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cv_signal.9freebsd

Langue: en

Autres versions - même langue

Version: 328783 (ubuntu - 08/07/09)

Section: 9 (Appels noyau Linux)


BSD mandoc

NAME

condvar cv_init cv_destroy cv_wait cv_wait_sig cv_wait_unlock cv_timedwait cv_timedwait_sig cv_signal cv_broadcast cv_broadcastpri cv_wmesg - kernel condition variable

SYNOPSIS

In sys/param.h In sys/proc.h In sys/condvar.h Ft void Fn cv_init struct cv *cvp const char *desc Ft void Fn cv_destroy struct cv *cvp Ft void Fn cv_wait struct cv *cvp lock Ft int Fn cv_wait_sig struct cv *cvp lock Ft void Fn cv_wait_unlock struct cv *cvp lock Ft int Fn cv_timedwait struct cv *cvp lock int timo Ft int Fn cv_timedwait_sig struct cv *cvp lock int timo Ft void Fn cv_signal struct cv *cvp Ft void Fn cv_broadcast struct cv *cvp Ft void Fn cv_broadcastpri struct cv *cvp int pri Ft const char * Fn cv_wmesg struct cv *cvp

DESCRIPTION

Condition variables are used in conjunction with mutexes to wait for conditions to occur. Condition variables are created with Fn cv_init , where Fa cvp is a pointer to space for a Vt struct cv , and Fa desc is a pointer to a null-terminated character string that describes the condition variable. Condition variables are destroyed with Fn cv_destroy . Threads wait on condition variables by calling Fn cv_wait , Fn cv_wait_sig , Fn cv_wait_unlock , Fn cv_timedwait , or Fn cv_timedwait_sig . Threads unblock waiters by calling Fn cv_signal to unblock one waiter, or Fn cv_broadcast or Fn cv_broadcastpri to unblock all waiters. In addition to waking waiters, Fn cv_broadcastpri ensures that all of the waiters have a priority of at least Fa pri by raising the priority of any threads that do not. Fn cv_wmesg returns the description string of Fa cvp , as set by the initial call to Fn cv_init .

The Fa lock argument is a pointer to either a mutex(9), rwlock(9), or sx(9) lock. A mutex(9) argument must be initialized with MTX_DEF and not MTX_SPIN A thread must hold Fa lock before calling Fn cv_wait , Fn cv_wait_sig , Fn cv_wait_unlock , Fn cv_timedwait , or Fn cv_timedwait_sig . When a thread waits on a condition, Fa lock is atomically released before the thread is blocked, then reacquired before the function call returns. The Fn cv_wait_unlock function does not reacquire the lock before returning. All waiters must pass the same Fa lock in conjunction with Fa cvp .

When Fn cv_wait , Fn cv_wait_sig , Fn cv_wait_unlock , Fn cv_timedwait , and Fn cv_timedwait_sig unblock, their calling threads are made runnable. Fn cv_timedwait and Fn cv_timedwait_sig wait for at most Fa timo / HZ seconds before being unblocked and returning Er EWOULDBLOCK ; otherwise, they return 0. Fn cv_wait_sig and Fn cv_timedwait_sig return prematurely with a value of Er EINTR or Er ERESTART if a signal is caught, or 0 if signaled via Fn cv_signal or Fn cv_broadcast .

RETURN VALUES

If successful, Fn cv_wait_sig , Fn cv_timedwait , and Fn cv_timedwait_sig return 0. Otherwise, a non-zero error code is returned.

Fn cv_wmesg returns the description string that was passed to Fn cv_init .

ERRORS

Fn cv_wait_sig and Fn cv_timedwait_sig will fail if:
Bq Er EINTR
A signal was caught and the system call should be interrupted.
Bq Er ERESTART
A signal was caught and the system call should be restarted.

Fn cv_timedwait and Fn cv_timedwait_sig will fail if:

Bq Er EWOULDBLOCK
Timeout expired.

SEE ALSO

locking(9), mtx_pool9, mutex(9), rwlock(9), sema(9), sleep(9), sx(9)
Theoreme de Bowie:
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