Pass StatsTable shared memory via global descriptors on Posix rather than using named shared memory.

base/metrics/stats_table.cc

 // Copyright (c) 2011 The Chromium 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 "base/metrics/stats_table.h"
 
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/shared_memory.h"
 #include "base/process/process_handle.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/platform_thread.h"
 #include "base/threading/thread_local_storage.h"
 
 #if defined(OS_POSIX)
+#include "base/posix/global_descriptors.h"
 #include "errno.h"
+#include "ipc/ipc_descriptors.h"
 #endif
 
 namespace base {
 
 // The StatsTable uses a shared memory segment that is laid out as follows
 //
 // +-------------------------------------------+
 // | Version | Size | MaxCounters | MaxThreads |
 // +-------------------------------------------+
 // | Thread names table                        |
@@ skipping 52 matching lines @@
 inline int AlignOffset(int offset) {
   return (sizeof(int) - (offset % sizeof(int))) % sizeof(int);
 }
 
 inline int AlignedSize(int size) {
   return size + AlignOffset(size);
 }
 
 }  // namespace
 
-// The StatsTable::Private maintains convenience pointers into the
+// The StatsTable::Internal maintains convenience pointers into the
 // shared memory segment.  Use this class to keep the data structure
 // clean and accessible.
-class StatsTable::Private {
+class StatsTable::Internal {
  public:
   // Various header information contained in the memory mapped segment.
   struct TableHeader {
     int version;
     int size;
     int max_counters;
     int max_threads;
   };
 
-  // Construct a new Private based on expected size parameters, or
+  // Construct a new Internal based on expected size parameters, or
   // return NULL on failure.
-  static Private* New(const std::string& name, int size,
-                                int max_threads, int max_counters);
+  static Internal* New(const std::string& name,
+                       int size,
+                       int max_threads,
+                       int max_counters);
 
-  SharedMemory* shared_memory() { return &shared_memory_; }
+  SharedMemory* shared_memory() { return shared_memory_.get(); }
 
   // Accessors for our header pointers
   TableHeader* table_header() const { return table_header_; }
   int version() const { return table_header_->version; }
   int size() const { return table_header_->size; }
   int max_counters() const { return table_header_->max_counters; }
   int max_threads() const { return table_header_->max_threads; }
 
   // Accessors for our tables
   char* thread_name(int slot_id) const {
     return &thread_names_table_[
       (slot_id-1) * (StatsTable::kMaxThreadNameLength)];
   }
   PlatformThreadId* thread_tid(int slot_id) const {
     return &(thread_tid_table_[slot_id-1]);
   }
   int* thread_pid(int slot_id) const {
     return &(thread_pid_table_[slot_id-1]);
   }
   char* counter_name(int counter_id) const {
     return &counter_names_table_[
       (counter_id-1) * (StatsTable::kMaxCounterNameLength)];
   }
   int* row(int counter_id) const {
     return &data_table_[(counter_id-1) * max_threads()];
   }
 
  private:
   // Constructor is private because you should use New() instead.
-  Private()
-      : table_header_(NULL),
+  explicit Internal(SharedMemory* shared_memory)
+      : shared_memory_(shared_memory),
+        table_header_(NULL),
         thread_names_table_(NULL),
         thread_tid_table_(NULL),
         thread_pid_table_(NULL),
         counter_names_table_(NULL),
         data_table_(NULL) {
   }
 
+  // Create or open the SharedMemory used by the stats table.
+  static SharedMemory* CreateSharedMemory(int size);
+
   // Initializes the table on first access.  Sets header values
   // appropriately and zeroes all counters.
   void InitializeTable(void* memory, int size, int max_counters,
                        int max_threads);
 
   // Initializes our in-memory pointers into a pre-created StatsTable.
   void ComputeMappedPointers(void* memory);
 
-  SharedMemory shared_memory_;
+  scoped_ptr<SharedMemory> shared_memory_;
   TableHeader* table_header_;
   char* thread_names_table_;
   PlatformThreadId* thread_tid_table_;
   int* thread_pid_table_;
   char* counter_names_table_;
   int* data_table_;
+
+  DISALLOW_COPY_AND_ASSIGN(Internal);
 };
 
 // static
-StatsTable::Private* StatsTable::Private::New(const std::string& name,
-                                              int size,
-                                              int max_threads,
-                                              int max_counters) {
-  scoped_ptr<Private> priv(new Private());
-  if (!priv->shared_memory_.CreateNamed(name, true, size))
+StatsTable::Internal* StatsTable::Internal::New(const std::string& name,
+                                                int size,
+                                                int max_threads,
+                                                int max_counters) {
+  scoped_ptr<SharedMemory> shared_memory(CreateSharedMemory(size));
+  if (!shared_memory.get())
     return NULL;
-  if (!priv->shared_memory_.Map(size))
+  if (!shared_memory->Map(size))
     return NULL;
-  void* memory = priv->shared_memory_.memory();
+  void* memory = shared_memory->memory();
 
+  scoped_ptr<Internal> internal(new Internal(shared_memory.release()));
   TableHeader* header = static_cast<TableHeader*>(memory);
 
   // If the version does not match, then assume the table needs
   // to be initialized.
   if (header->version != kTableVersion)
-    priv->InitializeTable(memory, size, max_counters, max_threads);
+    internal->InitializeTable(memory, size, max_counters, max_threads);
 
   // We have a valid table, so compute our pointers.
-  priv->ComputeMappedPointers(memory);
+  internal->ComputeMappedPointers(memory);
 
-  return priv.release();
+  return internal.release();
 }
 
-void StatsTable::Private::InitializeTable(void* memory, int size,
+// static
+SharedMemory* StatsTable::Internal::CreateSharedMemory(int size) {
+#if defined(OS_POSIX)
+  GlobalDescriptors* global_descriptors = GlobalDescriptors::GetInstance();
+  if (global_descriptors->MaybeGet(kStatsTableSharedMemFd) != -1) {
+    // Open the shared memory file descriptor passed by the browser process.
+    FileDescriptor file_descriptor(
+        global_descriptors->Get(kStatsTableSharedMemFd), false);
+    return new SharedMemory(file_descriptor, false);
+  }
+  // Otherwise we need to create it.
+  scoped_ptr<SharedMemory> shared_memory(new SharedMemory());
+  if (!shared_memory->CreateAnonymous(size))
+    return NULL;
+  return shared_memory.release();
+#elif defined(OS_WIN)
+  scoped_ptr<SharedMemory> shared_memory(new SharedMemory());
+  if (!shared_memory.CreateNamed(name, true, size))
+    return NULL;
+  return shared_memory.release();
+#endif
+}
+
+void StatsTable::Internal::InitializeTable(void* memory, int size,
                                           int max_counters,
                                           int max_threads) {
   // Zero everything.
   memset(memory, 0, size);
 
   // Initialize the header.
   TableHeader* header = static_cast<TableHeader*>(memory);
   header->version = kTableVersion;
   header->size = size;
   header->max_counters = max_counters;
   header->max_threads = max_threads;
 }
 
-void StatsTable::Private::ComputeMappedPointers(void* memory) {
+void StatsTable::Internal::ComputeMappedPointers(void* memory) {
   char* data = static_cast<char*>(memory);
   int offset = 0;
 
   table_header_ = reinterpret_cast<TableHeader*>(data);
   offset += sizeof(*table_header_);
   offset += AlignOffset(offset);
 
   // Verify we're looking at a valid StatsTable.
   DCHECK_EQ(table_header_->version, kTableVersion);
 
@@ skipping 30 matching lines @@
 struct StatsTable::TLSData {
   StatsTable* table;
   int slot;
 };
 
 // We keep a singleton table which can be easily accessed.
 StatsTable* global_table = NULL;
 
 StatsTable::StatsTable(const std::string& name, int max_threads,
                        int max_counters)
-    : impl_(NULL),
+    : internal_(NULL),
       tls_index_(SlotReturnFunction) {
   int table_size =
-    AlignedSize(sizeof(Private::TableHeader)) +
+    AlignedSize(sizeof(Internal::TableHeader)) +
     AlignedSize((max_counters * sizeof(char) * kMaxCounterNameLength)) +
     AlignedSize((max_threads * sizeof(char) * kMaxThreadNameLength)) +
     AlignedSize(max_threads * sizeof(int)) +
     AlignedSize(max_threads * sizeof(int)) +
     AlignedSize((sizeof(int) * (max_counters * max_threads)));
 
-  impl_ = Private::New(name, table_size, max_threads, max_counters);
+  internal_ = Internal::New(name, table_size, max_threads, max_counters);
 
-  if (!impl_)
+  if (!internal_)
     DPLOG(ERROR) << "StatsTable did not initialize";
 }
 
 StatsTable::~StatsTable() {
   // Before we tear down our copy of the table, be sure to
   // unregister our thread.
   UnregisterThread();
 
   // Return ThreadLocalStorage.  At this point, if any registered threads
   // still exist, they cannot Unregister.
   tls_index_.Free();
 
   // Cleanup our shared memory.
-  delete impl_;
+  delete internal_;
 
   // If we are the global table, unregister ourselves.
   if (global_table == this)
     global_table = NULL;
 }
 
 StatsTable* StatsTable::current() {
   return global_table;
 }
 
 void StatsTable::set_current(StatsTable* value) {
   global_table = value;
 }
 
 int StatsTable::GetSlot() const {
   TLSData* data = GetTLSData();
   if (!data)
     return 0;
   return data->slot;
 }
 
 int StatsTable::RegisterThread(const std::string& name) {
   int slot = 0;
-  if (!impl_)
+  if (!internal_)
     return 0;
 
   // Registering a thread requires that we lock the shared memory
   // so that two threads don't grab the same slot.  Fortunately,
   // thread creation shouldn't happen in inner loops.
   {
-    SharedMemoryAutoLock lock(impl_->shared_memory());
+    SharedMemoryAutoLock lock(internal_->shared_memory());
     slot = FindEmptyThread();
     if (!slot) {
       return 0;
     }
 
     // We have space, so consume a column in the table.
     std::string thread_name = name;
     if (name.empty())
       thread_name = kUnknownName;
-    strlcpy(impl_->thread_name(slot), thread_name.c_str(),
+    strlcpy(internal_->thread_name(slot), thread_name.c_str(),
             kMaxThreadNameLength);
-    *(impl_->thread_tid(slot)) = PlatformThread::CurrentId();
-    *(impl_->thread_pid(slot)) = GetCurrentProcId();
+    *(internal_->thread_tid(slot)) = PlatformThread::CurrentId();
+    *(internal_->thread_pid(slot)) = GetCurrentProcId();
   }
 
   // Set our thread local storage.
   TLSData* data = new TLSData;
   data->table = this;
   data->slot = slot;
   tls_index_.Set(data);
   return slot;
 }
 
 int StatsTable::CountThreadsRegistered() const {
-  if (!impl_)
+  if (!internal_)
     return 0;
 
   // Loop through the shared memory and count the threads that are active.
   // We intentionally do not lock the table during the operation.
   int count = 0;
-  for (int index = 1; index <= impl_->max_threads(); index++) {
-    char* name = impl_->thread_name(index);
+  for (int index = 1; index <= internal_->max_threads(); index++) {
+    char* name = internal_->thread_name(index);
     if (*name != '\0')
       count++;
   }
   return count;
 }
 
 int StatsTable::FindCounter(const std::string& name) {
   // Note: the API returns counters numbered from 1..N, although
   // internally, the array is 0..N-1.  This is so that we can return
   // zero as "not found".
-  if (!impl_)
+  if (!internal_)
     return 0;
 
   // Create a scope for our auto-lock.
   {
     AutoLock scoped_lock(counters_lock_);
 
     // Attempt to find the counter.
     CountersMap::const_iterator iter;
     iter = counters_.find(name);
     if (iter != counters_.end())
       return iter->second;
   }
 
   // Counter does not exist, so add it.
   return AddCounter(name);
 }
 
 int* StatsTable::GetLocation(int counter_id, int slot_id) const {
-  if (!impl_)
+  if (!internal_)
     return NULL;
-  if (slot_id > impl_->max_threads())
+  if (slot_id > internal_->max_threads())
     return NULL;
 
-  int* row = impl_->row(counter_id);
+  int* row = internal_->row(counter_id);
   return &(row[slot_id-1]);
 }
 
 const char* StatsTable::GetRowName(int index) const {
-  if (!impl_)
+  if (!internal_)
     return NULL;
 
-  return impl_->counter_name(index);
+  return internal_->counter_name(index);
 }
 
 int StatsTable::GetRowValue(int index) const {
   return GetRowValue(index, 0);
 }
 
 int StatsTable::GetRowValue(int index, int pid) const {
-  if (!impl_)
+  if (!internal_)
     return 0;
 
   int rv = 0;
-  int* row = impl_->row(index);
-  for (int slot_id = 0; slot_id < impl_->max_threads(); slot_id++) {
-    if (pid == 0 || *impl_->thread_pid(slot_id) == pid)
+  int* row = internal_->row(index);
+  for (int slot_id = 0; slot_id < internal_->max_threads(); slot_id++) {
+    if (pid == 0 || *internal_->thread_pid(slot_id) == pid)
       rv += row[slot_id];
   }
   return rv;
 }
 
 int StatsTable::GetCounterValue(const std::string& name) {
   return GetCounterValue(name, 0);
 }
 
 int StatsTable::GetCounterValue(const std::string& name, int pid) {
-  if (!impl_)
+  if (!internal_)
     return 0;
 
   int row = FindCounter(name);
   if (!row)
     return 0;
   return GetRowValue(row, pid);
 }
 
 int StatsTable::GetMaxCounters() const {
-  if (!impl_)
+  if (!internal_)
     return 0;
-  return impl_->max_counters();
+  return internal_->max_counters();
 }
 
 int StatsTable::GetMaxThreads() const {
-  if (!impl_)
+  if (!internal_)
     return 0;
-  return impl_->max_threads();
+  return internal_->max_threads();
 }
 
 int* StatsTable::FindLocation(const char* name) {
   // Get the static StatsTable
   StatsTable *table = StatsTable::current();
   if (!table)
     return NULL;
 
   // Get the slot for this thread.  Try to register
   // it if none exists.
   int slot = table->GetSlot();
   if (!slot && !(slot = table->RegisterThread(std::string())))
     return NULL;
 
   // Find the counter id for the counter.
   std::string str_name(name);
   int counter = table->FindCounter(str_name);
 
   // Now we can find the location in the table.
   return table->GetLocation(counter, slot);
 }
 
 void StatsTable::UnregisterThread() {
   UnregisterThread(GetTLSData());
 }
 
 void StatsTable::UnregisterThread(TLSData* data) {
   if (!data)
     return;
-  DCHECK(impl_);
+  DCHECK(internal_);
 
   // Mark the slot free by zeroing out the thread name.
-  char* name = impl_->thread_name(data->slot);
+  char* name = internal_->thread_name(data->slot);
   *name = '\0';
 
   // Remove the calling thread's TLS so that it cannot use the slot.
   tls_index_.Set(NULL);
   delete data;
 }
 
 void StatsTable::SlotReturnFunction(void* data) {
   // This is called by the TLS destructor, which on some platforms has
   // already cleared the TLS info, so use the tls_data argument
   // rather than trying to fetch it ourselves.
   TLSData* tls_data = static_cast<TLSData*>(data);
   if (tls_data) {
     DCHECK(tls_data->table);
     tls_data->table->UnregisterThread(tls_data);
   }
 }
 
 int StatsTable::FindEmptyThread() const {
   // Note: the API returns slots numbered from 1..N, although
   // internally, the array is 0..N-1.  This is so that we can return
   // zero as "not found".
   //
   // The reason for doing this is because the thread 'slot' is stored
   // in TLS, which is always initialized to zero, not -1.  If 0 were
   // returned as a valid slot number, it would be confused with the
   // uninitialized state.
-  if (!impl_)
+  if (!internal_)
     return 0;
 
   int index = 1;
-  for (; index <= impl_->max_threads(); index++) {
-    char* name = impl_->thread_name(index);
+  for (; index <= internal_->max_threads(); index++) {
+    char* name = internal_->thread_name(index);
     if (!*name)
       break;
   }
-  if (index > impl_->max_threads())
+  if (index > internal_->max_threads())
     return 0;  // The table is full.
   return index;
 }
 
 int StatsTable::FindCounterOrEmptyRow(const std::string& name) const {
   // Note: the API returns slots numbered from 1..N, although
   // internally, the array is 0..N-1.  This is so that we can return
   // zero as "not found".
   //
   // There isn't much reason for this other than to be consistent
   // with the way we track columns for thread slots.  (See comments
   // in FindEmptyThread for why it is done this way).
-  if (!impl_)
+  if (!internal_)
     return 0;
 
   int free_slot = 0;
-  for (int index = 1; index <= impl_->max_counters(); index++) {
-    char* row_name = impl_->counter_name(index);
+  for (int index = 1; index <= internal_->max_counters(); index++) {
+    char* row_name = internal_->counter_name(index);
     if (!*row_name && !free_slot)
       free_slot = index;  // save that we found a free slot
     else if (!strncmp(row_name, name.c_str(), kMaxCounterNameLength))
       return index;
   }
   return free_slot;
 }
 
 int StatsTable::AddCounter(const std::string& name) {
-  if (!impl_)
+  if (!internal_)
     return 0;
 
   int counter_id = 0;
   {
     // To add a counter to the shared memory, we need the
     // shared memory lock.
-    SharedMemoryAutoLock lock(impl_->shared_memory());
+    SharedMemoryAutoLock lock(internal_->shared_memory());
 
     // We have space, so create a new counter.
     counter_id = FindCounterOrEmptyRow(name);
     if (!counter_id)
       return 0;
 
     std::string counter_name = name;
     if (name.empty())
       counter_name = kUnknownName;
-    strlcpy(impl_->counter_name(counter_id), counter_name.c_str(),
+    strlcpy(internal_->counter_name(counter_id), counter_name.c_str(),
             kMaxCounterNameLength);
   }
 
   // now add to our in-memory cache
   {
     AutoLock lock(counters_lock_);
     counters_[name] = counter_id;
   }
   return counter_id;
 }
 
 StatsTable::TLSData* StatsTable::GetTLSData() const {
   TLSData* data =
     static_cast<TLSData*>(tls_index_.Get());
   if (!data)
     return NULL;
 
   DCHECK(data->slot);
   DCHECK_EQ(data->table, this);
   return data;
 }
 
+#if defined(OS_POSIX)
+SharedMemoryHandle StatsTable::GetSharedMemoryHandle() const {
+  if (!internal_)
+    return SharedMemory::NULLHandle();
+  return internal_->shared_memory()->handle();
+}
+#endif
+
 }  // namespace base