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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.
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pthreads defines a set of C programming language types, functions and constants. It is implemented with a pthread.h header and a thread library. There are around 100 threads procedures, all prefixed pthread_ and they can be categorized into five groups: Thread management – creating, joining threads etc. Mutexes; Condition variables
As soon as the first thread in question is switched back to, its program counter will be at step 1c, and it will sleep and be unable to be woken up again, violating the invariant that it should have been on c's sleep-queue when it slept. Other race conditions depend on the ordering of steps 1a and 1b, and depend on where a context switch occurs.
The functions pthread_key_create and pthread_key_delete are used respectively to create and delete a key for thread-specific data. The type of the key is explicitly left opaque and is referred to as pthread_key_t. This key can be seen by all threads. In each thread, the key can be associated with thread-specific data via pthread_setspecific.
In the following piece of C code, the function is thread-safe, but not reentrant: # include <pthread.h> int increment_counter () { static int counter = 0 ; static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER ; // only allow one thread to increment at a time pthread_mutex_lock ( & mutex ); ++ counter ; // store value before any other ...
Like LinuxThreads, NPTL is a 1:1 threads library. Threads created by the library (via pthread_create) correspond one-to-one with schedulable entities in the kernel (processes, in the Linux case). [4]: 226 This is the simplest of the three threading models (1:1, N:1, and M:N).
The sleep() function call can be repeatedly called for short periods of time to slow the execution of a running program or code. Throttling code in this manner provides a coarse mechanism for mitigating the effects of overheating hardware [7] or easing timing issues for legacy programs. The downside to cycling sleep and running states rather ...