memory/volatile/VolatileBufferAshmem.cpp

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #include "VolatileBuffer.h"
   6 #include "mozilla/Assertions.h"
   7 #include "mozilla/mozalloc.h"
   8
   9 #include <fcntl.h>
  10 #include <sys/mman.h>
  11 #include <sys/stat.h>
  12 #include <sys/types.h>
  13 #include <unistd.h>
  14
  15 #include "mozilla/Ashmem.h"
  16
  17 #ifdef MOZ_MEMORY
  18 extern "C" int posix_memalign(void** memptr, size_t alignment, size_t size);
  19 #endif
  20
  21 #define MIN_VOLATILE_ALLOC_SIZE 8192
  22
  23 namespace mozilla {
  24
  25 VolatileBuffer::VolatileBuffer()
  26     : mMutex("VolatileBuffer"),
  27       mBuf(nullptr),
  28       mSize(0),
  29       mLockCount(0),
  30       mFd(-1) {}
  31
  32 bool VolatileBuffer::Init(size_t aSize, size_t aAlignment) {
  33   MOZ_ASSERT(!mSize && !mBuf, "Init called twice");
  34   MOZ_ASSERT(!(aAlignment % sizeof(void*)),
  35              "Alignment must be multiple of pointer size");
  36
  37   mSize = aSize;
  38   if (aSize < MIN_VOLATILE_ALLOC_SIZE) {
  39     goto heap_alloc;
  40   }
  41
  42   mFd = mozilla::android::ashmem_create(nullptr, mSize);
  43   if (mFd < 0) {
  44     goto heap_alloc;
  45   }
  46
  47   mBuf = mmap(nullptr, mSize, PROT_READ | PROT_WRITE, MAP_SHARED, mFd, 0);
  48   if (mBuf != MAP_FAILED) {
  49     return true;
  50   }
  51
  52 heap_alloc:
  53   mBuf = nullptr;
  54   if (mFd >= 0) {
  55     close(mFd);
  56     mFd = -1;
  57   }
  58
  59 #ifdef MOZ_MEMORY
  60   posix_memalign(&mBuf, aAlignment, aSize);
  61 #else
  62   mBuf = memalign(aAlignment, aSize);
  63 #endif
  64   return !!mBuf;
  65 }
  66
  67 VolatileBuffer::~VolatileBuffer() {
  68   MOZ_ASSERT(mLockCount == 0, "Being destroyed with non-zero lock count?");
  69
  70   if (OnHeap()) {
  71     free(mBuf);
  72   } else {
  73     munmap(mBuf, mSize);
  74     close(mFd);
  75   }
  76 }
  77
  78 bool VolatileBuffer::Lock(void** aBuf) {
  79   MutexAutoLock lock(mMutex);
  80
  81   MOZ_ASSERT(mBuf, "Attempting to lock an uninitialized VolatileBuffer");
  82
  83   *aBuf = mBuf;
  84   if (++mLockCount > 1 || OnHeap()) {
  85     return true;
  86   }
  87
  88   // Zero offset and zero length means we want to pin/unpin the entire thing.
  89   struct ashmem_pin pin = {0, 0};
  90   return ioctl(mFd, ASHMEM_PIN, &pin) == ASHMEM_NOT_PURGED;
  91 }
  92
  93 void VolatileBuffer::Unlock() {
  94   MutexAutoLock lock(mMutex);
  95
  96   MOZ_ASSERT(mLockCount > 0, "VolatileBuffer unlocked too many times!");
  97   if (--mLockCount || OnHeap()) {
  98     return;
  99   }
 100
 101   struct ashmem_pin pin = {0, 0};
 102   ioctl(mFd, ASHMEM_UNPIN, &pin);
 103 }
 104
 105 bool VolatileBuffer::OnHeap() const { return mFd < 0; }
 106
 107 size_t VolatileBuffer::HeapSizeOfExcludingThis(
 108     MallocSizeOf aMallocSizeOf) const {
 109   return OnHeap() ? aMallocSizeOf(mBuf) : 0;
 110 }
 111
 112 size_t VolatileBuffer::NonHeapSizeOfExcludingThis() const {
 113   if (OnHeap()) {
 114     return 0;
 115   }
 116
 117   return (mSize + (PAGE_SIZE - 1)) & PAGE_MASK;
 118 }
 119
 120 }  // namespace mozilla