Sistemi operativi - Syscall pthread_cond_signal

Esame Sistemi operativi

Facoltà Ingegneria

Università Università degli studi di Napoli Federico II

Appunto

Appunti di sistemi operativi per l'esame dei professori Cotroneo e Natella. gli argomenti trattati sono i seguenti: System call pthread_cond_signal: name, sypnosis, description, return value, errors, examples, application usage, future directions, see also, derivation.

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pthread_cond_signal, pthread_cond_broadcast

The Single UNIX ® Specification, Version 2

NAME

pthread_cond_signal, pthread_cond_broadcast - signal or broadcast a condition

SYNOPSIS

#include <pthread.h>
int pthread_cond_signal(pthread_cond_t *cond);
int pthread_cond_broadcast(pthread_cond_t *cond);

DESCRIPTION

These two functions are used to unblock threads blocked on a condition variable.

The pthread_cond_signal() call unblocks at least one of the threads that are blocked on the specified condition variable cond (if any threads are blocked on cond).

The pthread_cond_broadcast() call unblocks all threads currently blocked on the specified condition variable cond.

If more than one thread is blocked on a condition variable, the scheduling policy determines the order in which threads are unblocked. When each thread unblocked as a result of a pthread_cond_signal() or pthread_cond_broadcast() returns from its call


topthread_cond_wait() or pthread_cond_timedwait(), the thread owns the mutex with which it called pthread_cond_wait() or pthread_cond_timedwait(). The thread(s) that are unblocked contend for the mutex according to the scheduling policy (if applicable), and as if each had called pthread_mutex_lock().

The pthread_cond_signal() or pthread_cond_broadcast() functions may be called by a thread whether or not it currently owns the mutex that threads calling pthread_cond_wait() or pthread_cond_timedwait() have associated with the condition variable during their waits; however, if predictable scheduling behaviour is required, then that mutex is locked by the thread calling pthread_cond_signal() or pthread_cond_broadcast().

The pthread_cond_signal() and pthread_cond_broadcast() functions have no effect if there are no threads currently blocked on cond.

RETURN VALUE
If successful, the pthread_cond_signal() and pthread_cond_broadcast() functions return zero. Otherwise, an error number is returned to indicate.

the error.

ERRORS

The pthread_cond_signal() and pthread_cond_broadcast() function may fail if:

[EINVAL] The value cond does not refer to an initialised condition variable.

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Dettagli

Publisher

N. A.

A.A. 2012-2013

2 pagine

SSD Scienze matematiche e informatiche INF/01 Informatica

I contenuti di questa pagina costituiscono rielaborazioni personali del Publisher N. A. di informazioni apprese con la frequenza delle lezioni di Sistemi operativi e studio autonomo di eventuali libri di riferimento in preparazione dell'esame finale o della tesi. Non devono intendersi come materiale ufficiale dell'università Università degli studi di Napoli Federico II o del prof Cotroneo Domenico.