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.release()),
  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   // Shutdown() must have been called before.
  31   DCHECK(!loader_);
  32 }
  33
  34 void AsyncPolicyProvider::Init(SchemaRegistry* registry) {
  35   DCHECK(CalledOnValidThread());
  36   ConfigurationPolicyProvider::Init(registry);
  37
  38   if (!loader_)
  39     return;
  40
  41   AsyncPolicyLoader::UpdateCallback callback =
  42       base::Bind(&AsyncPolicyProvider::LoaderUpdateCallback,
  43                  base::MessageLoopProxy::current(),
  44                  weak_factory_.GetWeakPtr());
  45   bool post = loader_->task_runner()->PostTask(
  46       FROM_HERE,
  47       base::Bind(&AsyncPolicyLoader::Init,
  48                  base::Unretained(loader_),
  49                  callback));
  50   DCHECK(post) << "AsyncPolicyProvider::Init() called with threads not running";
  51 }
  52
  53 void AsyncPolicyProvider::Shutdown() {
  54   DCHECK(CalledOnValidThread());
  55   // Note on the lifetime of |loader_|:
  56   // The |loader_| lives on the background thread, and is deleted from here.
  57   // This means that posting tasks on the |loader_| to the background thread
  58   // from the AsyncPolicyProvider is always safe, since a potential DeleteSoon()
  59   // is only posted from here. The |loader_| posts back to the
  60   // AsyncPolicyProvider through the |update_callback_|, which has a WeakPtr to
  61   // |this|.
  62   if (!loader_->task_runner()->DeleteSoon(FROM_HERE, loader_)) {
  63     // The background thread doesn't exist; this only happens on unit tests.
  64     delete loader_;
  65   }
  66   loader_ = NULL;
  67   ConfigurationPolicyProvider::Shutdown();
  68 }
  69
  70 void AsyncPolicyProvider::RefreshPolicies() {
  71   DCHECK(CalledOnValidThread());
  72
  73   // Subtle: RefreshPolicies() has a contract that requires the next policy
  74   // update notification (triggered from UpdatePolicy()) to reflect any changes
  75   // made before this call. So if a caller has modified the policy settings and
  76   // invoked RefreshPolicies(), then by the next notification these policies
  77   // should already be provided.
  78   // However, it's also possible that an asynchronous Reload() is in progress
  79   // and just posted OnLoaderReloaded(). Therefore a task is posted to the
  80   // background thread before posting the next Reload, to prevent a potential
  81   // concurrent Reload() from triggering a notification too early. If another
  82   // refresh task has been posted, it is invalidated now.
  83   if (!loader_)
  84     return;
  85   refresh_callback_.Reset(
  86       base::Bind(&AsyncPolicyProvider::ReloadAfterRefreshSync,
  87                  weak_factory_.GetWeakPtr()));
  88   loader_->task_runner()->PostTaskAndReply(
  89       FROM_HERE,
  90       base::Bind(base::DoNothing),
  91       refresh_callback_.callback());
  92 }
  93
  94 void AsyncPolicyProvider::ReloadAfterRefreshSync() {
  95   DCHECK(CalledOnValidThread());
  96   // This task can only enter if it was posted from RefreshPolicies(), and it
  97   // hasn't been cancelled meanwhile by another call to RefreshPolicies().
  98   DCHECK(!refresh_callback_.IsCancelled());
  99   // There can't be another refresh callback pending now, since its creation
 100   // in RefreshPolicies() would have cancelled the current execution. So it's
 101   // safe to cancel the |refresh_callback_| now, so that OnLoaderReloaded()
 102   // sees that there is no refresh pending.
 103   refresh_callback_.Cancel();
 104
 105   if (!loader_)
 106     return;
 107
 108   loader_->task_runner()->PostTask(
 109       FROM_HERE,
 110       base::Bind(&AsyncPolicyLoader::RefreshPolicies,
 111                  base::Unretained(loader_),
 112                  schema_map()));
 113 }
 114
 115 void AsyncPolicyProvider::OnLoaderReloaded(scoped_ptr<PolicyBundle> bundle) {
 116   DCHECK(CalledOnValidThread());
 117   // Only propagate policy updates if there are no pending refreshes, and if
 118   // Shutdown() hasn't been called yet.
 119   if (refresh_callback_.IsCancelled() && loader_)
 120     UpdatePolicy(bundle.Pass());
 121 }
 122
 123 // static
 124 void AsyncPolicyProvider::LoaderUpdateCallback(
 125     scoped_refptr<base::MessageLoopProxy> loop,
 126     base::WeakPtr<AsyncPolicyProvider> weak_this,
 127     scoped_ptr<PolicyBundle> bundle) {
 128   loop->PostTask(FROM_HERE,
 129                  base::Bind(&AsyncPolicyProvider::OnLoaderReloaded,
 130                             weak_this,
 131                             base::Passed(&bundle)));
 132 }
 133
 134 }  // namespace policy