Threading using C# and.Net

Сентябрь 7, 2022

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Threading using C# and.Net

Содержание

2. Outline : Threads System.Threading Namespace . Thread Class – its methods and properties. Thread Synchronization. Monitors
3. Threads : Thread is the fundamental unit of execution. More than one thread can be executing
4. With threads you can : Maintain a responsive user interface while background tasks are executing Distinguish
5. System.Threading Namespace Provides classes and interfaces that enable multithreaded programming. Consists of classes for synchronizing thread
6. Thread Class Implements various methods & properties that allows to manipulate concurrently running threads. Some of
7. Starting a thread : Thread thread = new Thread(new ThreadStart (ThreadFunc)); //Creates a thread object //
8. Suspending and Resuming Threads Thread.Suspend temporarily suspends a running thread. Thread.Resume will get it running again
9. Terminating a thread Thread.Abort() terminates a running thread. In order to end the thread , Abort()
10. A thread can prevent itself from being terminated with Thread.ResetAbort. - try{ … } catch(ThreadAbortException){ Thread.ResetAbort();
11. Thread Synchronization : Threads must be coordinated to prevent data corruption. Monitors Monitors allow us to
12. Void Method1() { …. Monitor.Enter(buffer); try { critical section; } finally { Monitor.Exit(buffer); } } Calls
13. The C # Lock Keyword : lock(buffer){ ……. } is equivalent to Monitor.Enter(buffer); try { critical
14. Reader/Writer locks : Prevent concurrent threads from accessing a resource simultaneously. Permit multiple threads to read
15. Drawback : Threads that need writer locks while they hold reader locks will result in deadlocks.
16. MethodImpl Attribute For synchronizing access to entire methods. To prevent a method from be executed by
17. Conclusion : Using more than one thread, is the most powerful technique available to increase responsiveness
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Слайд 2

Outline :
Threads
System.Threading Namespace .
Thread Class – its methods and properties.
Thread

Synchronization.
Monitors
C# Lock keyword.
Reader/Writer Locks
Conclusion

Слайд 3

Threads :
Thread is the fundamental unit of execution.
More than one

thread can be executing code inside the same process (application).
On a single-processor machine, the operating system is switching rapidly between the threads, giving the appearance of simultaneous execution.

Слайд 4

With threads you can :
Maintain a responsive user interface while

background tasks are executing
Distinguish tasks of varying priority
Perform operations that consume a large amount of time without stopping the rest of the application

Слайд 5

System.Threading Namespace
Provides classes and interfaces that enable multithreaded programming.
Consists of

classes for synchronizing thread activities .
Chief among the namespace members is Thread class

Слайд 6

Thread Class
Implements various methods & properties that allows to manipulate

concurrently running threads.
Some of them are :
CurrentThread
IsAlive
IsBackground
Name
Priority
ThreadState

Слайд 7

Starting a thread :
Thread thread = new Thread(new ThreadStart (ThreadFunc));
//Creates

a thread object
// ThreadStart identifies the method that the thread executes when it
//starts
thread.Start();
//starts the thread running
Thread Priorities :
Controls the amount of CPU time that can be allotted to a thread.
ThreadPriority.Highest
ThreadPriority.AboveNormal
ThreadPriority.Normal
ThreadPriority.BelowNormal
ThreadPriority.Lowest

Слайд 8

Suspending and Resuming Threads
Thread.Suspend temporarily suspends a running thread.
Thread.Resume will

get it running again
Sleep : A thread can suspend itself by calling Sleep.
Difference between Sleep and Suspend
- A thread can call sleep only on itself.
-Any thread can call Suspend on another thread.

Слайд 9

Terminating a thread
Thread.Abort() terminates a running thread.
In order to

end the thread , Abort() throws a ThreadAbortException.
Suppose a thread using SQL Connection ends prematurely , we can close the the SQL connection by placing it in the finally block.
- SqlConnection conn ………
try{
conn.open();
….
.....
}
finally{
conn.close();//this gets executed first before the thread ends.
}

Слайд 10

A thread can prevent itself from being terminated with Thread.ResetAbort.

- try{
…
}
catch(ThreadAbortException){
Thread.ResetAbort();
}
Thread.Join()
When one thread terminates another, wait for the other thread to end.

Слайд 11

Thread Synchronization :
Threads must be coordinated to prevent data corruption.
Monitors
Monitors

allow us to obtain a lock on a particular object and use that lock to restrict access to critical section of code.
While a thread owns a lock for an object, no other thread can acquire that lock.
Monitor.Enter(object) claims the lock but blocks if another thread already owns it.
Monitor.Exit(object) releases the lock.

Слайд 12

Void Method1()
{
….
Monitor.Enter(buffer);
try
{
critical section;
}
finally
{
Monitor.Exit(buffer);
}
}
Calls to Exit are enclosed in finally

blocks to ensure that they’re executed even when an exception arises.

Слайд 13

The C # Lock Keyword :
lock(buffer){
…….
}
is equivalent to
Monitor.Enter(buffer);
try
{
critical

section;
}
finally
{
Monitor.Exit(buffer);
}
- Makes the code concise.
- Also ensures the presence of a finally block to make sure the lock is released.

Слайд 14

Reader/Writer locks :
Prevent concurrent threads from accessing a resource simultaneously.
Permit

multiple threads to read concurrently.
Prevent overlapping reads and writes as well as
overlapping writes.
Reader function uses :
-AcquireReaderLock
-ReleaseReaderLock
Writer funciotn uses :
-AcquireReaderLock
-ReleaseReaderLock
ReleaseLocks are enclosed in finally blocks to be absolutely certain that they are executed

Слайд 15

Drawback :
Threads that need writer locks while they hold

reader locks will result in deadlocks.
Solution is UpgradeToWriterLock and DowngradeFromWriterLock methods.
rwlock.AcquireReaderLock(Timeout.Infinite)
try{
// read from the resource guarded by the lock
…..
//decide to do write to the resource
LockCookie cookie = rwlock.UpgradeToWriteLock(Timeout.Infinite)
try{
// write to the resource guarded by the lock
…..
}
finally{
rwlock.DowngradeFromWriterLock(ref cookie);
}
}
finally{
rwlock.ReleaseReaderLock();
}

Слайд 16

MethodImpl Attribute
For synchronizing access to entire methods.
To prevent a

method from be executed by more than one thread at a time ,
[MehtodImpl] (MethodImplOptions.Synchronized)]
Byte[] TransformData(byte[] buffer)
{
……
}
Only one thread at a time can enter the method.

Слайд 17

Conclusion :
Using more than one thread, is the most powerful

technique available to increase responsiveness to the user and process the data necessary to get the job done at almost the same time.

Threading using C# and.Net

Содержание

Outline :ThreadsSystem.Threading Namespace .Thread Class – its methods and properties.Thread

Threads :Thread is the fundamental unit of execution.More than one

With threads you can :Maintain a responsive user interface while

System.Threading NamespaceProvides classes and interfaces that enable multithreaded programming.Consists of

Thread ClassImplements various methods & properties that allows to manipulate

Starting a thread :Thread thread = new Thread(new ThreadStart (ThreadFunc));//Creates

Suspending and Resuming ThreadsThread.Suspend temporarily suspends a running thread.Thread.Resume will

Terminating a thread Thread.Abort() terminates a running thread.In order to

A thread can prevent itself from being terminated with Thread.ResetAbort.

Thread Synchronization :Threads must be coordinated to prevent data corruption.Monitors Monitors

Void Method1() { …. Monitor.Enter(buffer); try { critical section; } finally { Monitor.Exit(buffer); } }Calls to Exit are enclosed in finally

The C # Lock Keyword :lock(buffer){ ……. } is equivalent to Monitor.Enter(buffer); try { critical

Reader/Writer locks :Prevent concurrent threads from accessing a resource simultaneously.Permit

Drawback : Threads that need writer locks while they hold

MethodImpl Attribute For synchronizing access to entire methods.To prevent a

Conclusion :Using more than one thread, is the most powerful

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