net/dns/serial_worker.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "net/dns/serial_worker.h"
   6
   7 #include "base/bind.h"
   8 #include "base/location.h"
   9 #include "base/message_loop/message_loop_proxy.h"
  10 #include "base/threading/worker_pool.h"
  11
  12 namespace net {
  13
  14 SerialWorker::SerialWorker()
  15   : message_loop_(base::MessageLoopProxy::current()),
  16     state_(IDLE) {}
  17
  18 SerialWorker::~SerialWorker() {}
  19
  20 void SerialWorker::WorkNow() {
  21   DCHECK(message_loop_->BelongsToCurrentThread());
  22   switch (state_) {
  23     case IDLE:
  24       if (!base::WorkerPool::PostTask(FROM_HERE, base::Bind(
  25           &SerialWorker::DoWorkJob, this), false)) {
  26 #if defined(OS_POSIX)
  27         // See worker_pool_posix.cc.
  28         NOTREACHED() << "WorkerPool::PostTask is not expected to fail on posix";
  29 #else
  30         LOG(WARNING) << "Failed to WorkerPool::PostTask, will retry later";
  31         const int kWorkerPoolRetryDelayMs = 100;
  32         message_loop_->PostDelayedTask(
  33             FROM_HERE,
  34             base::Bind(&SerialWorker::RetryWork, this),
  35             base::TimeDelta::FromMilliseconds(kWorkerPoolRetryDelayMs));
  36         state_ = WAITING;
  37         return;
  38 #endif
  39       }
  40       state_ = WORKING;
  41       return;
  42     case WORKING:
  43       // Remember to re-read after |DoRead| finishes.
  44       state_ = PENDING;
  45       return;
  46     case CANCELLED:
  47     case PENDING:
  48     case WAITING:
  49       return;
  50     default:
  51       NOTREACHED() << "Unexpected state " << state_;
  52   }
  53 }
  54
  55 void SerialWorker::Cancel() {
  56   DCHECK(message_loop_->BelongsToCurrentThread());
  57   state_ = CANCELLED;
  58 }
  59
  60 void SerialWorker::DoWorkJob() {
  61   this->DoWork();
  62   // If this fails, the loop is gone, so there is no point retrying.
  63   message_loop_->PostTask(FROM_HERE, base::Bind(
  64       &SerialWorker::OnWorkJobFinished, this));
  65 }
  66
  67 void SerialWorker::OnWorkJobFinished() {
  68   DCHECK(message_loop_->BelongsToCurrentThread());
  69   switch (state_) {
  70     case CANCELLED:
  71       return;
  72     case WORKING:
  73       state_ = IDLE;
  74       this->OnWorkFinished();
  75       return;
  76     case PENDING:
  77       state_ = IDLE;
  78       WorkNow();
  79       return;
  80     default:
  81       NOTREACHED() << "Unexpected state " << state_;
  82   }
  83 }
  84
  85 void SerialWorker::RetryWork() {
  86   DCHECK(message_loop_->BelongsToCurrentThread());
  87   switch (state_) {
  88     case CANCELLED:
  89       return;
  90     case WAITING:
  91       state_ = IDLE;
  92       WorkNow();
  93       return;
  94     default:
  95       NOTREACHED() << "Unexpected state " << state_;
  96   }
  97 }
  98
  99 }  // namespace net
 100