The Tor Browser: ipc/chromium/src/base/stats_table.cc@6474c204b198 (annotated)

ipc/chromium/src/base/stats_table.cc@6474c204b198 (annotated)

ipc/chromium/src/base/stats_table.cc

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 // Copyright (c) 2006-2008 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/stats_table.h"
 #include "base/logging.h"
 #include "base/platform_thread.h"
 #include "base/process_util.h"
 #include "base/scoped_ptr.h"
 #include "base/shared_memory.h"
 #include "base/string_piece.h"
 #include "base/string_util.h"
 #include "base/sys_string_conversions.h"
 #include "base/thread_local_storage.h"
 #if defined(OS_POSIX)
 #include "errno.h"
 #endif
 // The StatsTable uses a shared memory segment that is laid out as follows
 //
 // +-------------------------------------------+
 // | Version | Size | MaxCounters | MaxThreads |
 // +-------------------------------------------+
 // | Thread names table                        |
 // +-------------------------------------------+
 // | Thread TID table                          |
 // +-------------------------------------------+
 // | Thread PID table                          |
 // +-------------------------------------------+
 // | Counter names table                       |
 // +-------------------------------------------+
 // | Data                                      |
 // +-------------------------------------------+
 //
 // The data layout is a grid, where the columns are the thread_ids and the
 // rows are the counter_ids.
 //
 // If the first character of the thread_name is '\0', then that column is
 // empty.
 // If the first character of the counter_name is '\0', then that row is
 // empty.
 //
 // About Locking:
 // This class is designed to be both multi-thread and multi-process safe.
 // Aside from initialization, this is done by partitioning the data which
 // each thread uses so that no locking is required.  However, to allocate
 // the rows and columns of the table to particular threads, locking is
 // required.
 //
 // At the shared-memory level, we have a lock.  This lock protects the
 // shared-memory table only, and is used when we create new counters (e.g.
 // use rows) or when we register new threads (e.g. use columns).  Reading
 // data from the table does not require any locking at the shared memory
 // level.
 //
 // Each process which accesses the table will create a StatsTable object.
 // The StatsTable maintains a hash table of the existing counters in the
 // table for faster lookup.  Since the hash table is process specific,
 // each process maintains its own cache.  We avoid complexity here by never
 // de-allocating from the hash table.  (Counters are dynamically added,
 // but not dynamically removed).
 // In order for external viewers to be able to read our shared memory,
 // we all need to use the same size ints.
 COMPILE_ASSERT(sizeof(int)==4, expect_4_byte_ints);
 namespace {
 // An internal version in case we ever change the format of this
 // file, and so that we can identify our table.
 const int kTableVersion = 0x13131313;
 // The name for un-named counters and threads in the table.
 const char kUnknownName[] = "<unknown>";
 // Calculates delta to align an offset to the size of an int
 inline int AlignOffset(int offset) {
   return (sizeof(int) - (offset % sizeof(int))) % sizeof(int);
 }
 inline int AlignedSize(int size) {
   return size + AlignOffset(size);
 }
 // StatsTableTLSData carries the data stored in the TLS slots for the
 // StatsTable.  This is used so that we can properly cleanup when the
 // thread exits and return the table slot.
 //
 // Each thread that calls RegisterThread in the StatsTable will have
 // a StatsTableTLSData stored in its TLS.
 struct StatsTableTLSData {
   StatsTable* table;
   int slot;
 };
 }  // namespace
 // The StatsTablePrivate maintains convenience pointers into the
 // shared memory segment.  Use this class to keep the data structure
 // clean and accessible.
 class StatsTablePrivate {
  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 StatsTablePrivate based on expected size parameters, or
   // return NULL on failure.
   static StatsTablePrivate* New(const std::string& name, int size,
                                 int max_threads, int max_counters);
   base::SharedMemory* shared_memory() { return &shared_memory_; }
   // 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.
   StatsTablePrivate() {}
   // 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);
   base::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_;
 };
 // static
 StatsTablePrivate* StatsTablePrivate::New(const std::string& name,
                                           int size,
                                           int max_threads,
                                           int max_counters) {
   scoped_ptr<StatsTablePrivate> priv(new StatsTablePrivate());
   if (!priv->shared_memory_.Create(name, false, true, size))
     return NULL;
   if (!priv->shared_memory_.Map(size))
     return NULL;
   void* memory = priv->shared_memory_.memory();
   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);
   // We have a valid table, so compute our pointers.
   priv->ComputeMappedPointers(memory);
   return priv.release();
 }
 void StatsTablePrivate::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 StatsTablePrivate::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);
   thread_names_table_ = reinterpret_cast<char*>(data + offset);
   offset += sizeof(char) *
             max_threads() * StatsTable::kMaxThreadNameLength;
   offset += AlignOffset(offset);
   thread_tid_table_ = reinterpret_cast<PlatformThreadId*>(data + offset);
   offset += sizeof(int) * max_threads();
   offset += AlignOffset(offset);
   thread_pid_table_ = reinterpret_cast<int*>(data + offset);
   offset += sizeof(int) * max_threads();
   offset += AlignOffset(offset);
   counter_names_table_ = reinterpret_cast<char*>(data + offset);
   offset += sizeof(char) *
             max_counters() * StatsTable::kMaxCounterNameLength;
   offset += AlignOffset(offset);
   data_table_ = reinterpret_cast<int*>(data + offset);
   offset += sizeof(int) * max_threads() * max_counters();
   DCHECK_EQ(offset, size());
 }
 // We keep a singleton table which can be easily accessed.
 StatsTable* StatsTable::global_table_ = NULL;
 StatsTable::StatsTable(const std::string& name, int max_threads,
                        int max_counters)
     : impl_(NULL),
       tls_index_(SlotReturnFunction) {
   int table_size =
     AlignedSize(sizeof(StatsTablePrivate::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_ = StatsTablePrivate::New(name, table_size, max_threads, max_counters);
   // TODO(port): clean up this error reporting.
 #if defined(OS_WIN)
   if (!impl_)
     CHROMIUM_LOG(ERROR) << "StatsTable did not initialize:" << GetLastError();
 #elif defined(OS_POSIX)
   if (!impl_)
     CHROMIUM_LOG(ERROR) << "StatsTable did not initialize:" << strerror(errno);
 #endif
 }
 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_;
   // If we are the global table, unregister ourselves.
   if (global_table_ == this)
     global_table_ = NULL;
 }
 int StatsTable::RegisterThread(const std::string& name) {
   int slot = 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.
   {
     base::SharedMemoryAutoLock lock(impl_->shared_memory());
     slot = FindEmptyThread();
     if (!slot) {
       return 0;
     }
     DCHECK(impl_);
     // We have space, so consume a column in the table.
     std::string thread_name = name;
     if (name.empty())
       thread_name = kUnknownName;
     base::strlcpy(impl_->thread_name(slot), thread_name.c_str(),
                   kMaxThreadNameLength);
     *(impl_->thread_tid(slot)) = PlatformThread::CurrentId();
     *(impl_->thread_pid(slot)) = base::GetCurrentProcId();
   }
   // Set our thread local storage.
   StatsTableTLSData* data = new StatsTableTLSData;
   data->table = this;
   data->slot = slot;
   tls_index_.Set(data);
   return slot;
 }
 StatsTableTLSData* StatsTable::GetTLSData() const {
   StatsTableTLSData* data =
     static_cast<StatsTableTLSData*>(tls_index_.Get());
   if (!data)
     return NULL;
   DCHECK(data->slot);
   DCHECK_EQ(data->table, this);
   return data;
 }
 void StatsTable::UnregisterThread() {
   UnregisterThread(GetTLSData());
 }
 void StatsTable::UnregisterThread(StatsTableTLSData* data) {
   if (!data)
     return;
   DCHECK(impl_);
   // Mark the slot free by zeroing out the thread name.
   char* name = impl_->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.
   StatsTableTLSData* tls_data = static_cast<StatsTableTLSData*>(data);
   if (tls_data) {
     DCHECK(tls_data->table);
     tls_data->table->UnregisterThread(tls_data);
   }
 }
 int StatsTable::CountThreadsRegistered() const {
   if (!impl_)
     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);
     if (*name != '\0')
       count++;
   }
   return count;
 }
 int StatsTable::GetSlot() const {
   StatsTableTLSData* data = GetTLSData();
   if (!data)
     return 0;
   return data->slot;
 }
 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_)
     return 0;
   int index = 1;
   for (; index <= impl_->max_threads(); index++) {
     char* name = impl_->thread_name(index);
     if (!*name)
       break;
   }
   if (index > impl_->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_)
     return 0;
   int free_slot = 0;
   for (int index = 1; index <= impl_->max_counters(); index++) {
     char* row_name = impl_->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::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_)
     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::AddCounter(const std::string& name) {
   DCHECK(impl_);
   if (!impl_)
     return 0;
   int counter_id = 0;
   {
     // To add a counter to the shared memory, we need the
     // shared memory lock.
     base::SharedMemoryAutoLock lock(impl_->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;
     base::strlcpy(impl_->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;
 }
 int* StatsTable::GetLocation(int counter_id, int slot_id) const {
   if (!impl_)
     return NULL;
   if (slot_id > impl_->max_threads())
     return NULL;
   int* row = impl_->row(counter_id);
   return &(row[slot_id-1]);
 }
 const char* StatsTable::GetRowName(int index) const {
   if (!impl_)
     return NULL;
   return impl_->counter_name(index);
 }
 int StatsTable::GetRowValue(int index, int pid) const {
   if (!impl_)
     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)
       rv += row[slot_id];
   }
   return rv;
 }
 int StatsTable::GetRowValue(int index) const {
   return GetRowValue(index, 0);
 }
 int StatsTable::GetCounterValue(const std::string& name, int pid) {
   if (!impl_)
     return 0;
   int row = FindCounter(name);
   if (!row)
     return 0;
   return GetRowValue(row, pid);
 }
 int StatsTable::GetCounterValue(const std::string& name) {
   return GetCounterValue(name, 0);
 }
 int StatsTable::GetMaxCounters() const {
   if (!impl_)
     return 0;
   return impl_->max_counters();
 }
 int StatsTable::GetMaxThreads() const {
   if (!impl_)
     return 0;
   return impl_->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("")))
       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);
 }

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ipc/chromium/src/base/stats_table.cc@6474c204b198 (annotated)

ipc/chromium/src/base/stats_table.cc