Most likely, it will not because thread 1 has recently slept.
More specifically, if thread 1 unlocks the mutex while thread 2 is waiting for it, it makes thread 2 runnable but this does not force the scheduler to preempt thread 1 or make thread 2 run immediately. There is no FIFO guarantee for locking a mutex (for efficiency reasons).
A thread should not hold a mutex for more time than it does not own it, particularly not if it sleeps while holding the mutex. On another terminal to see the file /tmp/error.log tail -f /tmp/error.logĪnd no new lines are outputed from /tmp/error.log => We can find that both stdout and /tmp/error.log increase.
pthread nosleep 2> /tmp/error.log # No sleep is done when each thread acquires pthread_mutex_lock => We can find that /tmp/error.log will not increase. pthread sleep 2> /tmp/error.log # Each thread will sleep 1 second after it acquires pthread_mutex_lock Sleep some time\n", *idx) įprintf(fd, "Before pthread_mutex_unlock is called\n", *idx) įprintf(fd, "pthread_mutex_unlock is finisheded.\n", *idx) Static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER įprintf(fd, "\nBefore pthread_mutex_lock is called\n", *idx) įprintf(fd, "pthread_mutex_lock is finisheded. I have tested it on linux kernel (2.6.31) and (2.6.9). So we can check these two different output to see whether the thread is blocked. In the code, the 1st thread's output is directed to stdout, while the 2nd's is directed to stderr.
Pthread c sleep not declared code#
So my question is: is this a real problem or is there any bug in my code ? By Linux manual, sleep() is not prohibited when a pthread_mutex_t is acquired. This is a very strange behavior and I think maybe a potential serious issue. However, I find that after some time, one of the two threads will block on pthread_mutex_lock() forever, while the other thread works normal. C++ does not contain any built-in support for multithreaded applications.In my test program, I start two threads, each of them just do the following logic: 1) pthread_mutex_lock() Each part of such a program is called a thread, and each thread defines a separate path of execution. An initialized thread object represents an active thread of execution Such a thread object is joinable, and has a unique thread id.Ī multithreaded program contains two or more parts that can run concurrently. Similarly one may ask, how do threads work in C++?Ī thread of execution is a sequence of instructions that can be executed concurrently with other such sequences in multithreading environments, while sharing a same address space. To execute the run() method by a thread, pass an instance of M圜lass to a Thread in its constructor (A constructor in Java is a block of code similar to a method that's called when an instance of an object is created). Similarly, how do you create a thread? The easiest way to create a thread is to create a class that implements the Runnable interface. Moreover, how do you make a thread wait in C++? It launches three thread from the main function. This function makes the current thread wait until the thread identified by *this has finished executing. To wait for a thread use the std:: thread::join() function.
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