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      1 /*
      2  * Copyright (C) 2014 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #include "task_processor.h"
     18 
     19 #include "base/time_utils.h"
     20 #include "scoped_thread_state_change.h"
     21 
     22 namespace art {
     23 namespace gc {
     24 
     25 TaskProcessor::TaskProcessor()
     26     : lock_(new Mutex("Task processor lock", kReferenceProcessorLock)), is_running_(false),
     27       running_thread_(nullptr) {
     28   // Piggyback off the reference processor lock level.
     29   cond_.reset(new ConditionVariable("Task processor condition", *lock_));
     30 }
     31 
     32 TaskProcessor::~TaskProcessor() {
     33   delete lock_;
     34 }
     35 
     36 void TaskProcessor::AddTask(Thread* self, HeapTask* task) {
     37   ScopedThreadStateChange tsc(self, kBlocked);
     38   MutexLock mu(self, *lock_);
     39   tasks_.insert(task);
     40   cond_->Signal(self);
     41 }
     42 
     43 HeapTask* TaskProcessor::GetTask(Thread* self) {
     44   ScopedThreadStateChange tsc(self, kBlocked);
     45   MutexLock mu(self, *lock_);
     46   while (true) {
     47     if (tasks_.empty()) {
     48       if (!is_running_) {
     49         return nullptr;
     50       }
     51       cond_->Wait(self);  // Empty queue, wait until we are signalled.
     52     } else {
     53       // Non empty queue, look at the top element and see if we are ready to run it.
     54       const uint64_t current_time = NanoTime();
     55       HeapTask* task = *tasks_.begin();
     56       // If we are shutting down, return the task right away without waiting. Otherwise return the
     57       // task if it is late enough.
     58       uint64_t target_time = task->GetTargetRunTime();
     59       if (!is_running_ || target_time <= current_time) {
     60         tasks_.erase(tasks_.begin());
     61         return task;
     62       }
     63       DCHECK_GT(target_time, current_time);
     64       // Wait untl we hit the target run time.
     65       const uint64_t delta_time = target_time - current_time;
     66       const uint64_t ms_delta = NsToMs(delta_time);
     67       const uint64_t ns_delta = delta_time - MsToNs(ms_delta);
     68       cond_->TimedWait(self, static_cast<int64_t>(ms_delta), static_cast<int32_t>(ns_delta));
     69     }
     70   }
     71   UNREACHABLE();
     72 }
     73 
     74 void TaskProcessor::UpdateTargetRunTime(Thread* self, HeapTask* task, uint64_t new_target_time) {
     75   MutexLock mu(self, *lock_);
     76   // Find the task.
     77   auto range = tasks_.equal_range(task);
     78   for (auto it = range.first; it != range.second; ++it) {
     79     if (*it == task) {
     80       // Check if the target time was updated, if so re-insert then wait.
     81       if (new_target_time != task->GetTargetRunTime()) {
     82         tasks_.erase(it);
     83         task->SetTargetRunTime(new_target_time);
     84         tasks_.insert(task);
     85         // If we became the first task then we may need to signal since we changed the task that we
     86         // are sleeping on.
     87         if (*tasks_.begin() == task) {
     88           cond_->Signal(self);
     89         }
     90         return;
     91       }
     92     }
     93   }
     94 }
     95 
     96 bool TaskProcessor::IsRunning() const {
     97   MutexLock mu(Thread::Current(), *lock_);
     98   return is_running_;
     99 }
    100 
    101 Thread* TaskProcessor::GetRunningThread() const {
    102   MutexLock mu(Thread::Current(), *lock_);
    103   return running_thread_;
    104 }
    105 
    106 void TaskProcessor::Stop(Thread* self) {
    107   MutexLock mu(self, *lock_);
    108   is_running_ = false;
    109   running_thread_ = nullptr;
    110   cond_->Broadcast(self);
    111 }
    112 
    113 void TaskProcessor::Start(Thread* self) {
    114   MutexLock mu(self, *lock_);
    115   is_running_ = true;
    116   running_thread_ = self;
    117 }
    118 
    119 void TaskProcessor::RunAllTasks(Thread* self) {
    120   while (true) {
    121     // Wait and get a task, may be interrupted.
    122     HeapTask* task = GetTask(self);
    123     if (task != nullptr) {
    124       task->Run(self);
    125       task->Finalize();
    126     } else if (!IsRunning()) {
    127       break;
    128     }
    129   }
    130 }
    131 
    132 }  // namespace gc
    133 }  // namespace art
    134