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Busy-waiting itself can be made much less wasteful by using a delay function (e.g., sleep()) found in most operating systems. This puts a thread to sleep for a specified time, during which the thread will waste no CPU time. If the loop is checking something simple then it will spend most of its time asleep and will waste very little CPU time.
Sleep causes the thread or process to give up the remainder of its time slice and stay in the Not Runnable state for the specified duration. While there is generally a guarantee for the minimum time period, there is no strict guarantee that the thread will run immediately or soon, or even at all, once the specified time has passed.
In this way, there is a race condition between all the awakened threads. The first thread to run will win the race and find the condition satisfied, while the other threads will lose the race, and experience a spurious wakeup. [citation needed] The problem of spurious wakeup can be exacerbated on multiprocessor systems.
The result is an indefinite postponement until the thread holding the lock can finish and release it. This is especially true on a single-processor system, where each waiting thread of the same priority is likely to waste its quantum (allocated time where a thread can run) spinning until the thread that holds the lock is finally finished.
This is because the regular signal might wake up a thread of the wrong type whose condition has not yet been met, and that thread would go back to sleep without a thread of the correct type getting signaled. For example, a producer might make the queue full and wake up another producer instead of a consumer, and the woken producer would go back ...
lock contention: this occurs whenever one process or thread attempts to acquire a lock held by another process or thread. The more fine-grained the available locks, the less likely one process/thread will request a lock held by the other. (For example, locking a row rather than the entire table, or locking a cell rather than the entire row);
In this program, the thread barrier is defined as a struct, struct _thread_barrier, which include: total_thread: Total threads in the process; thread_barrier_number: Total number of threads expected to enter the thread barrier so that it can be lifted; lock: A POSIX thread mutex lock
POSIX Threads is an API defined by the Institute of Electrical and Electronics Engineers (IEEE) standard POSIX.1c, Threads extensions (IEEE Std 1003.1c-1995). Implementations of the API are available on many Unix-like POSIX-conformant operating systems such as FreeBSD , NetBSD , OpenBSD , Linux , macOS , Android [ 1 ] , Solaris , Redox , and ...