190 lines
4.5 KiB
Groff
190 lines
4.5 KiB
Groff
.\"
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.\" Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd January 16, 2004
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.Dt G_EVENT 9
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.Os
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.Sh NAME
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.Nm g_post_event ,
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.Nm g_waitfor_event ,
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.Nm g_cancel_event
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.Nd "GEOM events management"
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.Sh SYNOPSIS
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.In geom/geom.h
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.Ft int
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.Fn g_post_event "g_event_t *func" "void *arg" "int flag" ...
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.Ft int
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.Fn g_waitfor_event "g_event_t *func" "void *arg" "int flag" ...
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.Ft void
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.Fn g_cancel_event "void *ref"
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.Sh DESCRIPTION
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The GEOM framework has its own event queue to inform classes about important
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events.
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The event queue can be also used by GEOM classes themselves, for example
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to work around some restrictions in the I/O path, where sleeping, heavy weight
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tasks, etc.\& are not permitted.
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.Pp
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The
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.Fn g_post_event
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function tells the GEOM framework to call function
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.Fa func
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with argument
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.Fa arg
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from the event queue.
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The
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.Fa flag
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argument is passed to
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.Xr malloc 9
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for memory allocations inside of
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.Fn g_post_event .
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The only allowed flags are
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.Dv M_WAITOK
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and
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.Dv M_NOWAIT .
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The rest of the arguments are used as references to identify the event.
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An event can be canceled by using any of the given references as an
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argument to
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.Fn g_cancel_event .
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The list of references has to end with a
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.Dv NULL
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value.
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.Pp
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The
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.Fn g_waitfor_event
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function is a blocking version of the
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.Fn g_post_event
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function.
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It waits until the event is finished or canceled and then returns.
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.Pp
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The
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.Fn g_cancel_event
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function cancels all event(s) identified by
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.Fa ref .
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Cancellation is equivalent to calling the requested function
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with requested arguments and argument
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.Fa flag
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set to
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.Dv EV_CANCEL .
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.Sh RESTRICTIONS/CONDITIONS
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.Fn g_post_event :
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.Bl -item -offset indent
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.It
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The argument
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.Fa flag
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has to be
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.Dv M_WAITOK
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or
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.Dv M_NOWAIT .
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.It
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The list of references has to end with a
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.Dv NULL
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value.
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.El
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.Pp
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.Fn g_waitfor_event :
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.Bl -item -offset indent
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.It
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The argument
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.Fa flag
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has to be
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.Dv M_WAITOK
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or
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.Dv M_NOWAIT .
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.It
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The list of references has to end with a
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.Dv NULL
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value.
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.It
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The
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.Fn g_waitfor_event
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function cannot be called from an event, since doing so would result
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in a deadlock.
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.El
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.Sh RETURN VALUES
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The
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.Fn g_post_event
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and
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.Fn g_waitfor_event
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functions
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return 0 if successful; otherwise an error code is returned.
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.Sh EXAMPLES
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Example of a function called from the event queue.
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.Bd -literal -offset indent
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void
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example_event(void *arg, int flag)
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{
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if (flag == EV_CANCEL) {
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printf("Event with argument %p canceled.\\n", arg);
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return;
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}
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printf("Event with argument %p called.\\n", arg);
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}
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.Ed
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.Sh ERRORS
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Possible errors for the
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.Fn g_post_event
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function:
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.Bl -tag -width Er
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.It Bq Er ENOMEM
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The
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.Fa flag
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argument was set to
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.Dv M_NOWAIT
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and there was insufficient memory.
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.El
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.Pp
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Possible errors for the
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.Fn g_waitfor_event
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function:
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.Bl -tag -width Er
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.It Bq Er EAGAIN
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The event was canceled.
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.It Bq Er ENOMEM
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The
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.Fa flag
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argument was set to
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.Dv M_NOWAIT
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and there was insufficient memory.
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.El
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.Sh SEE ALSO
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.Xr geom 4 ,
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.Xr DECLARE_GEOM_CLASS 9 ,
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.Xr g_access 9 ,
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.Xr g_attach 9 ,
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.Xr g_bio 9 ,
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.Xr g_consumer 9 ,
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.Xr g_data 9 ,
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.Xr g_geom 9 ,
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.Xr g_provider 9 ,
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.Xr g_provider_by_name 9 ,
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.Xr g_wither_geom 9
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.Sh AUTHORS
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.An -nosplit
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This manual page was written by
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.An Pawel Jakub Dawidek Aq Mt pjd@FreeBSD.org .
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