The Tor Browser: media/libvpx/vp9/decoder/vp9_thread.c@ac0c01689b40 (annotated)

media/libvpx/vp9/decoder/vp9_thread.c@ac0c01689b40 (annotated)

media/libvpx/vp9/decoder/vp9_thread.c

Thu, 15 Jan 2015 15:59:08 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 15 Jan 2015 15:59:08 +0100
branch: TOR_BUG_9701
changeset 10: ac0c01689b40
permissions: -rw-r--r--

Implement a real Private Browsing Mode condition by changing the API/ABI;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 // Copyright 2013 Google Inc. All Rights Reserved.
 //
 // Use of this source code is governed by a BSD-style license
 // that can be found in the COPYING file in the root of the source
 // tree. An additional intellectual property rights grant can be found
 // in the file PATENTS. All contributing project authors may
 // be found in the AUTHORS file in the root of the source tree.
 // -----------------------------------------------------------------------------
 //
 // Multi-threaded worker
 //
 // Original source:
 //  http://git.chromium.org/webm/libwebp.git
 //  100644 blob eff8f2a8c20095aade3c292b0e9292dac6cb3587  src/utils/thread.c
 #include <assert.h>
 #include <string.h>   // for memset()
 #include "./vp9_thread.h"
 #if defined(__cplusplus) || defined(c_plusplus)
 extern "C" {
 #endif
 #if CONFIG_MULTITHREAD
 #if defined(_WIN32)
 //------------------------------------------------------------------------------
 // simplistic pthread emulation layer
 #include <process.h>  // NOLINT
 // _beginthreadex requires __stdcall
 #define THREADFN unsigned int __stdcall
 #define THREAD_RETURN(val) (unsigned int)((DWORD_PTR)val)
 static int pthread_create(pthread_t* const thread, const void* attr,
                           unsigned int (__stdcall *start)(void*), void* arg) {
   (void)attr;
   *thread = (pthread_t)_beginthreadex(NULL,   /* void *security */
 ,      /* unsigned stack_size */
                                       start,
                                       arg,
 ,      /* unsigned initflag */
                                       NULL);  /* unsigned *thrdaddr */
   if (*thread == NULL) return 1;
   SetThreadPriority(*thread, THREAD_PRIORITY_ABOVE_NORMAL);
   return 0;
 }
 static int pthread_join(pthread_t thread, void** value_ptr) {
   (void)value_ptr;
   return (WaitForSingleObject(thread, INFINITE) != WAIT_OBJECT_0 ||
           CloseHandle(thread) == 0);
 }
 // Mutex
 static int pthread_mutex_init(pthread_mutex_t* const mutex, void* mutexattr) {
   (void)mutexattr;
   InitializeCriticalSection(mutex);
   return 0;
 }
 static int pthread_mutex_lock(pthread_mutex_t* const mutex) {
   EnterCriticalSection(mutex);
   return 0;
 }
 static int pthread_mutex_unlock(pthread_mutex_t* const mutex) {
   LeaveCriticalSection(mutex);
   return 0;
 }
 static int pthread_mutex_destroy(pthread_mutex_t* const mutex) {
   DeleteCriticalSection(mutex);
   return 0;
 }
 // Condition
 static int pthread_cond_destroy(pthread_cond_t* const condition) {
   int ok = 1;
   ok &= (CloseHandle(condition->waiting_sem_) != 0);
   ok &= (CloseHandle(condition->received_sem_) != 0);
   ok &= (CloseHandle(condition->signal_event_) != 0);
   return !ok;
 }
 static int pthread_cond_init(pthread_cond_t* const condition, void* cond_attr) {
   (void)cond_attr;
   condition->waiting_sem_ = CreateSemaphore(NULL, 0, 1, NULL);
   condition->received_sem_ = CreateSemaphore(NULL, 0, 1, NULL);
   condition->signal_event_ = CreateEvent(NULL, FALSE, FALSE, NULL);
   if (condition->waiting_sem_ == NULL ||
       condition->received_sem_ == NULL ||
       condition->signal_event_ == NULL) {
     pthread_cond_destroy(condition);
     return 1;
   }
   return 0;
 }
 static int pthread_cond_signal(pthread_cond_t* const condition) {
   int ok = 1;
   if (WaitForSingleObject(condition->waiting_sem_, 0) == WAIT_OBJECT_0) {
     // a thread is waiting in pthread_cond_wait: allow it to be notified
     ok = SetEvent(condition->signal_event_);
     // wait until the event is consumed so the signaler cannot consume
     // the event via its own pthread_cond_wait.
     ok &= (WaitForSingleObject(condition->received_sem_, INFINITE) !=
            WAIT_OBJECT_0);
   }
   return !ok;
 }
 static int pthread_cond_wait(pthread_cond_t* const condition,
                              pthread_mutex_t* const mutex) {
   int ok;
   // note that there is a consumer available so the signal isn't dropped in
   // pthread_cond_signal
   if (!ReleaseSemaphore(condition->waiting_sem_, 1, NULL))
     return 1;
   // now unlock the mutex so pthread_cond_signal may be issued
   pthread_mutex_unlock(mutex);
   ok = (WaitForSingleObject(condition->signal_event_, INFINITE) ==
         WAIT_OBJECT_0);
   ok &= ReleaseSemaphore(condition->received_sem_, 1, NULL);
   pthread_mutex_lock(mutex);
   return !ok;
 }
 #else  // _WIN32
 # define THREADFN void*
 # define THREAD_RETURN(val) val
 #endif
 //------------------------------------------------------------------------------
 static THREADFN thread_loop(void *ptr) {    // thread loop
   VP9Worker* const worker = (VP9Worker*)ptr;
   int done = 0;
   while (!done) {
     pthread_mutex_lock(&worker->mutex_);
     while (worker->status_ == OK) {   // wait in idling mode
       pthread_cond_wait(&worker->condition_, &worker->mutex_);
     }
     if (worker->status_ == WORK) {
       vp9_worker_execute(worker);
       worker->status_ = OK;
     } else if (worker->status_ == NOT_OK) {   // finish the worker
       done = 1;
     }
     // signal to the main thread that we're done (for Sync())
     pthread_cond_signal(&worker->condition_);
     pthread_mutex_unlock(&worker->mutex_);
   }
   return THREAD_RETURN(NULL);    // Thread is finished
 }
 // main thread state control
 static void change_state(VP9Worker* const worker,
                          VP9WorkerStatus new_status) {
   // no-op when attempting to change state on a thread that didn't come up
   if (worker->status_ < OK) return;
   pthread_mutex_lock(&worker->mutex_);
   // wait for the worker to finish
   while (worker->status_ != OK) {
     pthread_cond_wait(&worker->condition_, &worker->mutex_);
   }
   // assign new status and release the working thread if needed
   if (new_status != OK) {
     worker->status_ = new_status;
     pthread_cond_signal(&worker->condition_);
   }
   pthread_mutex_unlock(&worker->mutex_);
 }
 #endif  // CONFIG_MULTITHREAD
 //------------------------------------------------------------------------------
 void vp9_worker_init(VP9Worker* const worker) {
   memset(worker, 0, sizeof(*worker));
   worker->status_ = NOT_OK;
 }
 int vp9_worker_sync(VP9Worker* const worker) {
 #if CONFIG_MULTITHREAD
   change_state(worker, OK);
 #endif
   assert(worker->status_ <= OK);
   return !worker->had_error;
 }
 int vp9_worker_reset(VP9Worker* const worker) {
   int ok = 1;
   worker->had_error = 0;
   if (worker->status_ < OK) {
 #if CONFIG_MULTITHREAD
     if (pthread_mutex_init(&worker->mutex_, NULL) ||
         pthread_cond_init(&worker->condition_, NULL)) {
       return 0;
     }
     pthread_mutex_lock(&worker->mutex_);
     ok = !pthread_create(&worker->thread_, NULL, thread_loop, worker);
     if (ok) worker->status_ = OK;
     pthread_mutex_unlock(&worker->mutex_);
 #else
     worker->status_ = OK;
 #endif
   } else if (worker->status_ > OK) {
     ok = vp9_worker_sync(worker);
   }
   assert(!ok || (worker->status_ == OK));
   return ok;
 }
 void vp9_worker_execute(VP9Worker* const worker) {
   if (worker->hook != NULL) {
     worker->had_error |= !worker->hook(worker->data1, worker->data2);
   }
 }
 void vp9_worker_launch(VP9Worker* const worker) {
 #if CONFIG_MULTITHREAD
   change_state(worker, WORK);
 #else
   vp9_worker_execute(worker);
 #endif
 }
 void vp9_worker_end(VP9Worker* const worker) {
   if (worker->status_ >= OK) {
 #if CONFIG_MULTITHREAD
     change_state(worker, NOT_OK);
     pthread_join(worker->thread_, NULL);
     pthread_mutex_destroy(&worker->mutex_);
     pthread_cond_destroy(&worker->condition_);
 #else
     worker->status_ = NOT_OK;
 #endif
   }
   assert(worker->status_ == NOT_OK);
 }
 //------------------------------------------------------------------------------
 #if defined(__cplusplus) || defined(c_plusplus)
 }    // extern "C"
 #endif

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media/libvpx/vp9/decoder/vp9_thread.c@ac0c01689b40 (annotated)

media/libvpx/vp9/decoder/vp9_thread.c