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| Rev | Author | Line No. | Line |
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| 2 | pj | 1 | /* |
| 2 | * Project: S.Ha.R.K. |
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| 3 | * |
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| 4 | * Coordinators: |
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| 5 | * Giorgio Buttazzo <giorgio@sssup.it> |
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| 6 | * Paolo Gai <pj@gandalf.sssup.it> |
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| 7 | * |
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| 8 | * Authors : |
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| 9 | * Paolo Gai <pj@gandalf.sssup.it> |
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| 10 | * Massimiliano Giorgi <massy@gandalf.sssup.it> |
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| 11 | * Luca Abeni <luca@gandalf.sssup.it> |
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| 12 | * (see the web pages for full authors list) |
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| 13 | * |
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| 14 | * ReTiS Lab (Scuola Superiore S.Anna - Pisa - Italy) |
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| 15 | * |
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| 16 | * http://www.sssup.it |
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| 17 | * http://retis.sssup.it |
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| 18 | * http://shark.sssup.it |
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| 19 | */ |
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| 20 | |||
| 21 | /* |
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| 22 | * Copyright (C) 2000 Massimiliano Giorgi |
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| 23 | * |
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| 24 | * This program is free software; you can redistribute it and/or modify |
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| 25 | * it under the terms of the GNU General Public License as published by |
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| 26 | * the Free Software Foundation; either version 2 of the License, or |
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| 27 | * (at your option) any later version. |
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| 28 | * |
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| 29 | * This program is distributed in the hope that it will be useful, |
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| 30 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 31 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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| 32 | * GNU General Public License for more details. |
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| 33 | * |
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| 34 | * You should have received a copy of the GNU General Public License |
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| 35 | * along with this program; if not, write to the Free Software |
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| 36 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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| 37 | * |
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| 38 | */ |
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| 39 | |||
| 40 | #include "bqueue.h" |
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| 41 | #include "glue.h" |
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| 42 | |||
| 43 | int look_init(look_queue_t *q) |
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| 44 | { |
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| 45 | __b_fastmutex_init(&q->mutex); |
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| 46 | q->disk=NULL; |
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| 47 | q->queue[0]=NULL; |
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| 48 | q->queue[1]=NULL; |
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| 49 | q->dir=0; |
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| 50 | q->counter=0; |
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| 51 | return 0; |
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| 52 | } |
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| 53 | |||
| 54 | int look_numelements(look_queue_t *q) |
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| 55 | { |
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| 56 | return q->counter; |
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| 57 | } |
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| 58 | |||
| 59 | /* 0 -> no starvation */ |
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| 60 | /* 1 -> possible starvation */ |
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| 61 | #define STARVATION 1 |
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| 62 | |||
| 63 | int look_insertrequest(look_queue_t *q, request_prologue_t *e) |
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| 64 | { |
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| 65 | request_prologue_t *p,*o; |
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| 66 | |||
| 67 | __b_fastmutex_lock(&q->mutex); |
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| 68 | |||
| 69 | if (q->queue[q->dir]==NULL) q->dir^=1; |
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| 70 | |||
| 71 | if (q->queue[q->dir]==NULL) { |
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| 72 | q->queue[q->dir]=e; |
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| 73 | e->x.next=NULL; |
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| 74 | } else { |
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| 75 | |||
| 76 | if (e->cylinder==q->queue[q->dir]->cylinder) { |
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| 77 | if (q->dir==STARVATION) goto HI_INS; |
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| 78 | else goto LO_INS; |
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| 79 | } |
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| 80 | |||
| 81 | if (e->cylinder<q->queue[q->dir]->cylinder) { |
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| 82 | LO_INS: |
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| 83 | /* insert into low queue */ |
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| 84 | o=NULL; |
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| 85 | p=q->queue[0]; |
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| 86 | while (p!=NULL) { |
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| 87 | if (e->cylinder>p->cylinder) break; |
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| 88 | o=p; |
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| 89 | p=p->x.next; |
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| 90 | } |
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| 91 | if (o==NULL) q->queue[0]=e; |
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| 92 | else o->x.next=e; |
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| 93 | e->x.next=p; |
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| 94 | } else { |
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| 95 | HI_INS: |
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| 96 | /* insert into high queue */ |
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| 97 | o=NULL; |
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| 98 | p=q->queue[1]; |
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| 99 | while (p!=NULL) { |
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| 100 | if (e->cylinder<p->cylinder) break; |
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| 101 | o=p; |
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| 102 | p=p->x.next; |
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| 103 | } |
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| 104 | if (o==NULL) q->queue[1]=e; |
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| 105 | else o->x.next=e; |
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| 106 | e->x.next=p; |
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| 107 | } |
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| 108 | |||
| 109 | } |
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| 110 | |||
| 111 | q->counter++; |
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| 112 | __b_fastmutex_unlock(&q->mutex); |
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| 113 | return 0; |
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| 114 | } |
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| 115 | |||
| 116 | request_prologue_t *look_getrequest(look_queue_t *q) |
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| 117 | { |
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| 118 | request_prologue_t *ret; |
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| 119 | __b_fastmutex_lock(&q->mutex); |
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| 120 | ret=q->queue[q->dir]; |
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| 121 | if (ret==NULL) { |
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| 122 | q->dir^=1; |
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| 123 | ret=q->queue[q->dir]; |
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| 124 | } |
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| 125 | __b_fastmutex_lock(&q->mutex); |
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| 126 | return ret; |
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| 127 | } |
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| 128 | |||
| 129 | int look_removerequest(look_queue_t *q) |
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| 130 | { |
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| 131 | __b_fastmutex_lock(&q->mutex); |
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| 132 | assertk(q->queue[q->dir]!=NULL); |
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| 133 | q->queue[q->dir]=q->queue[q->dir]->x.next; |
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| 134 | q->counter--; |
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| 135 | __b_fastmutex_unlock(&q->mutex); |
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| 136 | return 0; |
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| 137 | } |