Explanation: When you want to sleep a thread, condition variable can be used. In C under Linux, there is a function pthread_cond_wait () to wait or sleep. On the other hand, there is a function pthread_cond_signal () to wake up sleeping or waiting thread. Threads can wait on a condition variable.
How can a thread wait on a condition variable?
Explanation: When you want to sleep a thread, condition variable can be used. In C under Linux, there is a function pthread_cond_wait () to wait or sleep. On the other hand, there is a function pthread_cond_signal () to wake up sleeping or waiting thread. Threads can wait on a condition variable.
What are conditional wait and signal in multi-threading?
What are conditional wait and signal in multi-threading? Explanation: When you want to sleep a thread, condition variable can be used. In C under Linux, there is a function pthread_cond_wait () to wait or sleep. On the other hand, there is a function pthread_cond_signal () to wake up sleeping or waiting thread.
How to make one thread wait for the other to finish?
If one thread must wait for the other to finish, I see three options: Make the second thread do pthread_join () on the first one. Use a condition variable to signal the second thread when the first one is done. Stop using threads, as it's pointless to have one whose only job is to wait for another one.
How do I join two threads in a single thread?
Make the second thread do pthread_join () on the first one. Use a condition variable to signal the second thread when the first one is done. Stop using threads, as it's pointless to have one whose only job is to wait for another one. Just put the logic sequentially in a single thread.
How do you make a thread wait for some time?
In between, we have also put the main thread to sleep by using TimeUnit. sleep() method. So the main thread can wait for some time and in the meantime, T1 will resume and complete its execution.
What is pthread_join in C?
The pthread_join() function suspends execution of the calling thread until the target thread terminates, unless the target thread has already terminated.
How do you use conditional wait?
0:001:50Conditional Wait Variables - YouTubeYouTubeStart of suggested clipEnd of suggested clipChange is done to true. And then send a signal to anyone waiting on this condition a signal thatMoreChange is done to true. And then send a signal to anyone waiting on this condition a signal that they should wake up. And then he'll unlock the lock thread b for his part will first acquire the lock.
What happens when a thread is waiting?
A thread is in the waiting state when it wants to wait on a signal from another thread before proceeding. Once this signal is received, it becomes runnable. A thread moves to the blocked state when it wants to access an object that is being used (locked) by another thread.
Does pthread_join wait?
The pthread_join() function waits for the thread specified by thread to terminate. If that thread has already terminated, then pthread_join() returns immediately.
Do I need to call pthread_join?
Yes if thread is attachable then pthread_join is must otherwise it creates a Zombie thread.
Which variable allows you to apply a wait () over the process?
wait() takes the address of an integer variable and returns the process ID of the completed process. One of the main purposes of wait() is to wait for completion of child processes.
What is conditional variable in C?
A Join allows one thread to wait for another to complete but a condition variable allows any number of threads to wait for another thread to signal a condition.
What is condition variable in multithreading?
Condition Variable is a kind of Event used for signaling between two or more threads. One or more thread can wait on it to get signaled, while an another thread can signal this.
What is thread waiting state?
BLOCKED Vs WAITING States In Java :WAITINGBLOCKEDThe thread will be in this state when it calls wait() or join() method. The thread will remain in WAITING state until any other thread calls notify() or notifyAll() .The thread will be in this state when it is notified by other thread but has not got the object lock yet.2 more rows•Jun 1, 2016
Why wait () notify () and notifyAll are in object class?
If wait() and notify() were on the Thread instead then each thread would have to know the status of every other thread and there is no way to know thread1 that thread2 was waiting for any resource to access. Hence, notify, wait, notifyAll methods are defined in object class in Java.
How does thread go from waiting to runnable state?
When the method start() is invoked on a thread, the thread scheduler moves that thread to the runnable state. Whenever the join() method is invoked on any thread instance, the current thread executing that statement has to wait for this thread to finish its execution, i.e., move that thread to the terminated state.
What does pthread_join return?
Return Values pthread_join() returns zero when it completes successfully.
What is the difference between pthread_exit and pthread_join?
pthread_exit is called from the thread itself to terminate its execution (and return a result) early. pthread_join is called from another thread (usually the thread that created it) to wait for a thread to terminate and obtain its return value.
What is pthread_detach used for?
The pthread_detach() function is used to indicate to your application that storage for the thread tid can be reclaimed when the thread terminates. Threads should be detached when they are no longer needed. If tid has not terminated, pthread_detach() does not cause the thread to terminate.
Can a different thread call pthread_join?
Multiple threads cannot use pthread_join() to wait for the same target thread to end. If a thread issues pthread_join() for a target thread after another thread has successfully issued pthread_join() for the same target thread, the second pthread_join() will be unsuccessful.
What is thread_return?
thread_return: pointer to the location where the exit status of the thread mentioned in th is stored.
How do two threads of execution work?
Explanation: Here two threads of execution are created in the code. The order of the lines of output of the two threads may be interchanged depending upon the thread processed earlier. The main thread waits on the newly created thread for exiting. Therefore, the final line of the output is printed only after the new thread exits. The threads can terminate independently of each other by not using the pthread_join function. If we want to terminate the new thread manually, we may use pthread_cancel to do it.
What is POSIX thread?
In a Unix/Linux operating system, the C/C++ languages provide the POSIX thread (pthread) standard API (Application program Interface) for all thread related functions. It allows us to create multiple threads for concurrent process flow. It is most effective on multiprocessor or multi-core systems where threads can be implemented on a kernel-level for achieving the speed of execution. Gains can also be found in uni-processor systems by exploiting the latency in IO or other system functions that may halt a process.
Getting ready
To work through this recipe, you will need Visual Studio 2015. There are no other prerequisites. The source code for this recipe can be found at BookSamples\Chapter1\Recipe3.
How to do it..
To understand how a program waits for some computation in another thread to complete in order to use its result later, perform the following steps:
How it works..
When the program is run, it runs a long-running thread that prints out numbers and waits two seconds before printing each number. But, in the main program, we called the t.Join method, which allows us to wait for the thread t to complete working. When it is complete, the main program continues to run.
What does it mean when a thread is blocked from running?
When a thread is temporarily blocked from running, it calls Wait () This causes the thread to go to sleep and the lock for that object to be released, allowing another thread to use the object. At a later point, the sleeping thread is awakened when some other thread enters the same lock and calls Pulse () or PulseAll ().
Why does wait have to be before pulse?
Wait must execute before Pulse in order for the signal to work. If Pulse executes first, its pulse is lost, and the late waiter must wait for a fresh pulse, or remain forever blocked. This differs from the behavior of an AutoResetEvent, where its Set method has a "latching" effect and so is effective if called before WaitOne. ...
When to specify synchronizing object?
One must specify a synchronizing object when calling Wait or Pulse. If two threads use the same object, then they are able to signal each other. The synchronizing object must be locked prior to calling Wait or Pulse.
What is wait in C?
The wait () function in C is an operating system level call. Upon execution of the wait () function, the operating system blocks the calling process until one of its children returns or a signal is received. We can use this system call in our program when we need our process to wait for a few seconds for some task to finish. The syntax of the wait () system call is given below.
How to wait for a few seconds in C++?
For this purpose, there are two functions defined in C++ namely sleep_for () function and sleep_until () function. Let us see how we can use these functions to wait for a given number of seconds in C++.
What is delay function in C++?
Working of the delay () function is almost similar to the sleep () function. We can use the delay () function to make our programs wait for a few seconds in C++. The delay () function in c++ is defined in the ‘dos.h’ library. Therefore, it is mandatory to include this header file to use the delay function () in our program. The prototype of the delay function is given below.
What is wait system call?
The wait () system call is defined in the wait.h library. Therefore, we need to include the <sys/wait.h> header file in our program to use the wait () system call. The wait system call returns the child process id and also defines a pointer as its parameter that we can use to obtain the exit status of the child.
How long does a timer run in a loop?
In the loop, we then display the counter each time and then sleep for 1 second. This makes the timer run for 60 seconds.
Can DOS.h be compiled?
Caution: Since the ‘dos.h’ header file is only valid for DOS-based platforms, our program can only be compiled in the Turbo c++ environment. In other environments such as g++ Linux or equivalent windows environments, the above-written code file can not compile.
Can C++ create a timer?
C++ does not provide any inbuilt library to create a timer for our programs. However, we can create a timer event using system calls in C++. We will see how we can use the sleep () function in C++ to create timer events.
