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/*
Copyright (C) 1993, 1994 Free Software Foundation
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2, or (at
your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
#include "ioserver.h"
/* The conch must be locked when calling this routine. */
/* Remove any current holder of conch C. */
error_t
ioserver_get_conch (struct conch *c)
{
struct shared_io *user_sh;
int error = 0;
again:
user_sh = c->holder_shared_page;
if (user_sh)
{
spin_lock (&user_sh->lock);
switch (user_sh->conch_status)
{
case USER_HAS_CONCH:
user_sh->conch_status = USER_RELEASE_CONCH;
/* fall through ... */
case USER_RELEASE_CONCH:
spin_unlock (&user_sh->lock);
condition_wait (&c->wait, c->lock);
/* Anything can have happened */
goto again;
case USER_COULD_HAVE_CONCH:
user_sh->conch_status = USER_HAS_NOT_CONCH;
spin_unlock (&user_sh->lock);
error = ioserver_fetch_shared_data (c->holder);
break;
case USER_HAS_NOT_CONCH:
spin_unlock (&user_sh->lock);
break;
}
}
c->holder = 0;
c->holder_shared_page = 0;
return error;
}
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