{"id":429358,"date":"2021-04-18T04:22:20","date_gmt":"2021-04-17T20:22:20","guid":{"rendered":"http:\/\/4563.org\/?p=429358"},"modified":"2021-04-19T04:17:45","modified_gmt":"2021-04-18T20:17:45","slug":"go-%e4%b9%8b-waitgroup-%e5%ba%95%e5%b1%82%e5%ae%9e%e7%8e%b0","status":"publish","type":"post","link":"http:\/\/4563.org\/?p=429358","title":{"rendered":"Go \u4e4b WaitGroup \u5e95\u5c42\u5b9e\u73b0"},"content":{"rendered":"
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Go \u4e4b WaitGroup \u5e95\u5c42\u5b9e\u73b0 <\/h1>\n

<\/p>\n

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\u8cc7\u6df1\u5927\u4f6c : hetiansu5 <\/span> <\/i> 7<\/span> <\/div>\n
<\/div>\n<\/p><\/div>\n<\/p><\/div>\n<\/p><\/div>\n
<\/p>\n

WaitGroup<\/h1>\n

<\/p>\n

WaitGroup \u7528\u4e8e\u7b49\u5f85\u4e00\u7ec4\u7ebf\u7a0b\u7684\u7ed3\u675f\uff0c\u7236\u7ebf\u7a0b\u8c03\u7528 Add \u6765\u589e\u52a0\u7b49\u5f85\u7684\u7ebf\u7a0b\u6570\uff0c\u88ab\u7b49\u5f85\u7684\u7ebf\u7a0b\u5728\u7ed3\u675f\u540e\u8c03\u7528 Done \u6765\u5c06\u7b49\u5f85\u7ebf\u7a0b\u6570\u51cf 1\uff0c\u7236\u7ebf\u7a0b\u901a\u8fc7\u8c03\u7528 Wait \u963b\u585e\u7b49\u5f85\u6240\u6709\u7ed3\u675f\uff08\u8ba1\u6570\u5668\u6e05\u96f6\uff09\u540e\u8fdb\u884c\u5524\u9192\u3002<\/p>\n

\u6e90\u7801\u4f4d\u7f6e<\/h2>\n

WaitGroup \u7684\u6e90\u7801\u5728 SDK \u5305\u7684\u8def\u5f84\u4e3asrc\/sync\/waitgroup.go<\/code>\u3002<\/p>\n

\u6570\u636e\u7ed3\u6784<\/h2>\n
type WaitGroup struct {  noCopy noCopy  state1 [3]uint32 } <\/code><\/pre>\n
1.noCopy noCopy<\/p>\n
noCopy \u8fd9\u4e2a\u4e3b\u8981\u7528\u6765\u9650\u5236\u4e0d\u80fd\u8fdb\u884c copy\uff0c\u8fd9\u91cc\u662f\u4e3a\u4e86\u907f\u514d copy \u540e\u7684 waitGroup \u5e76\u53d1\u4f7f\u7528\u540e\uff0c\u53ef\u80fd\u4f1a\u4e0e\u539f waitGroup \u51fa\u73b0\u5f02\u5e38\u800c panic \u3002<\/p>\n
2.state1 [3]unit32<\/p>\n
\u6570\u7ec4\u7684\u4e09\u4e2a\u5143\u7d20\uff08\u975e\u987a\u5e8f\uff09\uff1a<\/p>\n
    \n
  • counter \u901a\u8fc7 Add()\u8bbe\u7f6e\u7684\u5b50 goroutine \u7684\u6570\u91cf\uff0c\u5373\u88ab\u7b49\u5f85\u7ebf\u7a0b\u8ba1\u6570<\/li>\n
  • waiter \u901a\u8fc7 Wait()\u9677\u5165\u963b\u585e\u7684\u7b49\u5f85\u8005\u8ba1\u6570<\/li>\n
  • semap \u4fe1\u53f7\u91cf\uff0c\u7528\u4e8e\u5524\u9192\u963b\u585e waiter<\/li>\n<\/ul>\n
    \u8fd9\u91cc\u9700\u8981\u6ce8\u610f\u4e00\u4e0b couter \u3001waiter \u3001semap \u5e76\u4e0d\u662f\u987a\u5e8f\u5b58\u50a8\u7684\uff0c64bit \u64cd\u4f5c\u7cfb\u7edf\u7684\u539f\u5b50\u64cd\u4f5c\u9700\u8981\u4fdd\u8bc1 64bit \u7684\u5185\u5b58\u5bf9\u9f50\uff0c\u5728\u8bbe\u8ba1\u4e0a\u6211\u4eec\u9700\u8981\u4fdd\u8bc1 couter \u548c waiter \u7684\u64cd\u4f5c\u539f\u5b50\u6027\u3002\u5982\u679c\u6570\u7ec4\u7684\u9996\u5143\u7d20\u5730\u5740\u80fd\u88ab 8 \u6574\u9664\uff0c\u5219 counter \u548c waiter \u521a\u597d\u53ef\u4ee5\u5728\u540c\u4e00\u5757\u539f\u5b50\u64cd\u4f5c\u7684 64bit \u5185\u5b58\u4e0a\uff0c\u6240\u4ee5\u53d6\u6570\u7ec4\u524d\u4e24\u4e2a\u5143\u7d20\u5206\u522b\u8868\u793a couter \u548c waiter \uff1b\u5982\u679c\u4e0d\u80fd\u88ab 8 \u6574\u9664\uff08\u6839\u636e\u5185\u5b58\u5bf9\u9f50\u7684\u539f\u7406\uff0c\u5730\u5740\u5fc5\u7136\u662f 4 \u7684\u500d\u6570\uff09\uff0c\u5219\u53d6\u6570\u7ec4\u540e\u4e24\u4e2a\u3002<\/p>\n
    \/\/ \u6839\u636e\u5185\u5b58\u5bf9\u9f50\u65b9\u5f0f\u7684\u4e0d\u540c\uff0c\u8fd4\u56de statep(couter \u5360\u7528\u9ad8 32bit \u548c waiter \u5360\u7528\u4f4e 32bit)\u548c semap \u7684\u5730\u5740 func (wg *WaitGroup) state() (statep *uint64, semap *uint32) {  if uintptr(unsafe.Pointer(&wg.state1))%8 == 0 {   return (*uint64)(unsafe.Pointer(&wg.state1)), &wg.state1[2]  } else {   return (*uint64)(unsafe.Pointer(&wg.state1[1])), &wg.state1[0]  } } <\/code><\/pre>\n
    \"Go<\/p>\n
    \u516c\u5171\u65b9\u6cd5<\/h2>\n
    func (wg *WaitGroup) Add(delta int) \/\/\u589e\u52a0 waitGroup \u5b50 goruntine \u8ba1\u6570\u503c func (wg *WaitGroup) Done() \/\/\u5f53\u5b50 goruntine \u5b8c\u6210\u540e\uff0c\u5c06\u8ba1\u6570\u5668-1 func (wg *WaitGroup) Wait() \/\/\u8c03\u7528\u6b64\u65b9\u6cd5\u7684 goruntine\uff0c\u963b\u585e\u7b49\u5f85\u8ba1\u6570\u503c\u4e3a 0 <\/code><\/pre>\n
    \u4ee5\u4e0b\u65b9\u6cd5\u53bb\u9664\u4e86 race \u7ade\u4e89\u68c0\u67e5\u7684\u6e90\u4ee3\u7801\u3002<\/p>\n
    Add<\/h3>\n
    \u64cd\u4f5c counter \u8ba1\u6570\u503c\u52a0\u51cf\u3002<\/p>\n
      \n
    • \u5f53 counter \u589e\u52a0\u65f6\uff0c\u76f4\u63a5 return<\/li>\n
    •  \u5f53 counter \u51cf\u5c11\u65f6, \u5224\u65ad\u6761\u4ef6\uff1acounter > 0 || waiter == 0\n
        \n
      • true \u65f6\uff0c\u76f4\u63a5 return<\/li>\n
      • false \uff08\u7b49\u5f85\u7ebf\u7a0b\u90fd\u5b8c\u6210\u4e14\u6709\u7b49\u5f85\u8005\uff09\u65f6\uff0cstatep \u590d\u4f4d\u4e3a 0\uff0c\u901a\u8fc7 semap \u4fe1\u53f7\u91cf\u5524\u9192\u6240\u6709\u7b49\u5f85\u8005<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
        func (wg *WaitGroup) Add(delta int) {  \/\/\u4ece\u6570\u7ec4\u4e2d\u62ff\u5230 stetep \uff08 counter+waiter \u7684\u7ec4\u5408\uff09\u548c semap \u4fe1\u53f7\u91cf\u7684\u5185\u5b58\u5730\u5740  statep, semap := wg.state()  \/\/stetep \u539f\u5b50\u52a0\u64cd\u4f5c\uff0c\u9ad8\u4f4d 32bit \u662f counter,\u5b9e\u9645 counter+1  state := atomic.AddUint64(statep, uint64(delta)<<32)  \/\/state \u7684\u9ad8\u4f4d 32bit\uff0c\u8868\u793a couter \u7684\u8ba1\u6570\u503c  v := int32(state >> 32)  \/\/state \u7684\u4f4e\u4f4d 32bit\uff0c\u8868\u793a waiter \u7684\u7b49\u5f85\u8005\u6570\u91cf  w := uint32(state)  \/\/ couter \u4e0d\u80fd\u5c0f\u4e8e 0  if v < 0 {   panic(\"sync: negative WaitGroup counter\")  }  \/\/ \u9700\u8981\u907f\u514d\u9519\u8bef\u64cd\u4f5c\uff1aAdd \u548c Wait \u5e76\u53d1\u64cd\u4f5c\uff0c\u5426\u5219\u4f1a panic  if w != 0 && delta > 0 && v == int32(delta) {   panic(\"sync: WaitGroup misuse: Add called concurrently with Wait\")  }  \/\/ \u5982\u679c\u8fd8\u6709\u7b49\u5f85\u7ebf\u7a0b\u672a\u5b8c\u6210\u6216\u8005\u5e76\u6ca1\u6709\u7b49\u5f85\u8005\uff0c\u76f4\u63a5 return  if v > 0 || w == 0 {   return  }  \/\/ \u9700\u8981\u907f\u514d\u9519\u8bef\u64cd\u4f5c\uff1aAdd \u548c Wait \u5e76\u53d1\u64cd\u4f5c\uff0c\u5426\u5219\u4f1a panic  if *statep != state {   panic(\"sync: WaitGroup misuse: Add called concurrently with Wait\")  }  \/\/ \u5c06 statep \u590d\u4f4d\u4e3a 0 \uff08 counter \u548c waiter \u90fd\u7f6e\u4e3a 0 \uff09  *statep = 0  \/\/ \u6709\u591a\u5c11\u4e2a\u7b49\u5f85\u8005\u5c31\u5f80 semap \u5faa\u73af\u53d1\u4fe1\u53f7\u91cf\uff08\u5176\u5b9e\u5c31\u662f semap+1 \uff09\uff0cWait \u7b49\u5f85\u6709\u4e00\u4e2a\u8c03\u7528 \/\/ runtime_Semacquire(semap)\u5c31\u662f\u5728\u7b49\u5f85\u8fd9\u4e2a\u4fe1\u53f7\u91cf  for ; w != 0; w-- {   runtime_Semrelease(semap, false, 0)  } } <\/code><\/pre>\n
        Done<\/h3>\n
        \u88ab\u7b49\u5f85\u7ebf\u7a0b\u5b8c\u6210\u540e\u8c03\u7528 Done\uff0c\u5c06 counter \u8ba1\u6570-1\uff0c\u8868\u793a\u7ebf\u7a0b\u7ed3\u675f<\/p>\n
        func (wg *WaitGroup) Done() {  wg.Add(-1) } <\/code><\/pre>\n
        Wait<\/h3>\n
        \u4e3b\u7ebf\u7a0b\u5faa\u73af\u5bf9 waiter \u539f\u5b50\u64cd\u4f5c+1 \u76f4\u5230\u6210\u529f\u540e\uff0c\u7136\u540e\u963b\u585e\u7b49\u5f85 semap \u4fe1\u53f7\u91cf\u800c\u88ab\u5524\u9192\uff0c\u6700\u540e return<\/p>\n
        func (wg *WaitGroup) Wait() {  \/\/ \u4ece\u6570\u7ec4\u4e2d\u62ff\u5230 stetep \uff08 counter+waiter \u7684\u7ec4\u5408\uff09\u548c semap \u4fe1\u53f7\u91cf\u7684\u5185\u5b58\u5730\u5740  statep, semap := wg.state()  for {   \/\/\u4ece\u5185\u5b58\u603b\u7ebf\u4e2d\u52a0\u8f7d\u6700\u65b0\u7684 statep \u503c   state := atomic.LoadUint64(statep)   \/\/state \u7684\u9ad8\u4f4d 32bit\uff0c\u8868\u793a couter \u7684\u8ba1\u6570\u503c   v := int32(state >> 32)   \/\/state \u7684\u4f4e\u4f4d 32bit\uff0c\u8868\u793a waiter \u7684\u7b49\u5f85\u8005\u6570\u91cf   w := uint32(state)   \/\/\u5982\u679c couter \u4e3a 0\uff0c\u8868\u793a\u5f53\u524d\u5df2\u7ecf\u6ca1\u6709\u5728\u8fd0\u884c\u7684\u7b49\u5f85\u7ebf\u7a0b\u4e86   if v == 0 {    return   }   \/\/ CAS \u64cd\u4f5c statep+1\uff0c\u4f4e\u4f4d\u5c5e\u4e8e waiter,\u5373 waiter+1   if atomic.CompareAndSwapUint64(statep, state, state+1) {    \/\/ CAS \u64cd\u4f5c\u6210\u529f\u540e\uff0c\u963b\u585e\u7b49\u5f85 semap \u4fe1\u53f7\u4e3a\u975e\u96f6\uff0c\u7ade\u4e89\u5230\u4f1a\u5c06 semap-1\uff0c\u5e76\u5524\u9192\u7ebf\u7a0b    runtime_Semacquire(semap)    if *statep != 0 {     panic(\"sync: WaitGroup is reused before previous Wait has returned\")    }    return   }   \/\/ CAS \u64cd\u4f5c\u5931\u8d25\u4e86\uff0c\u91cd\u65b0\u8fdb\u5165\u5faa\u73af  } } <\/code><\/pre>\n<\/p><\/div>\n
         \u5927\u4f6c\u6709\u8a71\u8aaa<\/b> (4<\/span>)        <\/div>\n
         <\/div>\n<\/p><\/div>\n<\/p><\/div>\n
          \n
        • \n
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           \u8cc7\u6df1\u5927\u4f6c : makdon <\/span>  <\/div>\n
           <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                       \u62c9\u5230\u6700\u540e\u7adf\u7136\u6ca1\u6709\u516c\u4f17\u53f7 \/\u535a\u5ba2 \/\u57f9\u8bad\u73ed \/\u62db\u8058                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
        • \n
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           \u8cc7\u6df1\u5927\u4f6c : raaaaaar <\/span>  <\/div>\n
           <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                       \u6700\u8fd1\u5b66\u4e86\u64cd\u4f5c\u7cfb\u7edf\uff0c\u53d1\u73b0\u5c31\u662f\u4e2a\u4e8c\u5143\u4fe1\u53f7\u91cf\u3002\u3002                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
        • \n
          \n
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           \u4e3b<\/span> \u8cc7\u6df1\u5927\u4f6c : hetiansu5 <\/span>  <\/div>\n
           <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                       @makdon \u54c8\u54c8\uff0c\u5355\u7eaf\u8f93\u51fa\u800c\u5df2\uff0c\u53d8\u76f8\u7684\u52a0\u6df1\u7406\u89e3                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
        • \n
          \n
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           \u8cc7\u6df1\u5927\u4f6c : kuro1 <\/span>  <\/div>\n
           <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                       \u62c9\u5230\u6700\u540e\u7adf\u7136\u6ca1\u6709\u516c\u4f17\u53f7 \/\u535a\u5ba2 \/\u57f9\u8bad\u73ed \/\u62db\u8058+1                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
        • \n","protected":false},"excerpt":{"rendered":"
          Go \u4e4b WaitGroup \u5e95\u5c42…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[],"tags":[],"_links":{"self":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts\/429358"}],"collection":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=429358"}],"version-history":[{"count":1,"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts\/429358\/revisions"}],"predecessor-version":[{"id":429362,"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts\/429358\/revisions\/429362"}],"wp:attachment":[{"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=429358"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=429358"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=429358"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}