Implement pthread_rwlock functions for NaCl newlib

tests/threads/rwlock_test.c

Index: tests/threads/rwlock_test.c
diff --git a/tests/threads/rwlock_test.c b/tests/threads/rwlock_test.c
new file mode 100644
index 0000000000000000000000000000000000000000..a92cc1ed049caedcd0eb23febd8fac94adfa0b5b
--- /dev/null
+++ b/tests/threads/rwlock_test.c
@@ -0,0 +1,341 @@
+/*
+ * Copyright 2015 The Native Client Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include <errno.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <time.h>
+
+#include "native_client/src/include/nacl_assert.h"
+
+pthread_rwlock_t g_rwlock;
+volatile int g_thread_has_lock = 0;
+volatile int g_thread_should_acquire_lock = 0;
+volatile int g_thread_should_release_lock = 0;
+
+typedef enum {
+  READ_LOCK = 1,
+  WRITE_LOCK = 2,
+} lock_type;
+
+void *locking_thread(void *unused) {
+  int rc;
+  for (;;) {
+    while (!g_thread_should_acquire_lock) { /* Spin. */ }
+
+    ASSERT_EQ(g_thread_has_lock, 0);
+    if (g_thread_should_acquire_lock == WRITE_LOCK)
+      rc = pthread_rwlock_wrlock(&g_rwlock);
+    else
+      rc = pthread_rwlock_rdlock(&g_rwlock);
+    ASSERT_EQ(rc, 0);
+    __sync_fetch_and_add(&g_thread_has_lock, 1);
+
+    while (!g_thread_should_release_lock) { /* Spin. */ }
+
+    ASSERT_EQ(g_thread_has_lock, 1);
+    rc = pthread_rwlock_unlock(&g_rwlock);
+    ASSERT_EQ(rc, 0);
+    __sync_fetch_and_sub(&g_thread_has_lock, 1);
+  }
+
+  return NULL;
+}
+
+
+void tell_thread_to_acquire_lock(lock_type lock_type) {
+  fprintf(stderr, "Thread acquiring lock: %s\n",
+      lock_type == WRITE_LOCK ? "WRITE" : "READ");
+
+  ASSERT_EQ(g_thread_has_lock, 0);
+  ASSERT_EQ(g_thread_should_acquire_lock, 0);
+  __sync_fetch_and_add(&g_thread_should_acquire_lock, lock_type);
+
+  while (!g_thread_has_lock) { /* Spin. */ }
+
+  __sync_fetch_and_sub(&g_thread_should_acquire_lock, lock_type);
+  ASSERT_EQ(g_thread_should_acquire_lock, 0);
+
+  fprintf(stderr, "Thread acquired lock.\n");
+}
+
+void tell_thread_to_release_lock(void) {
+  fprintf(stderr, "Thread releasing lock.\n");
+
+  ASSERT_EQ(g_thread_has_lock, 1);
+  ASSERT_EQ(g_thread_should_release_lock, 0);
+  __sync_fetch_and_add(&g_thread_should_release_lock, 1);
+
+  while (g_thread_has_lock) { /* Spin. */ }
+
+  __sync_fetch_and_sub(&g_thread_should_release_lock, 1);
+  ASSERT_EQ(g_thread_should_release_lock, 0);
+
+  fprintf(stderr, "Thread released lock.\n");
+}
+
+void test_reader_timedwait(void) {
+  fprintf(stderr, "test_reader_timedwait\n");
+  tell_thread_to_acquire_lock(WRITE_LOCK);
+
+  struct timespec t = { 0, 0 };
+  int rc = pthread_rwlock_timedrdlock(&g_rwlock, &t);
+  ASSERT_EQ(rc, ETIMEDOUT);
+
+  tell_thread_to_release_lock();
+}
+
+void test_writer_timedwait(void) {
+  fprintf(stderr, "test_writer_timedwait\n");
+  tell_thread_to_acquire_lock(READ_LOCK);
+
+  struct timespec t = { 0, 0 };
+  int rc = pthread_rwlock_timedwrlock(&g_rwlock, &t);
+  ASSERT_EQ(rc, ETIMEDOUT);
+
+  tell_thread_to_release_lock();
+}
+
+void test_multiple_writers(void) {
+  fprintf(stderr, "test_multiple_writers\n");
+  tell_thread_to_acquire_lock(WRITE_LOCK);
+
+  /*
+   * Attempt to acquire second write lock should fail.
+   */
+  int rc = pthread_rwlock_trywrlock(&g_rwlock);
+  ASSERT_EQ(rc, EBUSY);
+
+  tell_thread_to_release_lock();
+}
+
+void test_recursive_reader(void) {
+  /*
+   * Test that an rdlock can be recursively acquired even when there
+   * is a waiting writer.
+   */
+  int rc = pthread_rwlock_rdlock(&g_rwlock);
+  ASSERT_EQ(rc, 0);
+
+  /*
+   * Tell the locking thread to attempt to acquire the write lock.
+   * This should fail and block until all readers are unlocked.
+   */
+  ASSERT_EQ(g_thread_has_lock, 0);
+  ASSERT_EQ(g_thread_should_acquire_lock, 0);
+  __sync_fetch_and_add(&g_thread_should_acquire_lock, WRITE_LOCK);
+
+  /*
+   * Sleep for 10ms
+   */
+  rc = usleep(10 * 1000);
+  ASSERT_EQ(rc, 0);
+  ASSERT_EQ(g_thread_has_lock, 0);
+
+  /*
+   * Now make sure the waiting writer doesn't block the recursive acquisition
+   * of the rdlock (using both tryrdlock and rdlock).
+   */
+  rc = pthread_rwlock_tryrdlock(&g_rwlock);
+  ASSERT_EQ(rc, 0);
+  rc = pthread_rwlock_unlock(&g_rwlock);
+  ASSERT_EQ(rc, 0);
+  ASSERT_EQ(g_thread_has_lock, 0);
+  rc = pthread_rwlock_rdlock(&g_rwlock);
+  ASSERT_EQ(rc, 0);
+  rc = pthread_rwlock_unlock(&g_rwlock);
+  ASSERT_EQ(rc, 0);
+  ASSERT_EQ(g_thread_has_lock, 0);
+
+  /*
+   * Finally unlock the rdlock which should allow the secondary thread
+   * to acquire the wrlock
+   */
+  rc = pthread_rwlock_unlock(&g_rwlock);
+  ASSERT_EQ(rc, 0);
+  while (!g_thread_has_lock) { /* Spin. */ }
+  __sync_fetch_and_sub(&g_thread_should_acquire_lock, WRITE_LOCK);
+  ASSERT_EQ(g_thread_should_acquire_lock, 0);
+
+  tell_thread_to_release_lock();
+}
+
+void test_multiple_readers(void) {
+  fprintf(stderr, "test_multiple_readers\n");
+  tell_thread_to_acquire_lock(READ_LOCK);
+
+  /*
+   * Now attempt to acquire the lock on the main thread.
+   * Since they are both readers this should succeed.
+   * Try with tryrdlock, rdlock and timedrdlock.
+   */
+  int rc = pthread_rwlock_tryrdlock(&g_rwlock);
+  ASSERT_EQ(rc, 0);
+  rc = pthread_rwlock_unlock(&g_rwlock);
+  ASSERT_EQ(rc, 0);
+
+  struct timespec t = { 0, 0 };
+  rc = pthread_rwlock_timedrdlock(&g_rwlock, &t);
+  ASSERT_EQ(rc, 0);
+  rc = pthread_rwlock_unlock(&g_rwlock);
+  ASSERT_EQ(rc, 0);
+
+  rc = pthread_rwlock_rdlock(&g_rwlock);
+  ASSERT_EQ(rc, 0);
+  rc = pthread_rwlock_unlock(&g_rwlock);
+  ASSERT_EQ(rc, 0);
+
+  tell_thread_to_release_lock();
+}
+
+void *read_lock_thread(void *unused) {
+  fprintf(stderr, "%lx: waiting for read lock\n", (long)pthread_self());
+  int rc = pthread_rwlock_rdlock(&g_rwlock);
+  fprintf(stderr, "%lx: read lock acquired\n", (long)pthread_self());
+  ASSERT_EQ(rc, 0);
+  rc = pthread_rwlock_unlock(&g_rwlock);
+  ASSERT_EQ(rc, 0);
+  fprintf(stderr, "%lx: thread done\n", (long)pthread_self());
+  return NULL;
+}
+
+/*
+ * Number of milliseconds delay before we assume that newly created threads
+ * (running read_lock_thread) are blocked on lock acquisition.
+ */
+#define THREAD_START_DELAY_MS 20
+
+/*
+ * Test that multiple readers are woken up when the write lock
+ * is released.
+ */
+void test_multiple_reader_wakeup(void) {
+  /*
+   * First, acquire the write lock so that all readers
+   * will be blocked.
+   */
+  fprintf(stderr, "test_multiple_reader_wakeup\n");
+  int rc;
+  rc = pthread_rwlock_wrlock(&g_rwlock);
+  ASSERT_EQ(rc, 0);
+
+  /*
+   * Now start two new threads that will both wait on a read lock.
+   */
+  pthread_t thread1;
+  rc = pthread_create(&thread1, NULL, read_lock_thread, NULL);
+  ASSERT_EQ(rc, 0);
+
+  pthread_t thread2;
+  rc = pthread_create(&thread2, NULL, read_lock_thread, NULL);
+  ASSERT_EQ(rc, 0);
+
+  /*
+   * We now need to wait until both threads are waiting on the read lock.
+   * However, we have no way to determine this as we do not record the number
+   * of waiting readers.  Sadly, we must resort to an arbitrary delay in the
+   * test code, and hope that after this delay the two threads are both blocked.
+   */
+  rc = usleep(THREAD_START_DELAY_MS * 1000);
+  ASSERT_EQ(rc, 0);
+
+  /*
+   * Releasing the write lock should unblock both the readers and they
+   * should then both be joinable.
+   */
+  rc = pthread_rwlock_unlock(&g_rwlock);
+
+  pthread_join(thread1, NULL);
+  pthread_join(thread2, NULL);
+}
+
+void test_reader_plus_writer(void) {
+  fprintf(stderr, "test_reader_plus_writer\n");
+  tell_thread_to_acquire_lock(READ_LOCK);
+
+  /*
+   * Now attempt to acquire the write lock on the main thread.
+   * This should fail.
+   */
+  int rc = pthread_rwlock_trywrlock(&g_rwlock);
+  ASSERT_EQ(rc, EBUSY);
+
+  tell_thread_to_release_lock();
+}
+
+void test_writer_plus_reader(void) {
+  fprintf(stderr, "test_writer_plus_reader\n");
+
+  /*
+   * First get the write lock.
+   */
+  int rc = pthread_rwlock_wrlock(&g_rwlock);
+  ASSERT_EQ(rc, 0);
+
+  /*
+   * Attempt to acquire read lock should now fail
+   */
+  rc = pthread_rwlock_tryrdlock(&g_rwlock);
+  ASSERT_EQ(rc, EBUSY);
+
+  rc = pthread_rwlock_unlock(&g_rwlock);
+  ASSERT_EQ(rc, 0);
+}
+
+void test_unlocked_with_zero_timestamp(void) {
+  fprintf(stderr, "test_unlocked_with_zero_timestamp\n");
+  int rc;
+  struct timespec abstime = { 0, 0 };
+  ASSERT_EQ(g_thread_has_lock, 0);
+  fprintf(stderr, "Trying to lock the unlocked rwlock with a valid "
+          "zero absolute timestamp. "
+          "Expected to succeed instantly since the lock is free.\n");
+  rc = pthread_rwlock_timedrdlock(&g_rwlock, &abstime);
+  ASSERT_EQ(rc, 0);
+  rc = pthread_rwlock_unlock(&g_rwlock);
+  ASSERT_EQ(rc, 0);
+}
+
+int main(int argc, char **argv) {
+  int rc;
+  fprintf(stderr, "Running...\n");
+
+  pthread_rwlockattr_t attrs;
+  rc = pthread_rwlockattr_init(&attrs);
+  ASSERT_EQ(rc, 0);
+  int shared = -1;
+  rc = pthread_rwlockattr_getpshared(&attrs, &shared);
+  ASSERT_EQ(rc, 0);
+  ASSERT_EQ(shared, PTHREAD_PROCESS_PRIVATE);
+  rc = pthread_rwlockattr_setpshared(&attrs, PTHREAD_PROCESS_SHARED);
+  ASSERT_EQ(rc, 0);
+  rc = pthread_rwlockattr_setpshared(&attrs, PTHREAD_PROCESS_PRIVATE);
+  ASSERT_EQ(rc, 0);
+  rc = pthread_rwlock_init(&g_rwlock, &attrs);
+  ASSERT_EQ(rc, 0);
+  rc = pthread_rwlockattr_destroy(&attrs);
+  ASSERT_EQ(rc, 0);
+
+  pthread_t thread;
+  rc = pthread_create(&thread, NULL, locking_thread, NULL);
+  ASSERT_EQ(rc, 0);
+  fprintf(stderr, "Thread started.\n");
+
+  test_unlocked_with_zero_timestamp();
+  test_multiple_readers();
+  test_multiple_writers();
+  test_reader_plus_writer();
+  test_writer_plus_reader();
+  test_reader_timedwait();
+  test_writer_timedwait();
+  test_recursive_reader();
+  test_multiple_reader_wakeup();
+
+  rc = pthread_rwlock_destroy(&g_rwlock);
+  ASSERT_EQ(rc, 0);
+  fprintf(stderr, "Done.\n");
+  return 0;
+}