f827ccb9a3
Documented function and macros are: - DECLARE_GEOM_CLASS(), - g_attach(), - g_detach(), - g_new_bio(), - g_clone_bio(), - g_destroy_bio(), - g_new_consumer(), - g_destroy_consumer(), - g_read_data(), - g_write_data(), - g_post_event(), - g_waitfor_event(), - g_cancel_event(), - g_new_geomf(), - g_destroy_geom(), - g_new_providerf(), - g_destroy_provider(), - g_error_provider(), - g_provider_by_name(), - g_wither_geom(). and more to come. I want to thanks following people for help with those documents: Slawek Zak <zaks@prioris.mini.pw.edu.pl> Simon L. Nielsen <simon@FreeBSD.org> Pieter de Boer <g.p.de.boer@st.hanze.nl> and of course Poul-Henning Kamp <phk@FreeBSD.org> Reviewed by: phk, scottl Approved by: phk, scottl (mentor)
180 lines
4.3 KiB
Groff
180 lines
4.3 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 "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 has its own event queue to inform classes about important things.
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The event queue can be also used by classes, mostly for running away
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from I/O path.
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Sleeping, heavy weight tasks, etc. are not permitted on I/O path and
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events are the cure to avoid such situations.
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.Pp
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The
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.Fn g_post_event
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function tells GEOM 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 a flag for
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.Xr malloc 9
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that should be used by GEOM.
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Only the flags
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.Dv M_WAITOK
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or
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.Dv M_NOWAIT
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can be used.
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The rest of the arguments are used as references.
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An event can be canceled by using any of given references as an
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argument to the
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.Fn g_cancel_event
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function.
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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 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 can not 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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.Fn g_post_event
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and
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.Fn g_waitfor_event
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returns the value 0 if successful; otherwise an error code is returned.
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.Sh ERRORS
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Possible errors for
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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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There was insufficient memory.
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.El
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.Pp
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Possible errors for
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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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There was insufficient memory.
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.El
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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 SEE ALSO
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.Xr DECLARE_GEOM_CLASS 9 ,
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.Xr geom 4 ,
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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 pjd@FreeBSD.org .
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