multithreading - -applicationDidBecomeActive`如何在两个单独的后台线程上同时调度？

我们正在发生一个奇怪的崩溃-现在我确定是什么原因造成的，但是我注意到的一件奇怪的事情是，所有崩溃日志在两个单独的后台线程上都有-applicationDidBecomeActive

Thread 5:
0   libsystem_kernel.dylib               0x00007fffaebac456 semaphore_wait_trap + 10
1   MyApp                               0x0000000107389da1 -[OutputManager(TechSmithCloud) reloadCloudDestinations] (OutputManager+TechSmithCloud.m:59)
2   MyApp                               0x000000010728c4b4 __44-[AppController applicationDidBecomeActive:]_block_invoke (AppController.m:696)
3   libdispatch.dylib                    0x00007fffaea57f5f _dispatch_call_block_and_release + 12
4   libdispatch.dylib                    0x00007fffaea4f128 _dispatch_client_callout + 8
5   libdispatch.dylib                    0x00007fffaea51099 _dispatch_root_queue_drain + 917
6   libdispatch.dylib                    0x00007fffaea50cb7 _dispatch_worker_thread3 + 99
7   libsystem_pthread.dylib              0x00007fffaec9b746 _pthread_wqthread + 1299
8   libsystem_pthread.dylib              0x00007fffaec9b221 start_wqthread + 13


Thread 13:
0   libsystem_kernel.dylib               0x00007fffaebac456 semaphore_wait_trap + 10
1   MyApp                               0x0000000107389da1 -[OutputManager(TechSmithCloud) reloadCloudDestinations] (OutputManager+TechSmithCloud.m:59)
2   MyApp                               0x000000010728c4b4 __44-[AppController applicationDidBecomeActive:]_block_invoke (AppController.m:696)
3   libdispatch.dylib                    0x00007fffaea57f5f _dispatch_call_block_and_release + 12
4   libdispatch.dylib                    0x00007fffaea4f128 _dispatch_client_callout + 8
5   libdispatch.dylib                    0x00007fffaea51099 _dispatch_root_queue_drain + 917
6   libdispatch.dylib                    0x00007fffaea50cb7 _dispatch_worker_thread3 + 99
7   libsystem_pthread.dylib              0x00007fffaec9b746 _pthread_wqthread + 1299
8   libsystem_pthread.dylib              0x00007fffaec9b221 start_wqthread + 13

而且我无法对此进行复制（我在-applicationDidBecomeActive中注销了一条语句，并且一次只能注销一次）

所以我不确定这是不可能的，还是一个实际的问题

也许是与信号量有关的事情？

这是代码：

- (void)applicationDidBecomeActive:(NSNotification *)aNotification
{
   dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^
                  {
                     [[OutputManager sharedOutputManager] reloadCloudDestinations];
                  });

}

编辑：
-reloadCloudDestinations的代码

-(void) reloadCloudDestinations
{
   [self setupCloudLibrary];
   TSCAccount* account = [TSCCloudServices activeAccount];
   if( account.status == TSCAccount_SignedIn )
   {
      dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
      __weak __typeof(self) weakSelf = self;

      @try
      {
         AFHTTPSessionManager *test = (AFHTTPSessionManager*)[(TSCAccountHTTPSession*)[self.libraryCore valueForKey:@"sessionManager"] valueForKey:@"httpClient"];
         NSLog(@"%@", test);
         [self.libraryCore destinationsWithActions:NEVER_TRANSLATE(@"publish,list") completionBlock:^(NSArray *destinations, NSError *error) {

            @try
            {
               if( error == nil )
               {
                  [weakSelf createButtonsForNewDestinationsNotAlreadyPresent:destinations];
               }
               else
               {
                  NSLog(@"destinationsWithBlock error: %@", error);
               }
            }
            @catch (NSException* exception)
            {
               NSLog(@"reloadCloudDestinations - destinationWithBlock completion - An exception was thrown %@", exception);
            }
            @finally
            {
              dispatch_semaphore_signal(semaphore);
            }
         }];

         dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
      }
      @catch (NSException* exception)
      {
         NSLog(@"reloadCloudDestinations - An exception was thrown %@", exception);
         dispatch_semaphore_signal(semaphore);
      }
   }
}

最佳答案

回溯具有符号__44-[AppController applicationDidBecomeActive:]_block_invoke。那不是-applicationDidBecomeActive:方法本身。它是编译器为-applicationDidBecomeActive:方法中显示的块生成的函数的名称。

阻止功能出现在后台线程中，因为您正在将其分派到除主队列之外的其他队列中。这不是问题，只是一个解释。

可能会出现多次，可能是因为您的应用程序处于活动状态，已退出活动状态，然后在整个生命周期中再次处于活动状态。每次它变为活动状态时，都会在主线程上调用-applicationDidBecomeActive:。那将把该块提交到全局并发队列，并假设存在可用的CPU核心和其他系统资源，然后它将在后台线程上执行。

一个悬而未决的问题是，为什么当崩溃发生时这些块仍在运行，而不是在短时间内完成。您没有显示-[OutputManager reloadCloudDestinations]的代码，因此很难知道。显然，它等待计数为零或更少的信号量。

关于multithreading - -applicationDidBecomeActive`如何在两个单独的后台线程上同时调度？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/41047732/