sema_trywait(SYNCH)

sema_trywait -- conditionally claim resources under the semaphore's control

Synopsis

   cc [options] -Kthread file
   
   #include <synch.h>
   

   int sema_trywait(sema_t *sema);

Description

sema_trywait makes a single attempt to acquire the semaphore pointed to by sema. If the semaphore is available, sema_trywait decrements the semaphore value and returns to the caller.

If sema_trywait cannot immediately acquire the semaphore, it returns EBUSY to the caller, it does not block the caller to wait for the semaphore or decrement the semaphore value.

Parameters

sema: pointer to the semaphore to acquire

sema parameter

sema must have been previously initialized, either by sema_init or statically (see sema_init(SYNCH)).

Usage

sema_trywait is used when the caller does not want to block if the semaphore is unavailable.

Return values

sema_trywait returns zero for success and an error number for failure.

Errors

If the following condition occurs, sema_trywait fails and returns the corresponding value:

EBUSY: the semaphore cannot be acquired immediately

If the following condition is detected, sema_trywait returns the corresponding value:

EINVAL: invalid argument specified

References

Intro(SYNCH), semaphore(SYNCH), sema_destroy(SYNCH), sema_init(SYNCH), sema_post(SYNCH), sema_wait(SYNCH)