kiosk lock

Tag: Code member jdk1.7 read illegal boolean return port OwnerRelease Fair Lock (based on jdk1.7.0_40)1. Unlock ()Unlock () implemented in Reentrantlock.java, the source code is as follows: Public void unlock () { sync.release (1);}Description :Unlock () is an unlock function, which is implemented by Aqs's release () function.Here, the meaning of "1" is the same as the "Get Lock function acquire (1)", wh

"Why do you want to lock?" A database is a shared resource that is used by a multi-user, such as a user table T_user, two people in front of the browser login to the same account, the phone number changed. When multiple users have concurrent access to the data, multiple transactions are generated in the database while the same data is being accessed. If the concurrency operation is not controlled, it may read and store incorrect data, destroy the cons

have not been seriously understood UPDATE operation of the lock, recently in MSDN Forums See a problem, ask the heap table update deadlock problem, the problem is very simple, there are similar tables and data: CREATE TABLE DBO.TB ( C1 int, C2 char (Ten), c3 varchar) ; GO DECLARE @id int; SET @id = 0; While @id In query one, perform the update operation: BEGIN TRAN UPDATE dbo.tb SET c2 = ' xx ' WHERE c1 = 2; WAITFOR DELAY ' 00:00:30

1, Pessimistic lock It refers to the data by the external modification to maintain a conservative attitude, because, in the whole process of data processing, the card lock state. Pessimistic lock implementation, often rely on the database provides the lock mechanism (also only the database layer

Today, I see an article that describes in detail the concept of lock and lock granularity, and why should I lock it as follows? Locking is designed to prevent the confusion of different threads from accessing the same shared resource.A metaphor: People are different threads, toilets are shared resourcesWhen you are in the bathroom, you must

Optimistic lock Optimistic lock (optimistic lock), as the name implies, is very optimistic, every time to take the data when they think others will not be modified, so will not be locked, but in the update will be judged in the period when others have to update this data, you can use the version number and other mechanisms. Optimistic locking is useful for multi

Reference article: http://blog.csdn.net/chen77716/article/details/6618779There are two kinds of locking mechanisms in Java: The synchronized and Lock,lock interfaces and their implementation classes are JDK5 additions, and the author is the famous concurrency expert Doug Lea. This article does not compare synchronized with lock which is inferior, just introduces

first, the noun explanation1, pessimistic Lock: think every time the operation of the database (query, modify) is not safe, so each operation will be the data lock off, until the operation is finished releasing the lock2, Optimistic Lock: query data is always considered to be safe, will not lock the data, wait until th

Mysql lock mechanism usage summary, mysql Lock Mechanism 1. isolation level (1) Read uncommitted (RU) At this isolation level, transactions are completely isolated and dirty reads are generated. uncommitted records can be read, which is not used in actual cases. (2) Read committed (RC) Only committed records can be read. At this isolation level, phantom read occurs. Phantom read refers to executing the same

There are many implementation classes of lock in the Java.util.concurrent.locks package, commonly used in Reentrantlock, Readwritelock (Implementation class Reentrantreadwritelock), Its realization all relies on Java.util.concurrent.AbstractQueuedSynchronizer class, realizes the idea to be similar, therefore we take reentrantlock as the explanation cut-in point. 1. Reentrantlock's call Process After observation Reentrantlock all

Tags: handle dirty \ n Client pre Opera read data reporting requestThe lock in MySQL:Grammar:LOCK Table table Name 1 read| WRITE, table name 2 read| WRITE ... "Lock-up table" ... "..".UNLOCK TABLES "Release table"READ: Reading Lock | Shared Lock: All clients can only read this table and cannot write this tableWrite:

 Keywords:no-lock interlocked lock-free TCP/IP server engine IOCP server out-of-orderexecution no lock atomic Lock atomic operation Atomic Instruction lock independent open lock Communication Server engine high concurrency Big D

The typical page-level representative engine is BDB. The typical representative engine for the table level is myisam,memory and ISAM, a long time ago. The typical line-level representative engine is InnoDB. -the most used in our actual application is the row lock. The advantages of row-level locks are as follows: 1. Reduce lock state when many connections have different queries. 2), if there is an exception

Basic concepts In this chapter, we will explain the principle of "thread gain fair lock", and we need to understand several basic concepts before we explain it. The following are all based on these concepts; These concepts may be tedious, but from these concepts it is possible to glimpse some of the architecture of the "Java Lock", which is helpful in understanding the

Cost of LocksThe cost of locking is huge, especially for multicore multi-processing.The introduction of multi-processing, itself is to be parallelized processing to improve performance, however, because of the existence of a shared critical section, and this critical section can only have one thread access (especially for write operations), then the parallel execution flow is serialized here, visually, here seems to be a bottleneck on the Broad Road, Because serialization is inherently present,

Lock lock is an object-oriented locking scheme used by java5 instead of synchronized1 Public classLockdemo {2 /**3 * Lock is used to replace synchronized, with the advantage that lock is more object-oriented. Eclipse view interface for all implementation classes with Ctrl+t4 */5 6 Public Static voidMain

Exclusive Lock Concept:Exclusive Locks, known as X-Lock, write-lock, exclusive-lock. If a thing T1 a data object O1 with exclusive locks, only the transaction T1 read and write to the O1 during the entire lock-up, and other transactions must wait until the T1 releases the

The theoretical knowledge is boring, but these are basic skills and may be forgotten after learning. However, when used, we will find that the previous learning is very meaningful, and the learning thread is like this. 1. how to Create a lock? Lock lock = new ReentrantLock (); 2. How to Use the Lock? See the

-Weak consistency of Concurrenthashmap-Weak consistency of Synchronousqueue-Weak consistency of exchanger-Weak consistency of the Linux kernel lock-free queues– Summary Through the previous series of source analysis, we basically covered all the components of the JUC package. In many of these components, we always see a shadow of something: CAS. Quite a lock, its atomic particle size is smaller, it only act

level, will see, the effect is 1 seconds to insert a record into the Trantest table, for 30 seconds Create proc [dbo].[Testtrans] as begin Declare @timeSpan datetime Declare @timeStart datetime Declare @val int = 1 beginTrybegin Transaction Set @timeSpan = GETDATE();Set @timeStart=getdate(); while(DATEDIFF(Second,@timeStart,getdate()) -) begin while(DATEDIFF(SECOND,@timeSpan,getdate())=1) begin Set @timeSpan =