timerfd: Add manual page.
This manual page accompanies the timerfd system calls. Reviewed by: imp Differential Revision: https://reviews.freebsd.org/D40218
This commit is contained in:
parent
af93fea710
commit
8544651dc5
@ -345,6 +345,7 @@ MAN+= abort2.2 \
|
||||
timer_create.2 \
|
||||
timer_delete.2 \
|
||||
timer_settime.2 \
|
||||
timerfd.2 \
|
||||
truncate.2 \
|
||||
umask.2 \
|
||||
undelete.2 \
|
||||
@ -496,6 +497,9 @@ MLINKS+=symlink.2 symlinkat.2
|
||||
MLINKS+=syscall.2 __syscall.2
|
||||
MLINKS+=timer_settime.2 timer_getoverrun.2 \
|
||||
timer_settime.2 timer_gettime.2
|
||||
MLINKS+=timerfd.2 timerfd_create.2 \
|
||||
timerfd.2 timerfd_gettime.2 \
|
||||
timerfd.2 timerfd_settime.2
|
||||
MLINKS+=thr_kill.2 thr_kill2.2
|
||||
MLINKS+=truncate.2 ftruncate.2
|
||||
MLINKS+=unlink.2 unlinkat.2
|
||||
|
340
lib/libc/sys/timerfd.2
Normal file
340
lib/libc/sys/timerfd.2
Normal file
@ -0,0 +1,340 @@
|
||||
.\" SPDX-License-Identifier: BSD-2-Clause
|
||||
.\"
|
||||
.\" Copyright (c) 2023 Jake Freeland <jfree@FreeBSD.org>
|
||||
.\"
|
||||
.\" 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, this list of conditions and the following disclaimer.
|
||||
.\" 2. Redistributions in binary form must reproduce the above copyright
|
||||
.\" notice, 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 AUTHOR AND CONTRIBUTORS ``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 AUTHOR OR CONTRIBUTORS 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.
|
||||
.\"
|
||||
.Dd May 21, 2023
|
||||
.Dt TIMERFD 2
|
||||
.Os
|
||||
.Sh NAME
|
||||
.Nm timerfd ,
|
||||
.Nm timerfd_create ,
|
||||
.Nm timerfd_gettime ,
|
||||
.Nm timerfd_settime
|
||||
.Nd timers with file descriptor semantics
|
||||
.Sh LIBRARY
|
||||
.Lb libc
|
||||
.Sh SYNOPSIS
|
||||
.In sys/timerfd.h
|
||||
.Ft int
|
||||
.Fo timerfd_create
|
||||
.Fa "int clockid"
|
||||
.Fa "int flags"
|
||||
.Fc
|
||||
.Ft int
|
||||
.Fo timerfd_gettime
|
||||
.Fa "int fd"
|
||||
.Fa "struct itimerspec *curr_value"
|
||||
.Fc
|
||||
.Ft int
|
||||
.Fo timerfd_settime
|
||||
.Fa "int fd"
|
||||
.Fa "int flags"
|
||||
.Fa "const struct itimerspec *new_value"
|
||||
.Fa "struct itimerspec *old_value"
|
||||
.Fc
|
||||
.Sh DESCRIPTION
|
||||
The
|
||||
.Nm
|
||||
system calls operate on timers, identified by special
|
||||
.Nm
|
||||
file descriptors.
|
||||
These calls are analogous to
|
||||
.Fn timer_create ,
|
||||
.Fn timer_gettime ,
|
||||
and
|
||||
.Fn timer_settime
|
||||
per-process timer functions, but use a
|
||||
.Nm
|
||||
descriptor in place of
|
||||
.Fa timerid .
|
||||
.Pp
|
||||
All
|
||||
.Nm
|
||||
descriptors possess traditional file descriptor semantics; they may be passed
|
||||
to other processes, preserved across
|
||||
.Xr fork 2 ,
|
||||
and monitored via
|
||||
.Xr kevent 2 ,
|
||||
.Xr poll 2 ,
|
||||
or
|
||||
.Xr select 2 .
|
||||
When a
|
||||
.Nm
|
||||
descriptor is no longer needed, it may be disposed of using
|
||||
.Xr close 2 .
|
||||
.Bl -tag -width "Fn timerfd_settime"
|
||||
.It Fn timerfd_create
|
||||
Initialize a
|
||||
.Nm
|
||||
object and return its file descriptor.
|
||||
The
|
||||
.Fa clockid
|
||||
argument specifies the clock used as a timing base and may be:
|
||||
.Pp
|
||||
.Bl -tag -width "Dv CLOCK_MONOTONIC" -compact
|
||||
.It Dv CLOCK_REALTIME
|
||||
Increments as a wall clock should.
|
||||
.It Dv CLOCK_MONOTONIC
|
||||
Increments monotonically in SI seconds.
|
||||
.El
|
||||
.Pp
|
||||
The
|
||||
.Fa flags
|
||||
argument may contain the result of
|
||||
.Em or Ns 'ing
|
||||
the following values:
|
||||
.Pp
|
||||
.Bl -tag -width "Dv TFD_NONBLOCK" -compact
|
||||
.It Dv TFD_CLOEXEC
|
||||
The newly generated file descriptor will close-on-exec.
|
||||
.It Dv TFD_NONBLOCK
|
||||
Do not block on read/write operations.
|
||||
.El
|
||||
.It Fn timerfd_gettime
|
||||
Retrieve the current state of the timer denoted by
|
||||
.Fa fd .
|
||||
The result is stored in
|
||||
.Fa curr_value
|
||||
as a
|
||||
.Dv struct itimerspec .
|
||||
The
|
||||
.Fa it_value
|
||||
and
|
||||
.Fa it_interval
|
||||
members of
|
||||
.Fa curr_value
|
||||
represent the relative time until the next expiration and the interval
|
||||
reload value last set by
|
||||
.Fn timerfd_settime ,
|
||||
respectively.
|
||||
.It Fn timerfd_settime
|
||||
Update the timer denoted by
|
||||
.Fa fd
|
||||
with the
|
||||
.Dv struct itimerspec
|
||||
in
|
||||
.Fa new_value .
|
||||
The
|
||||
.Fa it_value
|
||||
member of
|
||||
.Fa new_value
|
||||
should contain the amount of time before the timer expires, or zero if the
|
||||
timer should be disarmed.
|
||||
The
|
||||
.Fa it_interval
|
||||
member should contain the reload time if an interval timer is desired.
|
||||
.Pp
|
||||
The previous timer state will be stored in
|
||||
.Fa old_value
|
||||
given
|
||||
.Fa old_value
|
||||
is not
|
||||
.Dv NULL .
|
||||
.Pp
|
||||
The
|
||||
.Fa flags
|
||||
argument may contain the result of
|
||||
.Em or Ns 'ing
|
||||
the following values:
|
||||
.Pp
|
||||
.Bl -tag -width TFD_TIMER_CANCEL_ON_SET -compact
|
||||
.It Dv TFD_TIMER_ABSTIME
|
||||
Expiration will occur at the absolute time provided in
|
||||
.Fa new_value .
|
||||
Normally,
|
||||
.Fa new_value
|
||||
represents a relative time compared to the timer's
|
||||
.Fa clockid
|
||||
clock.
|
||||
.It Dv TFD_TIMER_CANCEL_ON_SET
|
||||
If
|
||||
.Fa clockid
|
||||
has been set to
|
||||
.Dv CLOCK_REALTIME
|
||||
and the realtime clock has experienced a discontinuous jump,
|
||||
then the timer will be canceled and the next
|
||||
.Xr read 2
|
||||
will fail with
|
||||
.Dv ECANCELED .
|
||||
.El
|
||||
.El
|
||||
.Pp
|
||||
File operations have the following semantics:
|
||||
.Bl -tag -width ioctl
|
||||
.It Xr read 2
|
||||
Transfer the number of timer expirations that have occurred since the last
|
||||
successful
|
||||
.Xr read 2
|
||||
or
|
||||
.Fn timerfd_settime
|
||||
into the output buffer of size
|
||||
.Vt uint64_t .
|
||||
If the expiration counter is zero,
|
||||
.Xr read 2
|
||||
blocks until a timer expiration occurs unless
|
||||
.Dv TFD_NONBLOCK
|
||||
is set, where
|
||||
.Dv EAGAIN
|
||||
is returned.
|
||||
.It Xr poll 2
|
||||
The file descriptor is readable when its timer expiration counter is greater
|
||||
than zero.
|
||||
.It Xr ioctl 2
|
||||
.Bl -tag -width FIONREAD
|
||||
.It Dv FIOASYNC int
|
||||
A non-zero input will set the FASYNC flag.
|
||||
A zero input will clear the FASYNC flag.
|
||||
.It Dv FIONBIO int
|
||||
A non-zero input will set the FNONBLOCK flag.
|
||||
A zero input will clear the FNONBLOCK flag.
|
||||
.El
|
||||
.El
|
||||
.Sh RETURN VALUES
|
||||
The
|
||||
.Fn timerfd_create
|
||||
system call creates a
|
||||
.Nm
|
||||
object and returns its file descriptor.
|
||||
If an error occurs, -1 is returned and the global variable
|
||||
.Fa errno
|
||||
is set to indicate the error.
|
||||
.Pp
|
||||
The
|
||||
.Fn timerfd_gettime
|
||||
and
|
||||
.Fn timerfd_settime
|
||||
system calls return 0 on success.
|
||||
If an error occurs, -1 is returned and the global variable
|
||||
.Fa errno
|
||||
is set to indicate the error.
|
||||
.Sh ERRORS
|
||||
The
|
||||
.Fn timerfd_create
|
||||
system call fails if:
|
||||
.Bl -tag -width Er
|
||||
.It Bq Er EINVAL
|
||||
The specified
|
||||
.Fa clockid
|
||||
is not supported.
|
||||
.It Bq Er EINVAL
|
||||
The provided
|
||||
.Fa flags
|
||||
are invalid.
|
||||
.It Bq Er EMFILE
|
||||
The per-process descriptor table is full.
|
||||
.It Bq Er ENFILE
|
||||
The system file table is full.
|
||||
.It Bq Er ENOMEM
|
||||
The kernel failed to allocate enough memory for the timer.
|
||||
.El
|
||||
.Pp
|
||||
Both
|
||||
.Fn timerfd_gettime
|
||||
and
|
||||
.Fn timerfd_settime
|
||||
system calls fail if:
|
||||
.Bl -tag -width Er
|
||||
.It Bq Er EBADF
|
||||
The provided
|
||||
.Fa fd
|
||||
is invalid.
|
||||
.It Bq Er EFAULT
|
||||
The addresses provided by
|
||||
.Fa curr_value ,
|
||||
.Fa new_value ,
|
||||
or
|
||||
.Fa old_value
|
||||
are invalid.
|
||||
.It Bq Er EINVAL
|
||||
The provided
|
||||
.Fa fd
|
||||
is valid, but was not generated by
|
||||
.Fn timerfd_create .
|
||||
.El
|
||||
.Pp
|
||||
The following errors only apply to
|
||||
.Fn timerfd_settime :
|
||||
.Bl -tag -width Er
|
||||
.It Bq Er EINVAL
|
||||
The provided
|
||||
.Fa flags
|
||||
are invalid.
|
||||
.It Bq Er EINVAL
|
||||
A nanosecond field in the
|
||||
.Fa new_value
|
||||
argument specified a value less than zero, or greater than or equal to 10^9.
|
||||
.It Bq Er ECANCELED
|
||||
The timer was created with the clock ID
|
||||
.Dv CLOCK_REALTIME ,
|
||||
was configured with the
|
||||
.Dv TFD_TIMER_CANCEL_ON_SET
|
||||
flag, and the system realtime clock experienced a discontinuous change without
|
||||
being read.
|
||||
.El
|
||||
.Pp
|
||||
A read from a
|
||||
.Nm
|
||||
object fails if:
|
||||
.Bl -tag -width Er
|
||||
.It Bq Er EAGAIN
|
||||
The timer's expiration counter is zero and the
|
||||
.Nm
|
||||
object is is set for non-blocking I/O.
|
||||
.It Bq Er ECANCELED
|
||||
The timer was created with the clock ID
|
||||
.Dv CLOCK_REALTIME ,
|
||||
was configured with the
|
||||
.Dv TFD_TIMER_CANCEL_ON_SET
|
||||
flag, and the system realtime clock experienced a discontinuous change.
|
||||
.It Bq Er EINVAL
|
||||
The size of the read buffer is not large enough to hold the
|
||||
.Vt uint64_t
|
||||
sized timer expiration counter.
|
||||
.El
|
||||
.Sh SEE ALSO
|
||||
.Xr eventfd 2 ,
|
||||
.Xr kqueue 2 ,
|
||||
.Xr poll 2 ,
|
||||
.Xr read 2 ,
|
||||
.Xr timer_create 2 ,
|
||||
.Xr timer_gettime 2 ,
|
||||
.Xr timer_settime 2
|
||||
.Sh STANDARDS
|
||||
The
|
||||
.Nm
|
||||
system calls originated from Linux and are non-standard.
|
||||
.Sh HISTORY
|
||||
.An -nosplit
|
||||
The
|
||||
.Nm
|
||||
facility was originally ported to
|
||||
.Fx Ns 's
|
||||
Linux compatibility layer by
|
||||
.An Dmitry Chagin Aq Mt dchagin@FreeBSD.org
|
||||
in
|
||||
.Fx 12.0 .
|
||||
It was revised and adapted to be native by
|
||||
.An Jake Freeland Aq Mt jfree@FreeBSD.org
|
||||
in
|
||||
.Fx 14.0 .
|
Loading…
Reference in New Issue
Block a user