rt_sem_wait.2

rtlinux(realtime linix)3.0,在kernel2.2.18上编译运行

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.TH RT_SEM_WAIT 2 "26 July 1997" "rt_ipc" "rt_ipc"
.SH NAME
rt_sem_wait \- semaphore 'wait' operation (with blocking)
.SH SYNOPSIS
.nf
.B #define MODULE
.B #include <linux/module.h> 
.B #include <linux/kernel.h> 
.B #include <linux/version.h> 
.B #include <linux/errno.h> 
.B #include "rt_ipc.h"
.fi
.sp
.BI "int rt_sem_wait(rt_sem_t *" sem ", RTIME " timeout ");
.SH DESCRIPTION
.B rt_sem_wait
is the semaphore wait (sometimes known as 'take' or 'P') operation.
Unlike with
.BR rt_sem_trywait ,
if the semaphore is not available, the calling task blocks until
it is.
.I sem
points to the structure used in the call to
.BR rt_sem_create .
An optional
.I timeout
can be specified.  If 
.I timeout
is RT_WAIT_FOREVER, the function does not time out.  If
.I timeout
is RT_NO_WAIT and the semaphore is not available,
.B rt_sem_wait
returns immediately.  If
.I timeout
is any other value, it represent a time at which the call to
.B rt_sem_wait
should time out.  If that time is reached,
.B rt_sem_wait
returns with -ETIME.
.SH "RETURN VALUE"
On success, 0 is returned.  On failure, a negative value is returned
as described below.
.SH ERRORS
.IP \fB-ETIME\fP
The timeout period expired.
.IP \fB-EINVAL\fP
.I sem
does not point to a valid rt_sem_t.
.SH "AUTHOR"
Jerry Epplin <[e-mail]>
.SH "SEE ALSO"
.BR rt_task_ipc_delete (2), 
.BR rt_task_ipc_init (2), 
.BR rt_sem_destroy (2), 
.BR rt_sem_init (2), 
.BR rt_sem_post (2),
.BR rt_sem_trywait (2)