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      1 /*
      2  * Copyright (C) 2016 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 #ifndef LIBMEMUNREACHABLE_SCOPED_DISABLE_MALLOC_H_
     18 #define LIBMEMUNREACHABLE_SCOPED_DISABLE_MALLOC_H_
     19 
     20 #include <memory>
     21 
     22 #include "android-base/macros.h"
     23 
     24 #include "bionic.h"
     25 #include "log.h"
     26 #include "ScopedAlarm.h"
     27 
     28 class DisableMallocGuard{
     29  public:
     30   DisableMallocGuard() : disabled_(false){}
     31   ~DisableMallocGuard() {
     32     Enable();
     33   }
     34 
     35   void Disable() {
     36     if (!disabled_) {
     37       malloc_disable();
     38       disabled_ = true;
     39     }
     40   }
     41 
     42   void Enable() {
     43     if (disabled_) {
     44       malloc_enable();
     45       disabled_ = false;
     46     }
     47   }
     48  private:
     49   DISALLOW_COPY_AND_ASSIGN(DisableMallocGuard);
     50   bool disabled_;
     51 };
     52 
     53 // Any calls to malloc or free from this thread will deadlock as long as this
     54 // object is in scope.  Calls to malloc from other threads may succeed (for
     55 // example if the allocation is satisfied out of the thread's tcache), or may
     56 // block until the object is destroyed.
     57 //
     58 // Don't call fork() while malloc is disabled, it needs the same locks held
     59 // here.
     60 class ScopedDisableMalloc {
     61  public:
     62   ScopedDisableMalloc() {
     63     disable_malloc_.Disable();
     64   }
     65 
     66   ~ScopedDisableMalloc() {
     67     disable_malloc_.Enable();
     68   }
     69 
     70  private:
     71   DISALLOW_COPY_AND_ASSIGN(ScopedDisableMalloc);
     72   DisableMallocGuard disable_malloc_;
     73 };
     74 
     75 class ScopedDisableMallocTimeout {
     76  public:
     77   ScopedDisableMallocTimeout(std::chrono::milliseconds timeout = std::chrono::milliseconds(2000)) :
     78     timeout_(timeout), timed_out_(false), disable_malloc_() {
     79     Disable();
     80   }
     81 
     82   ~ScopedDisableMallocTimeout() {
     83     Enable();
     84   }
     85 
     86   bool timed_out() {
     87     return timed_out_;
     88   }
     89 
     90   void Enable() {
     91     disable_malloc_.Enable();
     92     alarm_ = nullptr;
     93   }
     94 
     95   void Disable() {
     96     // set up the alarm before disabling malloc so unique_ptr can be used
     97     alarm_ = std::make_unique<ScopedAlarm>(timeout_, [&]() {
     98       disable_malloc_.Enable();
     99       timed_out_ = true;
    100     });
    101 
    102     disable_malloc_.Disable();
    103   }
    104 
    105  private:
    106   DISALLOW_COPY_AND_ASSIGN(ScopedDisableMallocTimeout);
    107   std::chrono::milliseconds timeout_;
    108   bool timed_out_;
    109   std::unique_ptr<ScopedAlarm> alarm_;
    110   DisableMallocGuard disable_malloc_;
    111 };
    112 
    113 #endif // LIBMEMUNREACHABLE_SCOPED_DISABLE_MALLOC_H_
    114