components/policy/core/common/async_policy_provider.cc

   1 // Copyright 2013 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 "components/policy/core/common/async_policy_provider.h"
   6
   7 #include "base/bind.h"
   8 #include "base/bind_helpers.h"
   9 #include "base/location.h"
  10 #include "base/message_loop/message_loop.h"
  11 #include "base/message_loop/message_loop_proxy.h"
  12 #include "base/sequenced_task_runner.h"
  13 #include "components/policy/core/common/async_policy_loader.h"
  14 #include "components/policy/core/common/policy_bundle.h"
  15 #include "components/policy/core/common/schema_registry.h"
  16
  17 namespace policy {
  18
  19 AsyncPolicyProvider::AsyncPolicyProvider(
  20     SchemaRegistry* registry,
  21     scoped_ptr<AsyncPolicyLoader> loader)
  22     : loader_(loader.Pass()),
  23       weak_factory_(this) {
  24   // Make an immediate synchronous load on startup.
  25   OnLoaderReloaded(loader_->InitialLoad(registry->schema_map()));
  26 }
  27
  28 AsyncPolicyProvider::~AsyncPolicyProvider() {
  29   DCHECK(CalledOnValidThread());
  30 }
  31
  32 void AsyncPolicyProvider::Init(SchemaRegistry* registry) {
  33   DCHECK(CalledOnValidThread());
  34   ConfigurationPolicyProvider::Init(registry);
  35
  36   if (!loader_)
  37     return;
  38
  39   AsyncPolicyLoader::UpdateCallback callback =
  40       base::Bind(&AsyncPolicyProvider::LoaderUpdateCallback,
  41                  base::MessageLoopProxy::current(),
  42                  weak_factory_.GetWeakPtr());
  43   bool post = loader_->task_runner()->PostTask(
  44       FROM_HERE,
  45       base::Bind(&AsyncPolicyLoader::Init,
  46                  base::Unretained(loader_.get()),
  47                  callback));
  48   DCHECK(post) << "AsyncPolicyProvider::Init() called with threads not running";
  49 }
  50
  51 void AsyncPolicyProvider::Shutdown() {
  52   DCHECK(CalledOnValidThread());
  53   // Note on the lifetime of |loader_|:
  54   // The |loader_| lives on the background thread, and is deleted from here.
  55   // This means that posting tasks on the |loader_| to the background thread
  56   // from the AsyncPolicyProvider is always safe, since a potential DeleteSoon()
  57   // is only posted from here. The |loader_| posts back to the
  58   // AsyncPolicyProvider through the |update_callback_|, which has a WeakPtr to
  59   // |this|.
  60   // If threads are spinning, delete the loader on the thread it lives on. If
  61   // there are no threads, kill it immediately.
  62   AsyncPolicyLoader* loader_to_delete = loader_.release();
  63   if (!loader_to_delete->task_runner()->DeleteSoon(FROM_HERE, loader_to_delete))
  64     delete loader_to_delete;
  65   ConfigurationPolicyProvider::Shutdown();
  66 }
  67
  68 void AsyncPolicyProvider::RefreshPolicies() {
  69   DCHECK(CalledOnValidThread());
  70
  71   // Subtle: RefreshPolicies() has a contract that requires the next policy
  72   // update notification (triggered from UpdatePolicy()) to reflect any changes
  73   // made before this call. So if a caller has modified the policy settings and
  74   // invoked RefreshPolicies(), then by the next notification these policies
  75   // should already be provided.
  76   // However, it's also possible that an asynchronous Reload() is in progress
  77   // and just posted OnLoaderReloaded(). Therefore a task is posted to the
  78   // background thread before posting the next Reload, to prevent a potential
  79   // concurrent Reload() from triggering a notification too early. If another
  80   // refresh task has been posted, it is invalidated now.
  81   if (!loader_)
  82     return;
  83   refresh_callback_.Reset(
  84       base::Bind(&AsyncPolicyProvider::ReloadAfterRefreshSync,
  85                  weak_factory_.GetWeakPtr()));
  86   loader_->task_runner()->PostTaskAndReply(
  87       FROM_HERE,
  88       base::Bind(base::DoNothing),
  89       refresh_callback_.callback());
  90 }
  91
  92 void AsyncPolicyProvider::ReloadAfterRefreshSync() {
  93   DCHECK(CalledOnValidThread());
  94   // This task can only enter if it was posted from RefreshPolicies(), and it
  95   // hasn't been cancelled meanwhile by another call to RefreshPolicies().
  96   DCHECK(!refresh_callback_.IsCancelled());
  97   // There can't be another refresh callback pending now, since its creation
  98   // in RefreshPolicies() would have cancelled the current execution. So it's
  99   // safe to cancel the |refresh_callback_| now, so that OnLoaderReloaded()
 100   // sees that there is no refresh pending.
 101   refresh_callback_.Cancel();
 102
 103   if (!loader_)
 104     return;
 105
 106   loader_->task_runner()->PostTask(
 107       FROM_HERE,
 108       base::Bind(&AsyncPolicyLoader::RefreshPolicies,
 109                  base::Unretained(loader_.get()),
 110                  schema_map()));
 111 }
 112
 113 void AsyncPolicyProvider::OnLoaderReloaded(scoped_ptr<PolicyBundle> bundle) {
 114   DCHECK(CalledOnValidThread());
 115   // Only propagate policy updates if there are no pending refreshes, and if
 116   // Shutdown() hasn't been called yet.
 117   if (refresh_callback_.IsCancelled() && loader_)
 118     UpdatePolicy(bundle.Pass());
 119 }
 120
 121 // static
 122 void AsyncPolicyProvider::LoaderUpdateCallback(
 123     scoped_refptr<base::MessageLoopProxy> loop,
 124     base::WeakPtr<AsyncPolicyProvider> weak_this,
 125     scoped_ptr<PolicyBundle> bundle) {
 126   loop->PostTask(FROM_HERE,
 127                  base::Bind(&AsyncPolicyProvider::OnLoaderReloaded,
 128                             weak_this,
 129                             base::Passed(&bundle)));
 130 }
 131
 132 }  // namespace policy