pagespeed/system/apr_thread_compatible_pool.cc

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */


#include "pagespeed/system/apr_thread_compatible_pool.h"

#include <cstddef>

#include "apr_pools.h"
#include "apr_thread_mutex.h"

#include "base/logging.h"
#include "pagespeed/kernel/base/stack_buffer.h"

namespace net_instaweb {

apr_pool_t* AprCreateThreadCompatiblePool(apr_pool_t* parent_pool) {
  // Creates a pool that can be used in any thread, even when run in
  // Apache prefork.
  //
  // 1) Concurrent allocations from the same pools are not (thread)safe.
  // 2) Concurrent allocations from different pools using the same allocator
  //    are not safe unless the allocator has a mutex set.
  // 3) prefork's pchild pool (which is our ancestor) has an allocator without
  //    a mutex set.
  //
  // Note: the above is all about the release version of the pool code, the
  // checking one has some additional locking!
  apr_pool_t* pool = NULL;
  apr_allocator_t* allocator = NULL;
  CHECK(apr_allocator_create(&allocator) == APR_SUCCESS);
  apr_status_t status =
      apr_pool_create_ex(&pool, parent_pool, NULL /*abortfn*/, allocator);
  if ((status != APR_SUCCESS) || (pool == NULL)) {
    char buf[kStackBufferSize];
    apr_strerror(status, buf, sizeof(buf));
    CHECK_EQ(APR_SUCCESS, status) << "apr_pool_create_ex failed: " << buf;
    CHECK(pool != NULL) << "apr_pool_create_ex failed: " << buf;
  }
  apr_allocator_owner_set(allocator, pool);
  apr_thread_mutex_t* mutex;
  CHECK(apr_thread_mutex_create(&mutex, APR_THREAD_MUTEX_DEFAULT, pool) ==
        APR_SUCCESS);
  apr_allocator_mutex_set(allocator, mutex);
  return pool;
}

}  // namespace net_instaweb