Add a spinlock type.

Useful for situations where we need to repeatedly trylock, not useful
for cases where we need to lock (due to spinning).

Add a variant of sync_test to test it (with the same tests we run for
gpr_mu).

Add a benchmark to bm_closure to demonstrate single threaded performance.

2 files changed, 165 insertions, 0 deletions

diff --git a/test/core/support/BUILD b/test/core/support/BUILD
index dfe952eb37..08cee1441b 100644
--- a/test/core/support/BUILD
+++ b/test/core/support/BUILD
@@ -119,6 +119,13 @@ cc_test(
 )
 
 cc_test(
+    name = "spinlock_test",
+    srcs = ["spinlock_test.c"],
+    deps = ["//:gpr", "//test/core/util:gpr_test_util"],
+    copts = ['-std=c99']
+)
+
+cc_test(
     name = "sync_test",
     srcs = ["sync_test.c"],
     deps = ["//:gpr", "//test/core/util:gpr_test_util"],
diff --git a/test/core/support/spinlock_test.c b/test/core/support/spinlock_test.c
new file mode 100644
index 0000000000..20b402a705
--- /dev/null
+++ b/test/core/support/spinlock_test.c
@@ -0,0 +1,158 @@
+/*
+ *
+ * Copyright 2017, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * 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.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT
+ * OWNER 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.
+ *
+ */
+
+/* Test of gpr synchronization support. */
+
+#include "src/core/lib/support/spinlock.h"
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/sync.h>
+#include <grpc/support/thd.h>
+#include <grpc/support/time.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include "test/core/util/test_config.h"
+
+/* ------------------------------------------------- */
+/* Tests for gpr_spinlock. */
+struct test {
+  int thread_count; /* number of threads */
+  gpr_thd_id *threads;
+
+  int64_t iterations; /* number of iterations per thread */
+  int64_t counter;
+  int incr_step; /* how much to increment/decrement refcount each time */
+
+  gpr_spinlock mu; /* protects iterations, counter */
+};
+
+/* Return pointer to a new struct test. */
+static struct test *test_new(int threads, int64_t iterations, int incr_step) {
+  struct test *m = gpr_malloc(sizeof(*m));
+  m->thread_count = threads;
+  m->threads = gpr_malloc(sizeof(*m->threads) * (size_t)threads);
+  m->iterations = iterations;
+  m->counter = 0;
+  m->thread_count = 0;
+  m->incr_step = incr_step;
+  m->mu = GPR_SPINLOCK_INITIALIZER;
+  return m;
+}
+
+/* Return pointer to a new struct test. */
+static void test_destroy(struct test *m) { gpr_free(m); }
+
+/* Create m->threads threads, each running (*body)(m) */
+static void test_create_threads(struct test *m, void (*body)(void *arg)) {
+  int i;
+  for (i = 0; i != m->thread_count; i++) {
+    gpr_thd_options opt = gpr_thd_options_default();
+    gpr_thd_options_set_joinable(&opt);
+    GPR_ASSERT(gpr_thd_new(&m->threads[i], body, m, &opt));
+  }
+}
+
+/* Wait until all threads report done. */
+static void test_wait(struct test *m) {
+  int i;
+  for (i = 0; i != m->thread_count; i++) {
+    gpr_thd_join(m->threads[i]);
+  }
+}
+
+/* Test several threads running (*body)(struct test *m) for increasing settings
+   of m->iterations, until about timeout_s to 2*timeout_s seconds have elapsed.
+   If extra!=NULL, run (*extra)(m) in an additional thread.
+   incr_step controls by how much m->refcount should be incremented/decremented
+   (if at all) each time in the tests.
+   */
+static void test(const char *name, void (*body)(void *m), int timeout_s,
+                 int incr_step) {
+  int64_t iterations = 1024;
+  struct test *m;
+  gpr_timespec start = gpr_now(GPR_CLOCK_REALTIME);
+  gpr_timespec time_taken;
+  gpr_timespec deadline = gpr_time_add(
+      start, gpr_time_from_micros((int64_t)timeout_s * 1000000, GPR_TIMESPAN));
+  fprintf(stderr, "%s:", name);
+  while (gpr_time_cmp(gpr_now(GPR_CLOCK_REALTIME), deadline) < 0) {
+    iterations <<= 1;
+    fprintf(stderr, " %ld", (long)iterations);
+    m = test_new(10, iterations, incr_step);
+    test_create_threads(m, body);
+    test_wait(m);
+    if (m->counter != m->thread_count * m->iterations * m->incr_step) {
+      fprintf(stderr, "counter %ld  threads %d  iterations %ld\n",
+              (long)m->counter, m->thread_count, (long)m->iterations);
+      GPR_ASSERT(0);
+    }
+    test_destroy(m);
+  }
+  time_taken = gpr_time_sub(gpr_now(GPR_CLOCK_REALTIME), start);
+  fprintf(stderr, " done %lld.%09d s\n", (long long)time_taken.tv_sec,
+          (int)time_taken.tv_nsec);
+}
+
+/* Increment m->counter on each iteration; then mark thread as done.  */
+static void inc(void *v /*=m*/) {
+  struct test *m = v;
+  int64_t i;
+  for (i = 0; i != m->iterations; i++) {
+    gpr_spinlock_lock(&m->mu);
+    m->counter++;
+    gpr_spinlock_unlock(&m->mu);
+  }
+}
+
+/* Increment m->counter under lock acquired with trylock, m->iterations times;
+   then mark thread as done.  */
+static void inctry(void *v /*=m*/) {
+  struct test *m = v;
+  int64_t i;
+  for (i = 0; i != m->iterations;) {
+    if (gpr_spinlock_trylock(&m->mu)) {
+      m->counter++;
+      gpr_spinlock_unlock(&m->mu);
+      i++;
+    }
+  }
+}
+
+/* ------------------------------------------------- */
+
+int main(int argc, char *argv[]) {
+  grpc_test_init(argc, argv);
+  test("spinlock", &inc, 1, 1);
+  test("spinlock try", &inctry, 1, 1);
+  return 0;
+}