locking

I'm debating whether or not to move to a GCD-based pattern for multi-threaded accessors. I've been using custom lock-based synchronization in accessors for years, but I've found some info ( Intro to GCD ) and there seems to be pros of a GCD-based approach. I'm hoping to start a dialog here to help myself and others weigh the decision. The pattern looks like: - (id)something { __block id localSomething; dispatch_sync(queue, ^{ localSomething = [something retain]; }); return [localSomething autorelease]; } - (void)setSomething:(id)newSomething { dispatch_async(queue, ^{ if(newSomething !=

I've run into an innodb locking issue for transactions on a table with both a primary key and a separate unique index. It seems if a TX deletes a record using a unique key, and then re-inserts that same record, this will result in a next-key lock instead of the expected record lock (since the key is unique). See below for a test case as well as breakdown of what records I expect to have what locks: DROP TABLE IF EXISTS foo; CREATE TABLE `foo` ( `i` INT(11) NOT NULL, `j` INT(11) DEFAULT NULL, PRIMARY KEY (`i`), UNIQUE KEY `jk` (`j`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 ; INSERT INTO foo

Below is a list of locks that SQL Server 2000 is meant to support. I am a bit confused as to what the "intent" locks actually mean. I've looked around on the Web and the answers seem to be a bit cryptic. Further to getting an answer to my specific question, I am hoping to use this question as a Wiki for what each lock means and under what circumstances that type of lock will be acquired. Shared (S) Update (U) Exclusive (X) Intent intent shared (IS) intent exclusive (IX) shared with intent exclusive (SIX) intent update (IU) update intent exclusive (UIX) shared intent update (SIU) Schema schema

I'm building an ASP.NET MVC site where I want to use Lucene.Net for search. I've already built a SearchController and all of its methods, but I'm getting an error at runtime that occurs when the SearchController is first initialized. In SearchController, here's how I'm creating an IndexWriter: public static string IndexLocation = HostingEnvironment.MapPath("~/lucene"); public static Lucene.Net.Analysis.Standard.StandardAnalyzer analyzer = new Lucene.Net.Analysis.Standard.StandardAnalyzer(); public static IndexWriter writer = new IndexWriter(IndexLocation,analyzer); The error occurs on the last

I have a C# program that needs to perform a group of mass updates (20k+) to a SQL Server table. Since other users can update these records one at a time via an intranet website, we need to build the C# program with the capability of locking the table down. Once the table is locked to prevent another user from making any alterations/searches we will then need to preform the requested updates/inserts. Since we are processing so many records, we cannot use TransactionScope (seemed the easiest way at first) due to the fact our transaction winds up being handled by the MSDTC service . We need to

I have a multi threaded application that writes to a settings xml file using a static method. I want to avoid that the file is being updated twice at the same time (causing accesss/write exception). How do I do that? This doesn't work: namespace Program { public class Settings { private static void SetSettingsValue (string settings, string value) { // make this thread safe to avoid writing to a locked settings xml file lock (typeof(Settings)) { //write data to xml file } } } } The concept of lock() is to use an existing-object it can reference and use to control whether access is granted.

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: I am aware of locking concepts with synchronization of static and non static methods to lock classes and instances respectively. What I am not able to understand is, how is class level lock achieved? I mean, class is a template only, with no physical significance. So, when we say that class level locking is achieved with synchronizing static methods what happens then? Do all the objects of that class get locked or some other process? With what I could find out with my search is that there are class objects (Class.class) and lock is