Get rid of recursive locks for job based recompilation

src/optimizing-compiler-thread.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/optimizing-compiler-thread.h"
 
 #include "src/v8.h"
 
 #include "src/base/atomicops.h"
 #include "src/full-codegen.h"
@@ skipping 24 matching lines @@
     }
   }
   delete info;
 }
 
 }  // namespace
 
 
 class OptimizingCompilerThread::CompileTask : public v8::Task {
  public:
-  explicit CompileTask(Isolate* isolate) : isolate_(isolate) {}
+  explicit CompileTask(Isolate* isolate) : isolate_(isolate) {
+    base::NoBarrier_AtomicIncrement(
+        &isolate_->optimizing_compiler_thread()->ref_count_, 1);
+  }
 
   virtual ~CompileTask() {}
 
  private:
   // v8::Task overrides.
   void Run() OVERRIDE {
     DisallowHeapAllocation no_allocation;
     DisallowHandleAllocation no_handles;
     DisallowHandleDereference no_deref;
 
     OptimizingCompilerThread* thread = isolate_->optimizing_compiler_thread();
+    StopFlag flag;
 
     {
       TimerEventScope<TimerEventRecompileConcurrent> timer(isolate_);
 
       if (thread->recompilation_delay_ != 0) {
         base::OS::Sleep(thread->recompilation_delay_);
       }
 
-      StopFlag flag;
       OptimizedCompileJob* job = thread->NextInput(&flag);
 
-      if (flag == CONTINUE) {
-        thread->CompileNext(job);
-      } else {
-        AllowHandleDereference allow_handle_dereference;
-        if (!job->info()->is_osr()) {
-          DisposeOptimizedCompileJob(job, true);
+      switch (flag) {
+        case CONTINUE:
+          thread->CompileNext(job);
+          break;
+
+        case STOP:
+        case FLUSH: {
+          AllowHandleDereference allow_handle_dereference;
+          if (!job->info()->is_osr()) {
+            DisposeOptimizedCompileJob(job, true);
+          }
+          break;
         }
       }
     }
+    if (flag == STOP) {
+      base::Release_Store(&thread->stop_thread_,
+                          static_cast<base::AtomicWord>(CONTINUE));
+      thread->stop_semaphore_.Signal();
+    }
 
-    bool signal = false;
-    {
-      base::LockGuard<base::RecursiveMutex> lock(&thread->task_count_mutex_);
-      if (--thread->task_count_ == 0) {
-        if (static_cast<StopFlag>(base::Acquire_Load(&thread->stop_thread_)) ==
-            FLUSH) {
-          base::Release_Store(&thread->stop_thread_,
-                              static_cast<base::AtomicWord>(CONTINUE));
-          signal = true;
-        }
-      }
+    if (base::NoBarrier_AtomicIncrement(&thread->ref_count_, -1) == 0) {
+      thread->stop_semaphore_.Signal();
     }
-    if (signal) thread->stop_semaphore_.Signal();
   }
 
   Isolate* isolate_;
 
   DISALLOW_COPY_AND_ASSIGN(CompileTask);
 };
 
 
 OptimizingCompilerThread::~OptimizingCompilerThread() {
+  if (base::NoBarrier_AtomicIncrement(&ref_count_, -1) > 0) {
+    stop_semaphore_.Wait();
+  }
   DCHECK_EQ(0, input_queue_length_);
   DeleteArray(input_queue_);
   if (FLAG_concurrent_osr) {
 #ifdef DEBUG
     for (int i = 0; i < osr_buffer_capacity_; i++) {
       CHECK_NULL(osr_buffer_[i]);
     }
 #endif
     DeleteArray(osr_buffer_);
   }
@@ skipping 65 matching lines @@
       UNREACHABLE();
       *flag = CONTINUE;
     }
     return NULL;
   }
   OptimizedCompileJob* job = input_queue_[InputQueueIndex(0)];
   DCHECK_NOT_NULL(job);
   input_queue_shift_ = InputQueueIndex(1);
   input_queue_length_--;
   if (flag) {
-    *flag = static_cast<StopFlag>(base::Acquire_Load(&stop_thread_));
+    switch (static_cast<StopFlag>(base::Acquire_Load(&stop_thread_))) {
+      case CONTINUE:
+        *flag = CONTINUE;
+        break;
+
+      case FLUSH:
+        if (input_queue_length_ == 0)
+          *flag = STOP;

[Yang, 2015/02/24 09:57:13]

I'd prefer having brackets around if-else blocks. But we could also use a
ternary operator.

+        else
+          *flag = FLUSH;
+        break;
+
+      case STOP:
+        UNREACHABLE();
+        *flag = CONTINUE;
+        break;
+    }
   }
   return job;
 }
 
 
 void OptimizingCompilerThread::CompileNext(OptimizedCompileJob* job) {
   DCHECK_NOT_NULL(job);
 
   // The function may have already been optimized by OSR.  Simply continue.
   OptimizedCompileJob::Status status = job->OptimizeGraph();
@@ skipping 44 matching lines @@
       osr_buffer_[i] = NULL;
     }
   }
 }
 
 
 void OptimizingCompilerThread::Flush() {
   DCHECK(!IsOptimizerThread());
   bool block = true;
   if (job_based_recompilation_) {
-    base::LockGuard<base::RecursiveMutex> lock(&task_count_mutex_);
-    block = task_count_ > 0 || blocked_jobs_ > 0;
-    if (block) {
-      base::Release_Store(&stop_thread_, static_cast<base::AtomicWord>(FLUSH));
+    if (FLAG_block_concurrent_recompilation) Unblock();
+    {
+      base::LockGuard<base::Mutex> lock(&input_queue_mutex_);
+      block = input_queue_length_ > 0;
+      if (block) {
+        base::Release_Store(&stop_thread_,
+                            static_cast<base::AtomicWord>(FLUSH));
+      }
     }
-    if (FLAG_block_concurrent_recompilation) Unblock();
   } else {
     base::Release_Store(&stop_thread_, static_cast<base::AtomicWord>(FLUSH));
     if (FLAG_block_concurrent_recompilation) Unblock();
   }
   if (!job_based_recompilation_) input_queue_semaphore_.Signal();
   if (block) stop_semaphore_.Wait();
   FlushOutputQueue(true);
   if (FLAG_concurrent_osr) FlushOsrBuffer(true);
   if (tracing_enabled_) {
     PrintF("  ** Flushed concurrent recompilation queues.\n");
   }
 }
 
 
 void OptimizingCompilerThread::Stop() {
   DCHECK(!IsOptimizerThread());
   bool block = true;
   if (job_based_recompilation_) {
-    base::LockGuard<base::RecursiveMutex> lock(&task_count_mutex_);
-    block = task_count_ > 0 || blocked_jobs_ > 0;
-    if (block) {
-      base::Release_Store(&stop_thread_, static_cast<base::AtomicWord>(FLUSH));
+    if (FLAG_block_concurrent_recompilation) Unblock();
+    {
+      base::LockGuard<base::Mutex> lock(&input_queue_mutex_);
+      block = input_queue_length_ > 0;
+      if (block) {
+        base::Release_Store(&stop_thread_,
+                            static_cast<base::AtomicWord>(FLUSH));
+      }
     }
-    if (FLAG_block_concurrent_recompilation) Unblock();
   } else {
     base::Release_Store(&stop_thread_, static_cast<base::AtomicWord>(STOP));
     if (FLAG_block_concurrent_recompilation) Unblock();
   }
   if (!job_based_recompilation_) input_queue_semaphore_.Signal();
   if (block) stop_semaphore_.Wait();
 
   if (recompilation_delay_ != 0) {
     // At this point the optimizing compiler thread's event loop has stopped.
     // There is no need for a mutex when reading input_queue_length_.
@@ skipping 75 matching lines @@
   } else {
     // Add job to the back of the input queue.
     base::LockGuard<base::Mutex> access_input_queue(&input_queue_mutex_);
     DCHECK_LT(input_queue_length_, input_queue_capacity_);
     input_queue_[InputQueueIndex(input_queue_length_)] = job;
     input_queue_length_++;
   }
   if (FLAG_block_concurrent_recompilation) {
     blocked_jobs_++;
   } else if (job_based_recompilation_) {
-    base::LockGuard<base::RecursiveMutex> lock(&task_count_mutex_);
-    ++task_count_;
     V8::GetCurrentPlatform()->CallOnBackgroundThread(
         new CompileTask(isolate_), v8::Platform::kShortRunningTask);
   } else {
     input_queue_semaphore_.Signal();
   }
 }
 
 
 void OptimizingCompilerThread::Unblock() {
   DCHECK(!IsOptimizerThread());
-  {
-    base::LockGuard<base::RecursiveMutex> lock(&task_count_mutex_);
-    task_count_ += blocked_jobs_;
-  }
   while (blocked_jobs_ > 0) {
     if (job_based_recompilation_) {
       V8::GetCurrentPlatform()->CallOnBackgroundThread(
           new CompileTask(isolate_), v8::Platform::kShortRunningTask);
     } else {
       input_queue_semaphore_.Signal();
     }
     blocked_jobs_--;
   }
 }
@@ skipping 76 matching lines @@
 
 
 bool OptimizingCompilerThread::IsOptimizerThread() {
   base::LockGuard<base::Mutex> lock_guard(&thread_id_mutex_);
   return ThreadId::Current().ToInteger() == thread_id_;
 }
 #endif
 
 
 } }  // namespace v8::internal