Hook up the SequencedWorkerPool to the browser thread.

[re-land of 116816 http://codereview.chromium.org/9065009]

This does some refactoring of the static data in the browser thread so we only have one global object instead of a bunch fo separate arrays.

It also hooks up the visited link master's I/O to use this new system as a proof of concept.
Review URL: https://chromiumcodereview.appspot.com/9124033

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@118236 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 80 insertions, 15 deletions

diff --git a/base/threading/sequenced_worker_pool.cc b/base/threading/sequenced_worker_pool.cc
index 05ccff1..6d47068 100644
--- a/base/threading/sequenced_worker_pool.cc
+++ b/base/threading/sequenced_worker_pool.cc
@@ -57,20 +57,33 @@ class SequencedWorkerPool::Inner
   Inner(size_t max_threads, const std::string& thread_name_prefix);
   virtual ~Inner();
 
-  // Backends for SequenceWorkerPool.
   SequenceToken GetSequenceToken();
+
   SequenceToken GetNamedSequenceToken(const std::string& name);
-  bool PostTask(int sequence_token_id,
+
+  // This function accepts a name and an ID. If the name is null, the
+  // token ID is used. This allows us to implement the optional name lookup
+  // from a single function without having to enter the lock a separate time.
+  bool PostTask(const std::string* optional_token_name,
+                int sequence_token_id,
                 SequencedWorkerPool::WorkerShutdown shutdown_behavior,
                 const tracked_objects::Location& from_here,
                 const base::Closure& task);
+
+  void Flush();
+
   void Shutdown();
+
   void SetTestingObserver(SequencedWorkerPool::TestingObserver* observer);
 
   // Runs the worker loop on the background thread.
   void ThreadLoop(Worker* this_worker);
 
  private:
+  // Called from within the lock, this converts the given token name into a
+  // token ID, creating a new one if necessary.
+  int LockedGetNamedTokenID(const std::string& name);
+
   // The calling code should clear the given delete_these_oustide_lock
   // vector the next time the lock is released. See the implementation for
   // a more detailed description.
@@ -235,18 +248,11 @@ SequencedWorkerPool::SequenceToken
 SequencedWorkerPool::Inner::GetNamedSequenceToken(
     const std::string& name) {
   base::AutoLock lock(lock_);
-  std::map<std::string, int>::const_iterator found =
-      named_sequence_tokens_.find(name);
-  if (found != named_sequence_tokens_.end())
-    return SequenceToken(found->second);  // Got an existing one.
-
-  // Create a new one for this name.
-  SequenceToken result = GetSequenceToken();
-  named_sequence_tokens_.insert(std::make_pair(name, result.id_));
-  return result;
+  return SequenceToken(LockedGetNamedTokenID(name));
 }
 
 bool SequencedWorkerPool::Inner::PostTask(
+    const std::string* optional_token_name,
     int sequence_token_id,
     SequencedWorkerPool::WorkerShutdown shutdown_behavior,
     const tracked_objects::Location& from_here,
@@ -263,6 +269,10 @@ bool SequencedWorkerPool::Inner::PostTask(
     if (terminating_)
       return false;
 
+    // Now that we have the lock, apply the named token rules.
+    if (optional_token_name)
+      sequenced.sequence_token_id = LockedGetNamedTokenID(*optional_token_name);
+
     pending_tasks_.push_back(sequenced);
     pending_task_count_++;
     if (shutdown_behavior == BLOCK_SHUTDOWN)
@@ -281,6 +291,15 @@ bool SequencedWorkerPool::Inner::PostTask(
   return true;
 }
 
+void SequencedWorkerPool::Inner::Flush() {
+  {
+    base::AutoLock lock(lock_);
+    while (pending_task_count_ > 0 || waiting_thread_count_ < threads_.size())
+      cond_var_.Wait();
+  }
+  cond_var_.Signal();
+}
+
 void SequencedWorkerPool::Inner::Shutdown() {
   if (shutdown_called_)
     return;
@@ -366,6 +385,8 @@ void SequencedWorkerPool::Inner::ThreadLoop(Worker* this_worker) {
         if (terminating_)
           break;
         waiting_thread_count_++;
+        cond_var_.Signal();  // For Flush() that may be waiting on the
+                             // waiting thread count to go up.
         cond_var_.Wait();
         waiting_thread_count_--;
       }
@@ -377,6 +398,22 @@ void SequencedWorkerPool::Inner::ThreadLoop(Worker* this_worker) {
   cond_var_.Signal();
 }
 
+int SequencedWorkerPool::Inner::LockedGetNamedTokenID(
+    const std::string& name) {
+  lock_.AssertAcquired();
+  DCHECK(!name.empty());
+
+  std::map<std::string, int>::const_iterator found =
+      named_sequence_tokens_.find(name);
+  if (found != named_sequence_tokens_.end())
+    return found->second;  // Got an existing one.
+
+  // Create a new one for this name.
+  SequenceToken result = GetSequenceToken();
+  named_sequence_tokens_.insert(std::make_pair(name, result.id_));
+  return result.id_;
+}
+
 bool SequencedWorkerPool::Inner::GetWork(
     SequencedTask* task,
     std::vector<base::Closure>* delete_these_outside_lock) {
@@ -593,33 +630,45 @@ SequencedWorkerPool::SequenceToken SequencedWorkerPool::GetNamedSequenceToken(
 bool SequencedWorkerPool::PostWorkerTask(
     const tracked_objects::Location& from_here,
     const base::Closure& task) {
-  return inner_->PostTask(0, BLOCK_SHUTDOWN, from_here, task);
+  return inner_->PostTask(NULL, 0, BLOCK_SHUTDOWN, from_here, task);
 }
 
 bool SequencedWorkerPool::PostWorkerTaskWithShutdownBehavior(
     const tracked_objects::Location& from_here,
     const base::Closure& task,
     WorkerShutdown shutdown_behavior) {
-  return inner_->PostTask(0, shutdown_behavior, from_here, task);
+  return inner_->PostTask(NULL, 0, shutdown_behavior, from_here, task);
 }
 
 bool SequencedWorkerPool::PostSequencedWorkerTask(
     SequenceToken sequence_token,
     const tracked_objects::Location& from_here,
     const base::Closure& task) {
-  return inner_->PostTask(sequence_token.id_, BLOCK_SHUTDOWN,
+  return inner_->PostTask(NULL, sequence_token.id_, BLOCK_SHUTDOWN,
                           from_here, task);
 }
 
+bool SequencedWorkerPool::PostNamedSequencedWorkerTask(
+    const std::string& token_name,
+    const tracked_objects::Location& from_here,
+    const base::Closure& task) {
+  DCHECK(!token_name.empty());
+  return inner_->PostTask(&token_name, 0, BLOCK_SHUTDOWN, from_here, task);
+}
+
 bool SequencedWorkerPool::PostSequencedWorkerTaskWithShutdownBehavior(
     SequenceToken sequence_token,
     const tracked_objects::Location& from_here,
     const base::Closure& task,
     WorkerShutdown shutdown_behavior) {
-  return inner_->PostTask(sequence_token.id_, shutdown_behavior,
+  return inner_->PostTask(NULL, sequence_token.id_, shutdown_behavior,
                           from_here, task);
 }
 
+void SequencedWorkerPool::FlushForTesting() {
+  inner_->Flush();
+}
+
 void SequencedWorkerPool::Shutdown() {
   inner_->Shutdown();
 }
diff --git a/base/threading/sequenced_worker_pool.h b/base/threading/sequenced_worker_pool.h
index c6e0560..f5770a7 100644
--- a/base/threading/sequenced_worker_pool.h
+++ b/base/threading/sequenced_worker_pool.h
@@ -172,6 +172,12 @@ class BASE_EXPORT SequencedWorkerPool {
                                const tracked_objects::Location& from_here,
                                const base::Closure& task);
 
+  // Like PostSequencedWorkerTask above, but allows you to specify a named
+  // token, which saves an extra call to GetNamedSequenceToken.
+  bool PostNamedSequencedWorkerTask(const std::string& token_name,
+                                    const tracked_objects::Location& from_here,
+                                    const base::Closure& task);
+
   // Same as PostSequencedWorkerTask but allows specification of the shutdown
   // behavior.
   bool PostSequencedWorkerTaskWithShutdownBehavior(
@@ -180,6 +186,16 @@ class BASE_EXPORT SequencedWorkerPool {
       const base::Closure& task,
       WorkerShutdown shutdown_behavior);
 
+  // Blocks until all pending tasks are complete. This should only be called in
+  // unit tests when you want to validate something that should have happened.
+  //
+  // Note that calling this will not prevent other threads from posting work to
+  // the queue while the calling thread is waiting on Flush(). In this case,
+  // Flush will return only when there's no more work in the queue. Normally,
+  // this doesn't come up sine in a test, all the work is being posted from
+  // the main thread.
+  void FlushForTesting();
+
   // Implements the worker pool shutdown. This should be called during app
   // shutdown, and will discard/join with appropriate tasks before returning.
   // After this call, subsequent calls to post tasks will fail.