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In the Solaris implementation of condition variables, a spurious wakeup may occur without the condition being assigned if the process is signaled; the wait system call aborts and returns EINTR. [2] The Linux p-thread implementation of condition variables guarantees that it will not do that. [3] [4]
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
wait c, m, where c is a condition variable and m is a mutex (lock) associated with the monitor. This operation is called by a thread that needs to wait until the assertion P c is true before proceeding. While the thread is waiting, it does not occupy the monitor. The function, and fundamental contract, of the "wait" operation, is to do the ...
#include <pthread.h> #include <stdatomic.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> /* i is global, so it is visible to all functions. It makes use of the special * type atomic_int, which allows atomic memory accesses. */ atomic_int i = 0; /* f1 uses a spinlock to wait for i to change from 0. */ static void * f1 (void * p) {int local_i; /* Atomically load current value of i ...
Reentrancy is not the same thing as idempotence, in which the function may be called more than once yet generate exactly the same output as if it had only been called once. Generally speaking, a function produces output data based on some input data (though both are optional, in general). Shared data could be accessed by any function at any time.
As we can see from the source code, there are just only two threads are created. Those 2 thread both have thread_func(), as the thread function handler, which call pthread_barrier_wait (& barrier), while thread barrier expected 3 threads to call pthread_barrier_wait (THREAD_BARRIERS_NUMBER = 3) in order to be lifted. Change TOTAL_THREADS to 3 ...
Thread A calls function F which acquires a reentrant lock for itself before proceeding; Thread B calls function F which attempts to acquire a reentrant lock for itself but cannot due to one already outstanding, resulting in either a block (it waits), or a timeout if requested; Thread A's F calls itself recursively.
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.