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callcontext.c revision 1.7 
      1 /*	$NetBSD: callcontext.c,v 1.7 2007/06/06 01:55:00 pooka Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 2006 Antti Kantee.  All Rights Reserved.
      5  *
      6  * Redistribution and use in source and binary forms, with or without
      7  * modification, are permitted provided that the following conditions
      8  * are met:
      9  * 1. Redistributions of source code must retain the above copyright
     10  *    notice, this list of conditions and the following disclaimer.
     11  * 2. Redistributions in binary form must reproduce the above copyright
     12  *    notice, this list of conditions and the following disclaimer in the
     13  *    documentation and/or other materials provided with the distribution.
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
     16  * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     17  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     18  * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
     21  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     25  * SUCH DAMAGE.
     26  */
     27 
     28 #include <sys/cdefs.h>
     29 #if !defined(lint)
     30 __RCSID("$NetBSD: callcontext.c,v 1.7 2007/06/06 01:55:00 pooka Exp $");
     31 #endif /* !lint */
     32 
     33 #include <sys/types.h>
     34 
     35 #include <assert.h>
     36 #include <puffs.h>
     37 #include <stdio.h>
     38 #include <stdlib.h>
     39 #include <string.h>
     40 #include <ucontext.h>
     41 
     42 #include "puffs_priv.h"
     43 
     44 /*
     45  * user stuff
     46  */
     47 
     48 void
     49 puffs_cc_yield(struct puffs_cc *pcc)
     50 {
     51 
     52 	assert(pcc->pcc_flags & PCC_REALCC);
     53 	pcc->pcc_flags &= ~PCC_BORROWED;
     54 
     55 	/* romanes eunt domus */
     56 	swapcontext(&pcc->pcc_uc, &pcc->pcc_uc_ret);
     57 }
     58 
     59 void
     60 puffs_cc_continue(struct puffs_cc *pcc)
     61 {
     62 
     63 	assert(pcc->pcc_flags & PCC_REALCC);
     64 
     65 	/* ramble on */
     66 	swapcontext(&pcc->pcc_uc_ret, &pcc->pcc_uc);
     67 }
     68 
     69 /*
     70  * "Borrows" pcc, *NOT* called from pcc owner.  Acts like continue.
     71  * So the idea is to use this, give something the context back to
     72  * run to completion and then jump back to where ever this was called
     73  * from after the op dispatching is complete (or if the pcc decides to
     74  * yield again).
     75  */
     76 void
     77 puffs_goto(struct puffs_cc *loanpcc)
     78 {
     79 
     80 	assert(loanpcc->pcc_flags & PCC_REALCC);
     81 	loanpcc->pcc_flags |= PCC_BORROWED;
     82 
     83 	swapcontext(&loanpcc->pcc_uc_ret, &loanpcc->pcc_uc);
     84 }
     85 
     86 struct puffs_usermount *
     87 puffs_cc_getusermount(struct puffs_cc *pcc)
     88 {
     89 
     90 	return pcc->pcc_pu;
     91 }
     92 
     93 void *
     94 puffs_cc_getspecific(struct puffs_cc *pcc)
     95 {
     96 
     97 	return puffs_getspecific(pcc->pcc_pu);
     98 }
     99 
    100 struct puffs_cc *
    101 puffs_cc_create(struct puffs_usermount *pu)
    102 {
    103 	struct puffs_cc *volatile pcc;
    104 	stack_t *st;
    105 
    106 	pcc = malloc(sizeof(struct puffs_cc));
    107 	if (!pcc)
    108 		return NULL;
    109 	memset(pcc, 0, sizeof(struct puffs_cc));
    110 	pcc->pcc_pu = pu;
    111 	pcc->pcc_flags = PCC_REALCC;
    112 
    113 	/* initialize both ucontext's */
    114 	if (getcontext(&pcc->pcc_uc) == -1) {
    115 		free(pcc);
    116 		return NULL;
    117 	}
    118 	if (getcontext(&pcc->pcc_uc_ret) == -1) {
    119 		free(pcc);
    120 		return NULL;
    121 	}
    122 	/* return here.  it won't actually be "here" due to swapcontext() */
    123 	pcc->pcc_uc.uc_link = &pcc->pcc_uc_ret;
    124 
    125 	/* allocate stack for execution */
    126 	st = &pcc->pcc_uc.uc_stack;
    127 	st->ss_sp = pcc->pcc_stack = malloc(pu->pu_cc_stacksize);
    128 	if (st->ss_sp == NULL) {
    129 		free(pcc);
    130 		return NULL;
    131 	}
    132 	st->ss_size = pu->pu_cc_stacksize;
    133 	st->ss_flags = 0;
    134 
    135 	/*
    136 	 * Give us an initial context to jump to.
    137 	 *
    138 	 * XXX: Our manual page says that portable code shouldn't rely on
    139 	 * being able to pass pointers through makecontext().  kjk says
    140 	 * that NetBSD code doesn't need to worry about this.  uwe says
    141 	 * it would be like putting a "keep away from children" sign on a
    142 	 * box of toys.  I didn't ask what simon says; he's probably busy
    143 	 * "fixing" typos in comments.
    144 	 */
    145 	makecontext(&pcc->pcc_uc, (void *)puffs_calldispatcher,
    146 	    1, (uintptr_t)pcc);
    147 
    148 	return pcc;
    149 }
    150 
    151 void
    152 puffs_cc_destroy(struct puffs_cc *pcc)
    153 {
    154 
    155 	if (pcc->pcc_preq)
    156 		free(pcc->pcc_preq);
    157 	free(pcc->pcc_stack);
    158 	free(pcc);
    159 }
    160