266 lines
7.2 KiB
Groff
266 lines
7.2 KiB
Groff
.\" Copyright (c) 2005 David Xu <davidxu@FreeBSD.org>
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice(s), this list of conditions and the following disclaimer as
|
|
.\" the first lines of this file unmodified other than the possible
|
|
.\" addition of one or more copyright notices.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice(s), this list of conditions and the following disclaimer in
|
|
.\" the documentation and/or other materials provided with the
|
|
.\" distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
|
|
.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
|
|
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
|
|
.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
|
.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
|
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
|
|
.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
|
|
.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
|
|
.\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
|
|
.\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd September 11, 2000
|
|
.Dt TIMER_SETTIME 2
|
|
.Os
|
|
.Sh NAME
|
|
.Nm timer_getoverrun ,
|
|
.Nm timer_gettime ,
|
|
.Nm timer_settime
|
|
.Nd "per-process timers (REALTIME)"
|
|
.Sh LIBRARY
|
|
.Lb librt
|
|
.Sh SYNOPSIS
|
|
.In time.h
|
|
.Ft int
|
|
.Fn timer_getoverrun "timer_t timerid"
|
|
.Ft int
|
|
.Fn timer_gettime "timer_t timerid" "struct itimerspec *value"
|
|
.Ft int
|
|
.Fo timer_settime
|
|
.Fa "timer_t timerid" "int flags" "const struct itimerspec *restrict value"
|
|
.Fa "struct itimerspec *restrict ovalue"
|
|
.Fc
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn timer_gettime
|
|
system call stores the amount of time until the specified timer,
|
|
.Fa timerid ,
|
|
expires and the reload value of the timer into the space pointed to by the
|
|
.Fa value
|
|
argument.
|
|
The
|
|
.Va it_value
|
|
member of this structure contains the amount of time
|
|
before the timer expires, or zero if the timer is disarmed.
|
|
This value is
|
|
returned as the interval until timer expiration, even if the timer was armed
|
|
with absolute time.
|
|
The
|
|
.Va it_interval
|
|
member of
|
|
.Fa value
|
|
contains the reload
|
|
value last set by
|
|
.Fn timer_settime .
|
|
.Pp
|
|
The
|
|
.Fn timer_settime
|
|
system call sets the time until the next expiration of the timer specified
|
|
by
|
|
.Fa timerid
|
|
from the
|
|
.Va it_value
|
|
member of the
|
|
.Fa value
|
|
argument and arms the timer if the
|
|
.Va it_value
|
|
member of
|
|
.Fa value
|
|
is non-zero.
|
|
If the specified timer was already
|
|
armed when
|
|
.Fn timer_settime
|
|
is called, this call resets the time until next expiration to the value
|
|
specified.
|
|
If the
|
|
.Va it_value
|
|
member of
|
|
.Fa value
|
|
is zero, the timer is disarmed.
|
|
If the timer is disarmed, then pending signal is removed.
|
|
.Pp
|
|
If the flag
|
|
.Dv TIMER_ABSTIME
|
|
is not set in the argument
|
|
.Fa flags ,
|
|
.Fn timer_settime
|
|
behaves as if the time until next expiration is set to
|
|
be equal to the interval specified by the
|
|
.Va it_value
|
|
member of
|
|
.Fa value .
|
|
That is,
|
|
the timer expires in
|
|
.Va it_value
|
|
nanoseconds from when the call is made.
|
|
If the flag
|
|
.Dv TIMER_ABSTIME
|
|
is set in the argument
|
|
.Fa flags ,
|
|
.Fn timer_settime
|
|
behaves as if the time until next expiration is set to be equal to the
|
|
difference between the absolute time specified by the it_value member of
|
|
value and the current value of the clock associated with
|
|
.Fa timerid .
|
|
That is, the timer expires when the clock reaches the value specified by the
|
|
.Va it_value
|
|
member of
|
|
.Fa value .
|
|
If the specified time has already passed, the
|
|
system call succeeds and the expiration notification is made.
|
|
.Pp
|
|
The reload value of the timer is set to the value specified by the
|
|
.Va it_interval
|
|
member of
|
|
.Fa value .
|
|
When a timer is armed with a non-zero
|
|
.Va it_interval ,
|
|
a periodic
|
|
(or repetitive) timer is specified.
|
|
.Pp
|
|
Time values that are between two consecutive non-negative integer multiples of
|
|
the resolution of the specified timer are rounded up to the larger multiple of
|
|
the resolution.
|
|
Quantization error will not cause the timer to expire earlier
|
|
than the rounded time value.
|
|
.Pp
|
|
If the argument
|
|
.Fa ovalue
|
|
is not
|
|
.Dv NULL ,
|
|
the
|
|
.Fn timer_settime
|
|
system call stores, in the location referenced by
|
|
.Fa ovalue ,
|
|
a value representing
|
|
the previous amount of time before the timer would have expired, or zero if the
|
|
timer was disarmed, together with the previous timer reload value.
|
|
Timers do not
|
|
expire before their scheduled time.
|
|
.Pp
|
|
Only a single signal is queued to the process for a given timer at any point in
|
|
time.
|
|
When a timer for which a signal is still pending expires, no signal is
|
|
queued, and a timer overrun will occur.
|
|
When a timer expiration signal is
|
|
accepted by a process, the
|
|
.Fn timer_getoverrun
|
|
system call returns the timer expiration overrun count for the specified timer.
|
|
The overrun count returned contains the number of extra timer expirations that
|
|
occurred between the time the signal was generated (queued) and when it was
|
|
accepted, up to but not including an maximum of
|
|
.Brq Dv DELAYTIMER_MAX .
|
|
If the number of
|
|
such extra expirations is greater than or equal to
|
|
.Brq Dv DELAYTIMER_MAX ,
|
|
then the overrun count is set to
|
|
.Brq Dv DELAYTIMER_MAX .
|
|
The value returned by
|
|
.Fn timer_getoverrun
|
|
applies to the most recent expiration signal acceptance for the timer.
|
|
If no
|
|
expiration signal has been delivered for the timer, the return value of
|
|
.Fn timer_getoverrun
|
|
is unspecified.
|
|
.Sh RETURN VALUES
|
|
If the
|
|
.Fn timer_getoverrun
|
|
system call succeeds, it returns the timer expiration overrun count as explained
|
|
above.
|
|
Otherwise the value \-1 is returned, and the global variable
|
|
.Va errno
|
|
is set to indicate the error.
|
|
.Pp
|
|
.Rv -std timer_gettime timer_settime
|
|
.Sh ERRORS
|
|
The
|
|
.Fn timer_settime
|
|
system call
|
|
will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EINVAL
|
|
A
|
|
.Fa value
|
|
structure specified a nanosecond value less than zero or greater than
|
|
or equal to 1000 million, and the
|
|
.Va it_value
|
|
member of that structure did not
|
|
specify zero seconds and nanoseconds.
|
|
.El
|
|
.Pp
|
|
These system calls may fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EINVAL
|
|
The
|
|
.Fa timerid
|
|
argument does not correspond to an ID returned by
|
|
.Fn timer_create
|
|
but not yet deleted by
|
|
.Fn timer_delete .
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fn timer_settime
|
|
system call may fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EINVAL
|
|
The
|
|
.Va it_interval
|
|
member of
|
|
.Fa value
|
|
is not zero and the timer was created with
|
|
notification by creation of a new thread
|
|
.Va ( sigev_sigev_notify
|
|
was
|
|
.Dv SIGEV_THREAD )
|
|
and a fixed stack address has been set in the thread attribute pointed to by
|
|
.Va sigev_notify_attributes .
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fn timer_gettime
|
|
and
|
|
.Fn timer_settime
|
|
system calls
|
|
may fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EFAULT
|
|
Any arguments point outside the allocated address space or there is a
|
|
memory protection fault.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr clock_getres 2 ,
|
|
.Xr timer_create 2 ,
|
|
.Xr siginfo 3
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn timer_getoverrun ,
|
|
.Fn timer_gettime ,
|
|
and
|
|
.Fn timer_settime
|
|
system calls conform to
|
|
.St -p1003.1-2004 .
|
|
.Sh HISTORY
|
|
Support for
|
|
.Tn POSIX
|
|
per-process timer first appeared in
|
|
.Fx 7.0 .
|