initial code repo

[stor4nfv.git] / src / ceph / src / test / system / cross_process_sem.cc

diff --git a/src/ceph/src/test/system/cross_process_sem.cc b/src/ceph/src/test/system/cross_process_sem.cc
new file mode 100644 (file)
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+++ b/src/ceph/src/test/system/cross_process_sem.cc
@@ -0,0 +1,107 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+/*
+* Ceph - scalable distributed file system
+*
+* Copyright (C) 2011 New Dream Network
+*
+* This is free software; you can redistribute it and/or
+* modify it under the terms of the GNU Lesser General Public
+* License version 2.1, as published by the Free Software
+* Foundation.  See file COPYING.
+*
+*/
+
+#include "cross_process_sem.h"
+
+#include <errno.h>
+#include <semaphore.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+
+/* We put our cross-process semaphore into a page of memory mapped with mmap. */
+struct cross_process_sem_data_t
+{
+  sem_t sem;
+};
+
+/* A factory function is a good choice here because we want to be able to
+ * return an error code. It does force heap allocation, but that is the
+ * easiest way to use synchronization primitives anyway. Most programmers don't
+ * care about destroying semaphores before the process finishes. It's pretty
+ * difficult to get it right and there is usually no benefit.
+ */
+int CrossProcessSem::
+create(int initial_val, CrossProcessSem** res)
+{
+  struct cross_process_sem_data_t *data = static_cast < cross_process_sem_data_t*> (
+    mmap(NULL, sizeof(struct cross_process_sem_data_t),
+       PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, -1, 0));
+  if (data == MAP_FAILED) {
+    int err = errno;
+    return err;
+  }
+  int ret = sem_init(&data->sem, 1, initial_val);
+  if (ret) {
+    return ret;
+  }
+  *res = new CrossProcessSem(data);
+  return 0;
+}
+
+CrossProcessSem::
+~CrossProcessSem()
+{
+  munmap(m_data, sizeof(struct cross_process_sem_data_t));
+  m_data = NULL;
+}
+
+void CrossProcessSem::
+wait()
+{
+  while(true) {
+    int ret = sem_wait(&m_data->sem);
+    if (ret == 0)
+      return;
+    int err = errno;
+    if (err == -EINTR)
+      continue;
+    abort();
+  }
+}
+
+void CrossProcessSem::
+post()
+{
+  int ret = sem_post(&m_data->sem);
+  if (ret == -1) {
+    abort();
+  }
+}
+
+int CrossProcessSem::
+reinit(int dval)
+{
+  if (dval < 0)
+    return -EINVAL;
+  int cval;
+  if (sem_getvalue(&m_data->sem, &cval) == -1)
+    return errno;
+  if (cval < dval) {
+    int diff = dval - cval;
+    for (int i = 0; i < diff; ++i)
+      sem_post(&m_data->sem);
+  }
+  else {
+    int diff = cval - dval;
+    for (int i = 0; i < diff; ++i)
+      sem_wait(&m_data->sem);
+  }
+  return 0;
+}
+
+CrossProcessSem::
+CrossProcessSem(struct cross_process_sem_data_t *data)
+  : m_data(data)
+{
+}