synchronization

问题 I'm working on a bit of JavaScript that interacts with a client-side SQLite database, via the newish window.openDatabase(...) , database.transaction(...) and related APIs. As most of you know when you execute a query in this way it is an asynchronous call, which is typically good. You can make the call and handle the results as appropriate with callbacks. In my current situation I'm working on an algo for a client that does some hierarchy walking in the locally stored database. The part of

问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 6 years ago . What are the principles of a condition variable in synchronization of the processes of operating systems? 回答1: Well, conditional variables allow you to wait for certain condition to occur. In practice your thread may sleep on conditional variable and other thread wakes it up.

问题 If I have an unsynchronized java collection in a multithreaded environment, and I don't want to force readers of the collection to synchronize [1] , is a solution where I synchronize the writers and use the atomicity of reference assignment feasible? Something like: private Collection global = new HashSet(); // start threading after this void allUpdatesGoThroughHere(Object exampleOperand) { // My hypothesis is that this prevents operations in the block being re-ordered synchronized(global) {

问题 This question already has answers here : How to sync SQLite database on Android phone with MySQL database on server? (5 answers) Closed 6 years ago . I am building an Android app which will take some data and images from user and store them in a local SQLite DB. What i am looking forward to is a way by which i can replicate this DB to a MySQL DB on my server. I looked on the Internet for the answer but there isn't a proper solution to it. Though the most common answers i found were

问题 First a little context : I'm in the process of learning about threading in C++11 and for this purpose, I'm trying to build a small actor class, essentially (I left the exception handling and propagation stuff out) like so: class actor { private: std::atomic<bool> stop; private: std::condition_variable interrupt; private: std::thread actor_thread; private: message_queue incoming_msgs; public: actor() : stop(false), actor_thread([&]{ run_actor(); }) {} public: virtual ~actor() { // if the actor

问题 The press release of Android 2.0 states that the new release supports sync adapters so that emails and calendars cannot only be synced with gmail and exchange. However, there is no information available online how to write such a sync adapter. Has anyone tried it and some example code available? 回答1: These two articles by Sam Steele (January 23rd, 2010) are about the implementation of the last.fm sync adapter. Do not miss the second part and the opensource projects that are mentioned at the

问题 I am trying to make Event Syncing feature for a Project. I need to sync events with the remote server. Let's say I Installed the App in Device A. If I login to another device lets take B, then events synced from A should also appear in Device B, and events of B should also be synced. Now if I again login into the Device A, Events of B should be added. But events previously from A should not again be added to Device A again For this I decided to keep its eventIdentifier on the remote database.

问题 It is said that you should only call asynchronous-safe functions inside a signal handler. My question is, what constitutes asynchronous-safeness ? A function which is both reentrant and thread safe is asynchronous-safe I guess? Or No? 回答1: Re-entrance and thread safety has a little or nothing to do with this. Side effects, state and interruption of those functions are facts that matter. asynchronous-safe function [GNU Pth] A function is asynchronous-safe, or asynchronous-signal safe, if it

问题 In a nice article with some concurrency tips, an example was optimized to the following lines: double getBalance() { Account acct = verify(name, password); synchronized(acct) { return acct.balance; } } If I understand that correctly, the point of the synchronization is to ensure that the value of acct.balance that are read by this thread is current and that any pending writes to the fields of the object in acct.balance are also written to main memory. The example made me think a little:

问题 I have an application where 2 threads are running... Is there any certanty that when I change a global variable from one thread, the other will notice this change? I don't have any syncronization or Mutual exclusion system in place... but should this code work all the time (imagine a global bool named dataUpdated ): Thread 1: while(1) { if (dataUpdated) updateScreen(); doSomethingElse(); } Thread 2: while(1) { if (doSomething()) dataUpdated = TRUE; } Does a compiler like gcc optimize this