181 lines
4.3 KiB
Groff
181 lines
4.3 KiB
Groff
.\"
|
|
.\" Copyright (c) 2004 Pawel Jakub Dawidek <pjd@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, 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 DEVELOPERS ``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 DEVELOPERS 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 January 16, 2004
|
|
.Dt g_event 9
|
|
.Os
|
|
.Sh NAME
|
|
.Nm g_post_event ,
|
|
.Nm g_waitfor_event ,
|
|
.Nm g_cancel_event
|
|
.Nd "events management"
|
|
.Sh SYNOPSIS
|
|
.In geom/geom.h
|
|
.Ft int
|
|
.Fn g_post_event "g_event_t *func" "void *arg" "int flag" ...
|
|
.Ft int
|
|
.Fn g_waitfor_event "g_event_t *func" "void *arg" "int flag" ...
|
|
.Ft void
|
|
.Fn g_cancel_event "void *ref"
|
|
.Sh DESCRIPTION
|
|
The GEOM has its own event queue to inform classes about important things.
|
|
The event queue can be also used by classes, mostly for running away
|
|
from I/O path.
|
|
Sleeping, heavy weight tasks, etc. are not permitted on I/O path and
|
|
events are the cure to avoid such situations.
|
|
.Pp
|
|
The
|
|
.Fn g_post_event
|
|
function tells GEOM to call function
|
|
.Fa func
|
|
with argument
|
|
.Fa arg
|
|
from the event queue.
|
|
The
|
|
.Fa flag
|
|
argument is a flag for
|
|
.Xr malloc 9
|
|
that should be used by GEOM.
|
|
Only the flags
|
|
.Dv M_WAITOK
|
|
or
|
|
.Dv M_NOWAIT
|
|
can be used.
|
|
The rest of the arguments are used as references.
|
|
An event can be canceled by using any of given references as an
|
|
argument to the
|
|
.Fn g_cancel_event
|
|
function.
|
|
The list of references has to end with a
|
|
.Dv NULL
|
|
value.
|
|
.Pp
|
|
The
|
|
.Fn g_waitfor_event
|
|
function is a blocking version of the
|
|
.Fn g_post_event
|
|
function.
|
|
It waits until the event is finished or canceled and then returns.
|
|
.Pp
|
|
The
|
|
.Fn g_cancel_event
|
|
function cancels event(s) identified by
|
|
.Fa ref .
|
|
Cancellation is equivalent to calling the requested function
|
|
with requested arguments and argument
|
|
.Fa flag
|
|
set to
|
|
.Dv EV_CANCEL .
|
|
.Sh RESTRICTIONS/CONDITIONS
|
|
.Fn g_post_event :
|
|
.Bl -item -offset indent
|
|
.It
|
|
The argument
|
|
.Fa flag
|
|
has to be
|
|
.Dv M_WAITOK
|
|
or
|
|
.Dv M_NOWAIT .
|
|
.It
|
|
The list of references has to end with a
|
|
.Dv NULL
|
|
value.
|
|
.El
|
|
.Pp
|
|
.Fn g_waitfor_event :
|
|
.Bl -item -offset indent
|
|
.It
|
|
The argument
|
|
.Fa flag
|
|
has to be
|
|
.Dv M_WAITOK
|
|
or
|
|
.Dv M_NOWAIT .
|
|
.It
|
|
The list of references has to end with a
|
|
.Dv NULL
|
|
value.
|
|
.It
|
|
The
|
|
.Fn g_waitfor_event
|
|
function can not be called from an event, since doing so would result
|
|
in a deadlock.
|
|
.El
|
|
.Sh RETURN VALUES
|
|
.Fn g_post_event
|
|
and
|
|
.Fn g_waitfor_event
|
|
returns the value 0 if successful; otherwise an error code is returned.
|
|
.Sh ERRORS
|
|
Possible errors for
|
|
.Fn g_post_event
|
|
function:
|
|
.Bl -tag -width Er
|
|
.It Bq Er ENOMEM
|
|
There was insufficient memory.
|
|
.El
|
|
.Pp
|
|
Possible errors for
|
|
.Fn g_waitfor_event
|
|
function:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EAGAIN
|
|
The event was canceled.
|
|
.It Bq Er ENOMEM
|
|
There was insufficient memory.
|
|
.El
|
|
.Sh EXAMPLES
|
|
Example of a function called from the event queue.
|
|
.Bd -literal -offset indent
|
|
void
|
|
example_event(void *arg, int flag)
|
|
{
|
|
|
|
if (flag == EV_CANCEL) {
|
|
printf("Event with argument %p canceled.\\n", arg);
|
|
return;
|
|
}
|
|
|
|
printf("Event with argument %p called.\\n", arg);
|
|
}
|
|
.Ed
|
|
.Sh SEE ALSO
|
|
.Xr DECLARE_GEOM_CLASS 9 ,
|
|
.Xr geom 4 ,
|
|
.Xr g_access 9 ,
|
|
.Xr g_attach 9 ,
|
|
.Xr g_bio 9 ,
|
|
.Xr g_consumer 9 ,
|
|
.Xr g_data 9 ,
|
|
.Xr g_geom 9 ,
|
|
.Xr g_provider 9 ,
|
|
.Xr g_provider_by_name 9 ,
|
|
.Xr g_wither_geom 9
|
|
.Sh AUTHORS
|
|
.An -nosplit
|
|
This manual page was written by
|
|
.An Pawel Jakub Dawidek Aq pjd@FreeBSD.org .
|