keycode lock

Reprint: http://blog.csdn.net/sunp823/article/details/49886051The state of the lock: lock-free, biased, lightweight, and heavy-lock.The bias lock applies to scenarios where only one thread accesses the synchronization block.Lightweight locks, competing threads do not block, and are suitable for holding locks for a relatively short period of time. A thread that do

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:

I have never carefully understood the UPDATE lock. I recently saw a problem on the MSDN forum asking about the deadlock issue of heap table UPDATE. The problem is very simple. There are tables and data like this: Create table dbo. tb ( C1 int, C2 char (10 ), C3 varchar (10) ); GO DECLARE @ id int; SET @ id = 0; WHILE @ id BEGIN; SET @ id = @ id + 1; INSERT dbo. tb VALUES (@ id, 'B' + RIGHT (10000 + @ id, 4), 'C' + RIGHT (100000 + @ id, 4 )); END; Per

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

How to lock a row table database 1 how to lock a row of a table SET transaction isolation level read uncommitted Select * from Table rowlock where id = 1 2. Lock a table in the database Select * from table with (holdlock) Lock statement:SYBASE:Update table set col1 = col1 where 1 = 0;MSSQL:Select col1 from table (tabl

Redis Lock Structure and redis lockSingle thread and isolation Redis uses a single thread to execute transactions. transactions are run in a serial manner. That is to say, the execution of a single command in Redis and the execution of a transaction are thread-safe and will not affect each other, isolation. In multi-threaded programming, be careful when accessing shared resources: import threadingnum = 1lock = threading.Lock()def change_num(): glob

Original works, from "Deep Blue Blog" blog, dark blue blog:http://blog.csdn.net/huangyanlong/article/details/46876961RAC Production library kill lock table session killed state processing occursEnvironment:Operating system: CentOS 6.4 64BITDatabase: Oracle RAC 11.2.0.4 R2 64bitIn a project, when you perform a big data extraction task, the extraction error occurs and the large table needs to be re-extracted. The insert operation is canceled and then th

first, the encryption algorithm in AndroidThe previous article has introduced the Android System lock screen cipher algorithm principle, here to summarize said:The first type: input cipher algorithmEnter the plaintext password + The salt value of the device, then manipulate MD5 and SHA1 after the conversion to hex value for stitching, the final encryption information is saved to the local directory:/data/system/password.keyThe second type: gesture cip

The above discusses the mutex and conditional variables used for thread synchronization, this article will discuss the use of read and write locks and spin locks , and give the corresponding code and considerations, the relevant code can also be downloaded on my GitHub . read/write lock The mutex is either locked or unlocked, and only one thread can lock it at a time, while a read-write

Lock (Locking)In the process of implementing business logic, it is often necessary to guarantee the exclusivity of data access. As in the final settlement of the financial system, we want to process the data for a cut-off point in time, and we do not want the data to change again during the settlement process (which may be a few seconds or maybe a few hours). At this point, we need some mechanism to ensure that the data will not be modified in the pro

The recent accidental discovery before the pessimistic lock optimistic lock understanding is wrong, so re-study a bit.1. Pessimistic lockPessimistic lock Introduction (encyclopedia):Pessimistic locking, as its name implies, is a conservative attitude to the data being modified by the outside world (including other transactions currently in the system, as well as

In concurrent environments, you can consider the use of lock mechanisms when resolving shared resource conflict issues. 1. Object Lock All objects automatically contain a single lock. The JVM is responsible for tracking the number of times an object is locked. If an object is unlocked, its count becomes 0. When a task (thread) locks an object for the first time,

Java thread fair lock ReentrantLock (boolean fair), reentrantlock fair lockI. Fair lock 1. Why is there a fair lock? The CPU selects a thread randomly while waiting for the queue to schedule the thread. Because of this randomness, the thread cannot be guaranteed first-come-first-served (the lock controlled by synchroni

1. application. Lock and application. Unlock are usually paired to lock allCode(Do not lock the assignment to the application ). 2. Lock (OBJ) is used to lock the OBJ object. The OBJ object must be a global object (for example, application ). Application.

Lock, lock 1. view the current Lock ObjectSelect a. owner,A. object_name,B. xidusn,B. xidslot,B. xidsqn,B. session_id,B. oracle_username,B. OS _user_name,B. process,B. locked_mode,C. machine,C. status,C. server,C. sid,C. serial #,C. programFrom all_objects,V $ locked_object B,V $ session cWhere (a. object_id = B. object_id)And (B. process = c. process)Order by 1,

This article mainly introduced the PHP program in the file lock, mutual exclusion lock, read-write lock using skills analysis, which focuses on the Sync module and pthreads module use examples, the need for friends can refer to. We hope to help you. File lockFull name advisory file lock, which is mentioned in the book

Original: Lock-free data structure (LOCK-FREE data structures)One weeks ago, I wrote an article about the latch (latches) and spin lock (Spinlocks) in SQL Server. The 2 synchronization primitives (synchronization primitives) are used to protect shared data structures in SQL Server, such as pages in the cache pool (via a latch (latches)), and locks in the

1. PrefaceMultithreaded programming, we not only want to be able to achieve a logical sequencing between two threads, but also want to two unrelated threads when accessing the same resource, while only one thread can operate on the resources, otherwise there will be unpredictable results.For example, there are two threads need to add 1 to the same counter, we want the result is the counter finally add 2, but may also get to this counter, the first thread to the counter plus 1, but the second thr

, so to open a service to register, the service from the start and protect the job to do well. The basic implementation details are not much said, this article will only talk about a few difficulties encountered. Second, the difficulty in the realization of the lock screen 1. Screen Home key Since it is a lock screen interface, of course, only through the interface of some sliding or input action to unl

Another mechanism for implementing thread synchronization or mutual exclusion in Java 5 is the use of lock. Lock is more object-oriented than the synchronized method in the traditional threading model.Mutual-exclusion lock –lock (Reentrantlock)A mutex is a lock that can be h