
+               test, nthreadsrunning - 1, n_reads, n_nodes_removed, n_reclaims);
+        exit(0);
+    }
+}
+
+static void usage(int argc, char *argv[])
+{
+    fprintf(stderr, "Usage: %s duration nreaders\n", argv[0]);
+    exit(-1);
+}
+
+static int gtest_seconds;
+
+static void gtest_rcuq_one(void)
+{
+    rcu_qtest("rcuqtest", gtest_seconds / 4, 1);
+}
+
+static void gtest_rcuq_few(void)
+{
+    rcu_qtest("rcuqtest", gtest_seconds / 4, 5);
+}
+
+static void gtest_rcuq_many(void)
+{
+    rcu_qtest("rcuqtest", gtest_seconds / 2, 20);
+}
+
+
+int main(int argc, char *argv[])
+{
+    int duration = 0, readers = 0;
+
+    if (argc >= 2) {
+        if (argv[1][0] == '-') {
+            g_test_init(&argc, &argv, NULL);
+            if (g_test_quick()) {
+                gtest_seconds = 4;
+            } else {
+                gtest_seconds = 20;
+            }
+            g_test_add_func("/rcu/qlist/single-threaded", gtest_rcuq_one);
+            g_test_add_func("/rcu/qlist/short-few", gtest_rcuq_few);
+            g_test_add_func("/rcu/qlist/long-many", gtest_rcuq_many);
+            g_test_in_charge = 1;
+            return g_test_run();
+        }
+        duration = strtoul(argv[1], NULL, 0);
+    }
+    if (argc >= 3) {
+        readers = strtoul(argv[2], NULL, 0);
+    }
+    if (duration && readers) {
+        rcu_qtest(argv[0], duration, readers);
+        return 0;
+    }
+
+    usage(argc, argv);
+    return -1;
+}