{"id":1415,"date":"2012-03-10T21:40:59","date_gmt":"2012-03-10T03:40:59","guid":{"rendered":"http:\/\/peta.okechan.net\/blog\/?p=1415"},"modified":"2012-03-14T11:21:44","modified_gmt":"2012-03-14T02:21:44","slug":"xv6%e3%82%bd%e3%83%bc%e3%82%b9%e3%82%b3%e3%83%bc%e3%83%89%e3%83%aa%e3%83%bc%e3%83%87%e3%82%a3%e3%83%b3%e3%82%b0-%e3%81%9d%e3%81%ae35","status":"publish","type":"post","link":"https:\/\/peta.okechan.net\/blog\/archives\/1415","title":{"rendered":"[xv6 #34] Chapter 3 – Locking – Race conditions"},"content":{"rendered":"

\u30c6\u30ad\u30b9\u30c8\u306e43\u301c45\u30da\u30fc\u30b8<\/p>\n

\u672c\u6587<\/h3>\n

\u306a\u305c\u30ed\u30c3\u30af\u304c\u5fc5\u8981\u304b\u3001\u305d\u306e\u4f8b\u3068\u3057\u3066\u3001xv6\u306b\u304a\u3051\u308bIDE\u306e\u30c7\u30a3\u30b9\u30af\u306e\u3088\u3046\u306b\u3001\u3044\u304f\u3064\u304b\u306e\u30d7\u30ed\u30bb\u30c3\u30b5\u304c\u4e00\u3064\u306e\u30c7\u30a3\u30b9\u30af\u3092\u5171\u6709\u3059\u308b\u5834\u5408\u3092\u8003\u3048\u308b\u3002
\n\u30c7\u30a3\u30b9\u30af\u30c9\u30e9\u30a4\u30d0\u306f\u3001\u672a\u5b9f\u884c\u306e\u30c7\u30a3\u30b9\u30af\u3078\u306e\u30ea\u30af\u30a8\u30b9\u30c8\u306e\u30ea\u30f3\u30af\u30ea\u30b9\u30c8\u3092\u7ba1\u7406\uff08ide.c\u306eidequeue\u306f\u73fe\u5728\u8aad\u307f\u66f8\u304d\u4e2d\u306e\u30d0\u30c3\u30d5\u30a1\u3092\u6307\u3057\u3001idequeue->qnext\u306f\u6b21\u306b\u51e6\u7406\u3055\u308c\u308b\u3079\u304d\u30d0\u30c3\u30d5\u30a1\u3092\u6307\u3059\u3002\uff09\u3057\u3001\u30d7\u30ed\u30bb\u30c3\u30b5\u306f\u3001\u540c\u6642\u306b\u305d\u306e\u30ea\u30b9\u30c8\u3078\u65b0\u3057\u3044\u30ea\u30af\u30a8\u30b9\u30c8\u3092\u8ffd\u52a0\u3059\u308b\u3060\u308d\u3046\uff08ide.c\u306eiderw\u95a2\u6570\u3092\u53c2\u7167\uff09\u3002
\n\u3082\u3057\u3001\u30ea\u30af\u30a8\u30b9\u30c8\u306e\u540c\u6642\u767a\u751f\u304c\u3042\u308a\u3048\u306a\u3044\u306e\u306a\u3089\u3070\u3001\u305d\u306e\u30ea\u30f3\u30af\u30ea\u30b9\u30c8\u306f\u4ee5\u4e0b\u306e\u3088\u3046\u306b\u5b9f\u88c5\u51fa\u6765\u308b\u3002<\/p>\n

struct list {\n  int data;\n  struct list *next;\n};\n\nstruct list *list = 0;\n\nvoid\ninsert(int data)\n{\n  struct list *l;\n\n  l = malloc(sizeof *l);\n  l->data = data;\n  l->next = list;\n  list = l;\n}<\/pre>\n
\u3053\u306e\u5b9f\u88c5\u306e\u6b63\u3057\u3055\u3092\u8abf\u3079\u308b\u4e8b\u306f\u3001\u30c7\u30fc\u30bf\u69cb\u9020\u3068\u30a2\u30eb\u30b4\u30ea\u30ba\u30e0\u306e\u6388\u696d\u306b\u304a\u3051\u308b\u5178\u578b\u7684\u306a\u8ab2\u984c\u3067\u3042\u308b\u3002
\n\u3053\u306e\u5b9f\u88c5\u306f\u3001\u6b63\u3057\u3044\u3068\u8a3c\u660e\u3067\u304d\u308b\u304c\u3001\u5c11\u306a\u304f\u3068\u3082\u30de\u30eb\u30c1\u30d7\u30ed\u30bb\u30c3\u30b5\u4e0a\u3067\u306f\u305d\u3046\u3067\u306f\u306a\u3044\u3002
\n2\u3064\u306e\u5225\u306eCPU\u304c\u3001\u540c\u6642\u306binsert\u95a2\u6570\u3092\u5b9f\u884c\u3057\u305f\u5834\u5408\u3001\u3069\u3061\u3089\u304b\u304c16\u884c\u76ee\u3092\u5b9f\u884c\u3059\u308b\u524d\u306b\u3001\u3069\u3061\u3089\u308215\u884c\u76ee\u3092\u5b9f\u884c\u3059\u308b\u3068\u3044\u3046\u4e8b\u614b\u304c\u8d77\u304d\u308b\u53ef\u80fd\u6027\u304c\u3042\u308b\u3002\uff08\u56f33-1\u53c2\u7167\uff09
\n\u3053\u306e\u4e8b\u614b\u304c\u767a\u751f\u3057\u305f\u5834\u5408\u3001\u30ea\u30b9\u30c8\u306e2\u3064\u306e\u30ce\u30fc\u30c9\u306enext\u306b\u306f\u3001list\u306e\u53e4\u3044\u5024\u304c\u30bb\u30c3\u30c8\u3055\u308c\u308b\u3060\u308d\u3046\u3002
\n16\u884c\u76ee\u3067list\u3078\u306e2\u3064\u306e\u4ee3\u5165\u304c\u767a\u751f\u3057\u305f\u3068\u304d\u30012\u3064\u76ee\u306e\u4ee3\u5165\u304c1\u3064\u76ee\u306e\u4ee3\u5165\u3092\u4e0a\u66f8\u304d\u3059\u308b\u3002
\n\u305d\u306e\u30ce\u30fc\u30c9\u3078\u6700\u521d\u306b\u5272\u308a\u5f53\u3066\u3089\u308c\u305f\u5024\u306f\u5931\u308f\u308c\u308b\u3060\u308d\u3046\u3002
\n\u3053\u306e\u7a2e\u306e\u554f\u984c\u306f\u3001\u7af6\u5408\u72b6\u614b\uff08\u30ec\u30fc\u30b9\u30b3\u30f3\u30c7\u30a3\u30b7\u30e7\u30f3, race condition\uff09\u3068\u547c\u3070\u308c\u308b\u3002
\n\u51e6\u7406\u904e\u7a0b\u306b\u304a\u3051\u308b\u305d\u306e\u554f\u984c\u306f\u3001\u305d\u308c\u306b\u95a2\u308f\u308b2\u3064\u306eCPU\u306e\u53b3\u5bc6\u306a\u30bf\u30a4\u30df\u30f3\u30b0\u306b\u4f9d\u5b58\u3057\u3001\u305d\u308c\u3089\u306e\u30e1\u30e2\u30ea\u64cd\u4f5c\u306f\u3001\u30e1\u30e2\u30ea\u30b7\u30b9\u30c6\u30e0\u306b\u3088\u3063\u3066\u5b9f\u884c\u3055\u308c\u3001\u305d\u306e\u7d50\u679c\u3068\u3057\u3066\u5fa9\u5143\u3059\u308b\u306e\u304c\u96e3\u3057\u304f\u306a\u308b\u3002
\n\u4f8b\u3048\u3070\u3001insert\u95a2\u6570\u3092\u30c7\u30d0\u30c3\u30b0\u3059\u308b\u3068\u304dprint\u6587\u3092\u8ffd\u52a0\u3059\u308b\u4e8b\u306f\u3001\u3053\u306e\u51e6\u7406\u904e\u7a0b\u3092\u518d\u73fe\u3067\u304d\u306a\u304f\u3059\u308b\u306e\u306b\u5341\u5206\u306a\u307b\u3069\u3001\u305d\u306e\u5b9f\u884c\u306e\u30bf\u30a4\u30df\u30f3\u30b0\u3092\u5909\u3048\u3066\u3057\u307e\u3046\u3060\u308d\u3046\u3002<\/p>\n
\u56f33-1 \u51e6\u7406\u904e\u7a0b\u306e\u4f8b
\n\"\"<\/a><\/p>\n
ide.c\u306eiderw\u95a2\u6570<\/p>\n
\/\/ Sync buf with disk. \n\/\/ If B_DIRTY is set, write buf to disk, clear B_DIRTY, set B_VALID.\n\/\/ Else if B_VALID is not set, read buf from disk, set B_VALID.\nvoid\niderw(struct buf *b)\n{\n  struct buf **pp;\n\n  if(!(b->flags & B_BUSY))\n    panic("iderw: buf not busy");\n  if((b->flags & (B_VALID|B_DIRTY)) == B_VALID)\n    panic("iderw: nothing to do");\n  if(b->dev != 0 && !havedisk1)\n    panic("iderw: ide disk 1 not present");\n\n  acquire(&idelock);  \/\/ DOC:acquire-lock\n\n  \/\/ Append b to idequeue.\n  b->qnext = 0;\n  for(pp=&idequeue; *pp; pp=&(*pp)->qnext)  \/\/ DOC:insert-queue\n    ;\n  *pp = b;\n  \n  \/\/ Start disk if necessary.\n  if(idequeue == b)\n    idestart(b);\n  \n  \/\/ Wait for request to finish.\n  \/\/ Assuming will not sleep too long: ignore proc->killed.\n  while((b->flags & (B_VALID|B_DIRTY)) != B_VALID){\n    sleep(b, &idelock);\n  }\n\n  release(&idelock);\n}<\/pre>\n
\u3053\u306e\u51e6\u7406\u904e\u7a0b\u3092\u907f\u3051\u308b\u5178\u578b\u7684\u306a\u65b9\u6cd5\u306f\u3001\u30ed\u30c3\u30af\u3092\u4f7f\u3046\u3053\u3068\u3067\u3042\u308b\u3002
\n\u30ed\u30c3\u30af\u306f\u6392\u4ed6\u3092\u78ba\u5b9f\u306b\u3059\u308b\u3002
\n\u305d\u3046\u3059\u308b\u3053\u3068\u3067\u3001\u4e00\u5ea6\u306b\u3072\u3068\u3064\u306eCPU\u3060\u3051\u304cinsert\u95a2\u6570\u3092\u5b9f\u884c\u51fa\u6765\u308b\u3002
\n\u305d\u3046\u306a\u308b\u3068\u4e0a\u3067\u8aac\u660e\u3057\u305f\u3088\u3046\u306a\u7af6\u5408\u72b6\u614b\u306f\u8d77\u304d\u306a\u304f\u306a\u308b\u3002
\n\u4e0a\u306e\u30b3\u30fc\u30c9\u306e\u30ed\u30c3\u30af\u3092\u4f7f\u3063\u305f\u6b63\u3057\u3044\u30d0\u30fc\u30b8\u30e7\u30f3\u306f\u3001\u3044\u304f\u3064\u304b\u306e\u884c\u3092\u8ffd\u52a0\u3057\u305f\u3060\u3051\u3067\u3042\u308b\u3002
\n\uff08\u8ffd\u52a0\u3068\u3044\u3046\u30b3\u30e1\u30f3\u30c8\u304c\u4ed8\u3044\u3066\u308b\u884c\u304c\u8ffd\u52a0\u3057\u305f\u884c\u3067\u3059\u3002\uff09<\/p>\n
struct list {\n  int data;\n  struct list *next;\n};\n\nstruct list *list = 0;\nstruct lock listlock; \/\/ \u8ffd\u52a0\n\nvoid\ninsert(int data)\n{\n  struct list *l;\n  \n  acquire(&listlock); \/\/ \u8ffd\u52a0\n  l = malloc(sizeof *l);\n  l->data = data;\n  l->next = list;\n  list = l;\n  release(&listlock); \/\/ \u8ffd\u52a0\n}<\/pre>\n
\u6211\u3005\u304c\u3001\u300c\u30ed\u30c3\u30af\u304c\u30c7\u30fc\u30bf\u3092\u4fdd\u8b77\u3057\u3066\u3044\u308b\u300d\u3068\u3044\u3046\u8a00\u3046\u3068\u304d\u3001\u6b63\u78ba\u306b\u306f\u300c\u30ed\u30c3\u30af\u304c\u3001\u30c7\u30fc\u30bf\u3078\u9069\u7528\u3059\u308b\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u306e\u3044\u304f\u3064\u304b\u306e\u96c6\u5408\u3092\u4fdd\u8b77\u3057\u3066\u3044\u308b\u300d\u3068\u3044\u3046\u4e8b\u3092\u610f\u5473\u3059\u308b\u3002
\n\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u3068\u306f\u3001\u4e00\u9023\u306e\u64cd\u4f5c\u3092\u901a\u3057\u3066\u7ba1\u7406\u3055\u308c\u3066\u3044\u308b\u30c7\u30fc\u30bf\u69cb\u9020\u306e\u5c5e\u6027\u3067\u3042\u308b\u3002
\n\u5178\u578b\u7684\u306b\u3001\u3072\u3068\u3064\u306e\u64cd\u4f5c\u306f\u3001\u64cd\u4f5c\u304c\u958b\u59cb\u3055\u308c\u305f\u3068\u304d\u306b\u771f\u3068\u306a\u308b\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u306b\u4f9d\u5b58\u3059\u308b\u3075\u308b\u307e\u3044\u3092\u6b63\u3059\u3002
\n\u64cd\u4f5c\u306f\u3001\u4e00\u6642\u7684\u306b\u305d\u306e\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u306b\u9055\u53cd\u3059\u308b\u304c\u3001\u7d42\u4e86\u3059\u308b\u307e\u3048\u306b\u305d\u308c\u3089\u3092\u56de\u5fa9\u3057\u306a\u3051\u308c\u3070\u306a\u3089\u306a\u3044\u3002
\n\u4f8b\u3048\u3070\u30ea\u30f3\u30af\u30ea\u30b9\u30c8\u306e\u5834\u5408\u3001\u305d\u306e\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u306f\u3001\u30ea\u30b9\u30c8\u5185\u306e\u6700\u521d\u306e\u30ce\u30fc\u30c9\u3092\u6307\u3059list\u3068\u3001\u6b21\u306e\u30ce\u30fc\u30c9\u3092\u6307\u3059\u5404\u30ce\u30fc\u30c9\u306enext\u30d5\u30a3\u30fc\u30eb\u30c9\u3067\u3042\u308b\u3002
\ninsert\u306e\u5b9f\u88c5\u306f\u3001\u4e00\u6642\u7684\u306b\u3053\u306e\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u3092\u4fb5\u5bb3\u3059\u308b\u3002
\nmalloc\u306e\u884c\u306f\u3001\u30ea\u30b9\u30c8\u306e\u65b0\u3057\u3044\u8981\u7d20\u3067\u3042\u308bl\u3092\u3001\u30ea\u30b9\u30c8\u306e\u6700\u521d\u306e\u30ce\u30fc\u30c9\u306b\u306a\u308b\u3088\u3046\u751f\u6210\u3059\u308b\u3002
\n\u3057\u304b\u3057\u3053\u306e\u6642\u70b9\u3067\u306f\u3001l\u306e\u6b21\u3078\u306e\u30dd\u30a4\u30f3\u30bf\u306f\u307e\u3060\u6b21\u306e\u30ce\u30fc\u30c9\u3092\u5dee\u3057\u3066\u306f\u304a\u3089\u305a\uff08\u305d\u308c\u306fl->next = list;\u306e\u884c\u3067\u884c\u308f\u308c\u308b\uff09\u3001list\u306f\u307e\u3060l\u3092\u5dee\u3057\u3066\u306f\u3044\u306a\u3044\uff08\u305d\u308c\u306flist = l;\u306e\u884c\u3067\u884c\u308f\u308c\u308b\uff09\u3002
\n\u6211\u3005\u304c\u4e0a\u8a18\u3067\u8abf\u67fb\u3057\u305f\u7af6\u5408\u72b6\u614b\u306f\u3001\u4e00\u6642\u7684\u306b\u4fb5\u5bb3\u3055\u308c\u3066\u3044\u308b\u9593\u3001\u305d\u306e\u30ea\u30b9\u30c8\u306e\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u306b\u4f9d\u5b58\u3057\u305f\u30b3\u30fc\u30c9\u30922\u756a\u76ee\u306eCPU\u304c\u5b9f\u884c\u3059\u308b\u3053\u3068\u306b\u3088\u3063\u3066\u3001\u767a\u751f\u3057\u305f\u3002
\n\u30ed\u30c3\u30af\u3092\u6b63\u3057\u304f\u4f7f\u3048\u3070\u3001\u4e00\u5ea6\u306b\u3072\u3068\u3064\u306eCPU\u3060\u3051\u304c\u30c7\u30fc\u30bf\u69cb\u9020\u4e0a\u3067\u64cd\u4f5c\u3059\u308b\u3053\u3068\u3092\u78ba\u5b9f\u306b\u3067\u304d\u3001\u305d\u306e\u7d50\u679c\u3001\u30c7\u30fc\u30bf\u69cb\u9020\u306e\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u304c\u4e2d\u9014\u534a\u7aef\u306a\u72b6\u614b\u306e\u3068\u304d\u306b\u3001\u4ed6\u306eCPU\u304c\u305d\u306e\u30c7\u30fc\u30bf\u69cb\u9020\u3092\u64cd\u4f5c\u3059\u308b\u3053\u3068\u306f\u306a\u304f\u306a\u308b\u3060\u308d\u3046\u3002<\/p>\n
\u611f\u60f3<\/h3>\n
\u30ed\u30c3\u30af\u306e\u4f7f\u3044\u65b9\u3092\u8efd\u304f\u3068\u3044\u3063\u305f\u3068\u3053\u308d\u3067\u3057\u3087\u3046\u304b\u3002
\n\u30b5\u30f3\u30d7\u30eb\u306e\u30b3\u30fc\u30c9\u81ea\u4f53\u306f\u3001\u30e6\u30fc\u30b6\u7a7a\u9593\u306e\u30d7\u30ed\u30b0\u30e9\u30e0\u3067\u30ed\u30c3\u30af\u3092\u4f7f\u3046\u3068\u304d\u306e\u30b3\u30fc\u30c9\u3068\u5168\u304f\u540c\u3058\u3067\u3059\u306d\u3002<\/p>\n
\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u306f\u8a33\u304c\u96e3\u3057\u3044\u306e\u3067\u305d\u306e\u307e\u307e\u3067\u3059\u304c\u3001\u3053\u3053\u3067\u3044\u3046\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u306f\u30c7\u30fc\u30bf\u69cb\u9020\u3068\u304b\u5f62\u5f0f\u3068\u304b\u4e00\u8cab\u6027\u3068\u304b\u305d\u3046\u3044\u3063\u305f\u611f\u3058\u306e\u610f\u5473\u304b\u3068\u601d\u3044\u307e\u3059\u3002<\/p>\n
\u4eca\u56de\u3001\u7279\u306b\u6700\u5f8c\u306e\u6bb5\u843d\u304c\u96e3\u3057\u3044\u3067\u3059\u3002
\n\u3053\u306e\u30c6\u30ad\u30b9\u30c8\u3084\u3063\u3066\u308b\u3068\u3001\u62bd\u8c61\u7684\u3067\u8a00\u3044\u56de\u3057\u3082\u5fae\u5999\u3067typo\u304c\u3042\u3063\u3066\u3068\u3066\u3082\u5206\u304b\u308a\u3065\u3089\u3044\u7bc0\u3084\u6bb5\u843d\u306b\u305f\u307e\u306b\u51fa\u304f\u308f\u3057\u307e\u3059\u3002
\n\u62c5\u5f53\u8005\u306e\u9055\u3044\u3067\u3057\u3087\u3046\u304b\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u30c6\u30ad\u30b9\u30c8\u306e43\u301c45\u30da\u30fc\u30b8<\/p>\n
\u672c\u6587<\/h3>\n
\u306a\u305c\u30ed\u30c3\u30af\u304c\u5fc5\u8981\u304b\u3001\u305d\u306e\u4f8b\u3068\u3057\u3066\u3001xv6\u306b\u304a\u3051\u308bIDE\u306e\u30c7\u30a3\u30b9\u30af\u306e\u3088\u3046\u306b\u3001\u3044\u304f\u3064\u304b\u306e\u30d7\u30ed\u30bb\u30c3\u30b5\u304c\u4e00\u3064\u306e\u30c7\u30a3\u30b9\u30af\u3092\u5171\u6709\u3059\u308b\u5834\u5408\u3092\u8003\u3048\u308b\u3002
\n\u30c7\u30a3\u30b9\u30af\u30c9\u30e9\u30a4\u30d0\u306f\u3001\u672a\u5b9f\u884c\u306e\u30c7\u30a3\u30b9\u30af\u3078\u306e\u30ea\u30af\u30a8\u30b9\u30c8\u306e\u30ea\u30f3\u30af\u30ea\u30b9\u30c8\u3092\u7ba1\u7406\uff08ide.c\u306eidequeue\u306f\u73fe\u5728\u8aad\u307f\u66f8\u304d\u4e2d\u306e\u30d0\u30c3\u30d5\u30a1\u3092\u6307\u3057\u3001idequeue->qnext\u306f\u6b21\u306b\u51e6\u7406\u3055\u308c\u308b\u3079\u304d\u30d0\u30c3\u30d5\u30a1\u3092\u6307\u3059\u3002\uff09\u3057\u3001\u30d7\u30ed\u30bb\u30c3\u30b5\u306f\u3001\u540c\u6642\u306b\u305d\u306e\u30ea\u30b9\u30c8\u3078\u65b0\u3057\u3044\u30ea\u30af\u30a8\u30b9\u30c8\u3092\u8ffd\u52a0\u3059\u308b\u3060\u308d\u3046\uff08ide.c\u306eiderw\u95a2\u6570\u3092\u53c2\u7167\uff09\u3002
\n\u3082\u3057\u3001\u30ea\u30af\u30a8\u30b9\u30c8\u306e\u540c\u6642\u767a\u751f\u304c\u3042\u308a\u3048\u306a\u3044\u306e\u306a\u3089\u3070\u3001\u305d\u306e\u30ea\u30f3\u30af\u30ea\u30b9\u30c8\u306f\u4ee5\u4e0b\u306e\u3088\u3046\u306b\u5b9f\u88c5\u51fa\u6765\u308b\u3002<\/p>\n
struct list {\n  int data;\n  struct list *next;\n};\n\nstruct list *list = 0;\n\nvoid\ninsert(int data)\n{\n  struct list *l;\n\n  l = malloc(sizeof *l);\n  l->data = data;\n  l->next = list;\n  list = l;\n}<\/pre>\n
\u3053\u306e\u5b9f\u88c5\u306e\u6b63\u3057\u3055\u3092\u8abf\u3079\u308b\u4e8b\u306f\u3001\u30c7\u30fc\u30bf\u69cb\u9020\u3068\u30a2\u30eb\u30b4\u30ea\u30ba\u30e0\u306e\u6388\u696d\u306b\u304a\u3051\u308b\u5178\u578b\u7684\u306a\u8ab2\u984c\u3067\u3042\u308b\u3002
\n\u3053\u306e\u5b9f\u88c5\u306f\u3001\u6b63\u3057\u3044\u3068\u8a3c\u660e\u3067\u304d\u308b\u304c\u3001\u5c11\u306a\u304f\u3068\u3082\u30de\u30eb\u30c1\u30d7\u30ed\u30bb\u30c3\u30b5\u4e0a\u3067\u306f\u305d\u3046\u3067\u306f\u306a\u3044\u3002
\n2\u3064\u306e\u5225\u306eCPU\u304c\u3001\u540c\u6642\u306binsert\u95a2\u6570\u3092\u5b9f\u884c\u3057\u305f\u5834\u5408\u3001\u3069\u3061\u3089\u304b\u304c16\u884c\u76ee\u3092\u5b9f\u884c\u3059\u308b\u524d\u306b\u3001\u3069\u3061\u3089\u308215\u884c\u76ee\u3092\u5b9f\u884c\u3059\u308b\u3068\u3044\u3046\u4e8b\u614b\u304c\u8d77\u304d\u308b\u53ef\u80fd\u6027\u304c\u3042\u308b\u3002\uff08\u56f33-1\u53c2\u7167\uff09
\n\u3053\u306e\u4e8b\u614b\u304c\u767a\u751f\u3057\u305f\u5834\u5408\u3001\u30ea\u30b9\u30c8\u306e2\u3064\u306e\u30ce\u30fc\u30c9\u306enext\u306b\u306f\u3001list\u306e\u53e4\u3044\u5024\u304c\u30bb\u30c3\u30c8\u3055\u308c\u308b\u3060\u308d\u3046\u3002
\n16\u884c\u76ee\u3067list\u3078\u306e2\u3064\u306e\u4ee3\u5165\u304c\u767a\u751f\u3057\u305f\u3068\u304d\u30012\u3064\u76ee\u306e\u4ee3\u5165\u304c1\u3064\u76ee\u306e\u4ee3\u5165\u3092\u4e0a\u66f8\u304d\u3059\u308b\u3002
\n\u305d\u306e\u30ce\u30fc\u30c9\u3078\u6700\u521d\u306b\u5272\u308a\u5f53\u3066\u3089\u308c\u305f\u5024\u306f\u5931\u308f\u308c\u308b\u3060\u308d\u3046\u3002
\n\u3053\u306e\u7a2e\u306e\u554f\u984c\u306f\u3001\u7af6\u5408\u72b6\u614b\uff08\u30ec\u30fc\u30b9\u30b3\u30f3\u30c7\u30a3\u30b7\u30e7\u30f3, race condition\uff09\u3068\u547c\u3070\u308c\u308b\u3002
\n\u51e6\u7406\u904e\u7a0b\u306b\u304a\u3051\u308b\u305d\u306e\u554f\u984c\u306f\u3001\u305d\u308c\u306b\u95a2\u308f\u308b2\u3064\u306eCPU\u306e\u53b3\u5bc6\u306a\u30bf\u30a4\u30df\u30f3\u30b0\u306b\u4f9d\u5b58\u3057\u3001\u305d\u308c\u3089\u306e\u30e1\u30e2\u30ea\u64cd\u4f5c\u306f\u3001\u30e1\u30e2\u30ea\u30b7\u30b9\u30c6\u30e0\u306b\u3088\u3063\u3066\u5b9f\u884c\u3055\u308c\u3001\u305d\u306e\u7d50\u679c\u3068\u3057\u3066\u5fa9\u5143\u3059\u308b\u306e\u304c\u96e3\u3057\u304f\u306a\u308b\u3002
\n\u4f8b\u3048\u3070\u3001insert\u95a2\u6570\u3092\u30c7\u30d0\u30c3\u30b0\u3059\u308b\u3068\u304dprint\u6587\u3092\u8ffd\u52a0\u3059\u308b\u4e8b\u306f\u3001\u3053\u306e\u51e6\u7406\u904e\u7a0b\u3092\u518d\u73fe\u3067\u304d\u306a\u304f\u3059\u308b\u306e\u306b\u5341\u5206\u306a\u307b\u3069\u3001\u305d\u306e\u5b9f\u884c\u306e\u30bf\u30a4\u30df\u30f3\u30b0\u3092\u5909\u3048\u3066\u3057\u307e\u3046\u3060\u308d\u3046\u3002<\/p>\n
\u56f33-1 \u51e6\u7406\u904e\u7a0b\u306e\u4f8b
\n\"\"<\/a><\/p>\n
ide.c\u306eiderw\u95a2\u6570<\/p>\n
\/\/ Sync buf with disk. \n\/\/ If B_DIRTY is set, write buf to disk, clear B_DIRTY, set B_VALID.\n\/\/ Else if B_VALID is not set, read buf from disk, set B_VALID.\nvoid\niderw(struct buf *b)\n{\n  struct buf **pp;\n\n  if(!(b->flags & B_BUSY))\n    panic("iderw: buf not busy");\n  if((b->flags & (B_VALID|B_DIRTY)) == B_VALID)\n    panic("iderw: nothing to do");\n  if(b->dev != 0 && !havedisk1)\n    panic("iderw: ide disk 1 not present");\n\n  acquire(&idelock);  \/\/ DOC:acquire-lock\n\n  \/\/ Append b to idequeue.\n  b->qnext = 0;\n  for(pp=&idequeue; *pp; pp=&(*pp)->qnext)  \/\/ DOC:insert-queue\n    ;\n  *pp = b;\n  \n  \/\/ Start disk if necessary.\n  if(idequeue == b)\n    idestart(b);\n  \n  \/\/ Wait for request to finish.\n  \/\/ Assuming will not sleep too long: ignore proc->killed.\n  while((b->flags & (B_VALID|B_DIRTY)) != B_VALID){\n    sleep(b, &idelock);\n  }\n\n  release(&idelock);\n}<\/pre>\n
\u3053\u306e\u51e6\u7406\u904e\u7a0b\u3092\u907f\u3051\u308b\u5178\u578b\u7684\u306a\u65b9\u6cd5\u306f\u3001\u30ed\u30c3\u30af\u3092\u4f7f\u3046\u3053\u3068\u3067\u3042\u308b\u3002
\n\u30ed\u30c3\u30af\u306f\u6392\u4ed6\u3092\u78ba\u5b9f\u306b\u3059\u308b\u3002
\n\u305d\u3046\u3059\u308b\u3053\u3068\u3067\u3001\u4e00\u5ea6\u306b\u3072\u3068\u3064\u306eCPU\u3060\u3051\u304cinsert\u95a2\u6570\u3092\u5b9f\u884c\u51fa\u6765\u308b\u3002
\n\u305d\u3046\u306a\u308b\u3068\u4e0a\u3067\u8aac\u660e\u3057\u305f\u3088\u3046\u306a\u7af6\u5408\u72b6\u614b\u306f\u8d77\u304d\u306a\u304f\u306a\u308b\u3002
\n\u4e0a\u306e\u30b3\u30fc\u30c9\u306e\u30ed\u30c3\u30af\u3092\u4f7f\u3063\u305f\u6b63\u3057\u3044\u30d0\u30fc\u30b8\u30e7\u30f3\u306f\u3001\u3044\u304f\u3064\u304b\u306e\u884c\u3092\u8ffd\u52a0\u3057\u305f\u3060\u3051\u3067\u3042\u308b\u3002
\n\uff08\u8ffd\u52a0\u3068\u3044\u3046\u30b3\u30e1\u30f3\u30c8\u304c\u4ed8\u3044\u3066\u308b\u884c\u304c\u8ffd\u52a0\u3057\u305f\u884c\u3067\u3059\u3002\uff09<\/p>\n
struct list {\n  int data;\n  struct list *next;\n};\n\nstruct list *list = 0;\nstruct lock listlock; \/\/ \u8ffd\u52a0\n\nvoid\ninsert(int data)\n{\n  struct list *l;\n  \n  acquire(&listlock); \/\/ \u8ffd\u52a0\n  l = malloc(sizeof *l);\n  l->data = data;\n  l->next = list;\n  list = l;\n  release(&listlock); \/\/ \u8ffd\u52a0\n}<\/pre>\n
\u6211\u3005\u304c\u3001\u300c\u30ed\u30c3\u30af\u304c\u30c7\u30fc\u30bf\u3092\u4fdd\u8b77\u3057\u3066\u3044\u308b\u300d\u3068\u3044\u3046\u8a00\u3046\u3068\u304d\u3001\u6b63\u78ba\u306b\u306f\u300c\u30ed\u30c3\u30af\u304c\u3001\u30c7\u30fc\u30bf\u3078\u9069\u7528\u3059\u308b\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u306e\u3044\u304f\u3064\u304b\u306e\u96c6\u5408\u3092\u4fdd\u8b77\u3057\u3066\u3044\u308b\u300d\u3068\u3044\u3046\u4e8b\u3092\u610f\u5473\u3059\u308b\u3002
\n\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u3068\u306f\u3001\u4e00\u9023\u306e\u64cd\u4f5c\u3092\u901a\u3057\u3066\u7ba1\u7406\u3055\u308c\u3066\u3044\u308b\u30c7\u30fc\u30bf\u69cb\u9020\u306e\u5c5e\u6027\u3067\u3042\u308b\u3002
\n\u5178\u578b\u7684\u306b\u3001\u3072\u3068\u3064\u306e\u64cd\u4f5c\u306f\u3001\u64cd\u4f5c\u304c\u958b\u59cb\u3055\u308c\u305f\u3068\u304d\u306b\u771f\u3068\u306a\u308b\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u306b\u4f9d\u5b58\u3059\u308b\u3075\u308b\u307e\u3044\u3092\u6b63\u3059\u3002
\n\u64cd\u4f5c\u306f\u3001\u4e00\u6642\u7684\u306b\u305d\u306e\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u306b\u9055\u53cd\u3059\u308b\u304c\u3001\u7d42\u4e86\u3059\u308b\u307e\u3048\u306b\u305d\u308c\u3089\u3092\u56de\u5fa9\u3057\u306a\u3051\u308c\u3070\u306a\u3089\u306a\u3044\u3002
\n\u4f8b\u3048\u3070\u30ea\u30f3\u30af\u30ea\u30b9\u30c8\u306e\u5834\u5408\u3001\u305d\u306e\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u306f\u3001\u30ea\u30b9\u30c8\u5185\u306e\u6700\u521d\u306e\u30ce\u30fc\u30c9\u3092\u6307\u3059list\u3068\u3001\u6b21\u306e\u30ce\u30fc\u30c9\u3092\u6307\u3059\u5404\u30ce\u30fc\u30c9\u306enext\u30d5\u30a3\u30fc\u30eb\u30c9\u3067\u3042\u308b\u3002
\ninsert\u306e\u5b9f\u88c5\u306f\u3001\u4e00\u6642\u7684\u306b\u3053\u306e\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u3092\u4fb5\u5bb3\u3059\u308b\u3002
\nmalloc\u306e\u884c\u306f\u3001\u30ea\u30b9\u30c8\u306e\u65b0\u3057\u3044\u8981\u7d20\u3067\u3042\u308bl\u3092\u3001\u30ea\u30b9\u30c8\u306e\u6700\u521d\u306e\u30ce\u30fc\u30c9\u306b\u306a\u308b\u3088\u3046\u751f\u6210\u3059\u308b\u3002
\n\u3057\u304b\u3057\u3053\u306e\u6642\u70b9\u3067\u306f\u3001l\u306e\u6b21\u3078\u306e\u30dd\u30a4\u30f3\u30bf\u306f\u307e\u3060\u6b21\u306e\u30ce\u30fc\u30c9\u3092\u5dee\u3057\u3066\u306f\u304a\u3089\u305a\uff08\u305d\u308c\u306fl->next = list;\u306e\u884c\u3067\u884c\u308f\u308c\u308b\uff09\u3001list\u306f\u307e\u3060l\u3092\u5dee\u3057\u3066\u306f\u3044\u306a\u3044\uff08\u305d\u308c\u306flist = l;\u306e\u884c\u3067\u884c\u308f\u308c\u308b\uff09\u3002
\n\u6211\u3005\u304c\u4e0a\u8a18\u3067\u8abf\u67fb\u3057\u305f\u7af6\u5408\u72b6\u614b\u306f\u3001\u4e00\u6642\u7684\u306b\u4fb5\u5bb3\u3055\u308c\u3066\u3044\u308b\u9593\u3001\u305d\u306e\u30ea\u30b9\u30c8\u306e\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u306b\u4f9d\u5b58\u3057\u305f\u30b3\u30fc\u30c9\u30922\u756a\u76ee\u306eCPU\u304c\u5b9f\u884c\u3059\u308b\u3053\u3068\u306b\u3088\u3063\u3066\u3001\u767a\u751f\u3057\u305f\u3002
\n\u30ed\u30c3\u30af\u3092\u6b63\u3057\u304f\u4f7f\u3048\u3070\u3001\u4e00\u5ea6\u306b\u3072\u3068\u3064\u306eCPU\u3060\u3051\u304c\u30c7\u30fc\u30bf\u69cb\u9020\u4e0a\u3067\u64cd\u4f5c\u3059\u308b\u3053\u3068\u3092\u78ba\u5b9f\u306b\u3067\u304d\u3001\u305d\u306e\u7d50\u679c\u3001\u30c7\u30fc\u30bf\u69cb\u9020\u306e\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u304c\u4e2d\u9014\u534a\u7aef\u306a\u72b6\u614b\u306e\u3068\u304d\u306b\u3001\u4ed6\u306eCPU\u304c\u305d\u306e\u30c7\u30fc\u30bf\u69cb\u9020\u3092\u64cd\u4f5c\u3059\u308b\u3053\u3068\u306f\u306a\u304f\u306a\u308b\u3060\u308d\u3046\u3002<\/p>\n
\u611f\u60f3<\/h3>\n
\u30ed\u30c3\u30af\u306e\u4f7f\u3044\u65b9\u3092\u8efd\u304f\u3068\u3044\u3063\u305f\u3068\u3053\u308d\u3067\u3057\u3087\u3046\u304b\u3002
\n\u30b5\u30f3\u30d7\u30eb\u306e\u30b3\u30fc\u30c9\u81ea\u4f53\u306f\u3001\u30e6\u30fc\u30b6\u7a7a\u9593\u306e\u30d7\u30ed\u30b0\u30e9\u30e0\u3067\u30ed\u30c3\u30af\u3092\u4f7f\u3046\u3068\u304d\u306e\u30b3\u30fc\u30c9\u3068\u5168\u304f\u540c\u3058\u3067\u3059\u306d\u3002<\/p>\n
\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u306f\u8a33\u304c\u96e3\u3057\u3044\u306e\u3067\u305d\u306e\u307e\u307e\u3067\u3059\u304c\u3001\u3053\u3053\u3067\u3044\u3046\u30a4\u30f3\u30d0\u30ea\u30a2\u30f3\u30c8\u306f\u30c7\u30fc\u30bf\u69cb\u9020\u3068\u304b\u5f62\u5f0f\u3068\u304b\u4e00\u8cab\u6027\u3068\u304b\u305d\u3046\u3044\u3063\u305f\u611f\u3058\u306e\u610f\u5473\u304b\u3068\u601d\u3044\u307e\u3059\u3002<\/p>\n
\u4eca\u56de\u3001\u7279\u306b\u6700\u5f8c\u306e\u6bb5\u843d\u304c\u96e3\u3057\u3044\u3067\u3059\u3002
\n\u3053\u306e\u30c6\u30ad\u30b9\u30c8\u3084\u3063\u3066\u308b\u3068\u3001\u62bd\u8c61\u7684\u3067\u8a00\u3044\u56de\u3057\u3082\u5fae\u5999\u3067typo\u304c\u3042\u3063\u3066\u3068\u3066\u3082\u5206\u304b\u308a\u3065\u3089\u3044\u7bc0\u3084\u6bb5\u843d\u306b\u305f\u307e\u306b\u51fa\u304f\u308f\u3057\u307e\u3059\u3002
\n\u62c5\u5f53\u8005\u306e\u9055\u3044\u3067\u3057\u3087\u3046\u304b\u3002<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[32],"tags":[405],"class_list":["post-1415","post","type-post","status-publish","format-standard","hentry","category-tech","tag-xv6"],"_links":{"self":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/posts\/1415","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/comments?post=1415"}],"version-history":[{"count":0,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/posts\/1415\/revisions"}],"wp:attachment":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/media?parent=1415"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/categories?post=1415"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/tags?post=1415"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}