{"id":117864,"date":"2026-10-25T18:40:25","date_gmt":"2026-10-25T10:40:25","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/117864.html"},"modified":"2026-10-25T18:40:25","modified_gmt":"2026-10-25T10:40:25","slug":"%e7%ae%a1%e7%a8%8b%e6%98%af%e6%80%8e%e4%b9%88%e5%ae%9e%e7%8e%b0%e7%9a%84%ef%bc%9a%e4%bb%8e%e6%93%8d%e4%bd%9c%e7%b3%bb%e7%bb%9f%e5%86%85%e6%a0%b8%e5%88%b0-hotspot-%e5%af%b9%e8%b1%a1%e7%9b%91%e8%a7%86","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/117864.html","title":{"rendered":"\u7ba1\u7a0b\u662f\u600e\u4e48\u5b9e\u73b0\u7684\uff1a\u4ece\u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u5230 HotSpot \u5bf9\u8c61\u76d1\u89c6\u5668"},"content":{"rendered":"

English version: How Monitors Are Implemented: From the OS Kernel to the HotSpot ObjectMonitor<\/p>\n

\u59ca\u59b9\u7bc7 \u4ece PV \u64cd\u4f5c\u3001\u7ba1\u7a0b\u5230\u73b0\u4ee3 Java \u5e76\u53d1 \u8bb2\u7684\u662f\u7ba1\u7a0b\u662f\u4ec0\u4e48：\u5171\u4eab\u6570\u636e + \u8fc7\u7a0b + \u9690\u5f0f\u4e92\u65a5 + \u6761\u4ef6\u53d8\u91cf，\u4ee5\u53ca Hoare \/ Mesa \u4e24\u79cd\u5524\u9192\u8bed\u4e49\u3002\u672c\u6587\u53ea\u56de\u7b54\u4e0b\u4e00\u4e2a\u95ee\u9898：\u5b83\u662f\u600e\u4e48\u505a\u51fa\u6765\u7684\u2014\u2014\u4ece\u4e00\u6761 CPU \u539f\u5b50\u6307\u4ee4\u5f00\u59cb，\u7ecf\u8fc7 Linux \u5185\u6838\u7684\u7b49\u5f85\u961f\u5217\u548c futex，\u4e00\u76f4\u5230 HotSpot \u91cc synchronized \u80cc\u540e\u7684\u5bf9\u8c61\u5934\u548c ObjectMonitor\u3002<\/p>\n

\u7f29\u5199\u5bf9\u7167\u8868<\/h3>\n\n\u7f29\u5199\u82f1\u6587\u5168\u79f0\u4e2d\u6587<\/tr>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
OS<\/td>\nOperating System<\/td>\n\u64cd\u4f5c\u7cfb\u7edf<\/td>\n<\/tr>\n
CPU<\/td>\nCentral Processing Unit<\/td>\n\u4e2d\u592e\u5904\u7406\u5668<\/td>\n<\/tr>\n
CAS<\/td>\nCompare-And-Swap<\/td>\n\u6bd4\u8f83\u5e76\u4ea4\u6362<\/td>\n<\/tr>\n
TAS<\/td>\nTest-And-Set<\/td>\n\u6d4b\u8bd5\u5e76\u7f6e\u4f4d<\/td>\n<\/tr>\n
LL\/SC<\/td>\nLoad-Linked \/ Store-Conditional<\/td>\n\u94fe\u63a5\u52a0\u8f7d \/ \u6761\u4ef6\u5b58\u50a8<\/td>\n<\/tr>\n
MCS<\/td>\nMellor-Crummey and Scott（queue lock）<\/td>\nMCS \u961f\u5217\u9501<\/td>\n<\/tr>\n
futex<\/td>\nFast Userspace muTEX<\/td>\nLinux \u5feb\u901f\u7528\u6237\u6001\u4e92\u65a5\u91cf<\/td>\n<\/tr>\n
NPTL<\/td>\nNative POSIX Thread Library<\/td>\nglibc \u7684\u539f\u751f POSIX \u7ebf\u7a0b\u5e93<\/td>\n<\/tr>\n
POSIX<\/td>\nPortable Operating System Interface<\/td>\n\u53ef\u79fb\u690d\u64cd\u4f5c\u7cfb\u7edf\u63a5\u53e3<\/td>\n<\/tr>\n
JVM<\/td>\nJava Virtual Machine<\/td>\nJava \u865a\u62df\u673a<\/td>\n<\/tr>\n
JDK<\/td>\nJava Development Kit<\/td>\nJava \u5f00\u53d1\u5de5\u5177\u5305<\/td>\n<\/tr>\n
JEP<\/td>\nJDK Enhancement Proposal<\/td>\nJDK \u589e\u5f3a\u63d0\u6848<\/td>\n<\/tr>\n
JUC<\/td>\njava.util.concurrent<\/td>\nJava \u5e76\u53d1\u5de5\u5177\u5305<\/td>\n<\/tr>\n
AQS<\/td>\nAbstractQueuedSynchronizer<\/td>\n\u62bd\u8c61\u961f\u5217\u540c\u6b65\u5668<\/td>\n<\/tr>\n
GC<\/td>\nGarbage Collection<\/td>\n\u5783\u573e\u56de\u6536<\/td>\n<\/tr>\n
IPI<\/td>\nInter-Processor Interrupt<\/td>\n\u5904\u7406\u5668\u95f4\u4e2d\u65ad<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

0. \u5148\u62c6\u95ee\u9898：\u7ba1\u7a0b\u8981\u89e3\u51b3\u7684\u4e09\u4ef6\u4e8b<\/h3>\n

\u4e0d\u7ba1\u5728\u54ea\u4e00\u5c42\u5b9e\u73b0，\u7ba1\u7a0b\u90fd\u8981\u56de\u7b54\u4e09\u4e2a\u673a\u5236\u95ee\u9898：<\/p>\n

  • \u4e92\u65a5：\u600e\u4e48\u4fdd\u8bc1\u540c\u4e00\u65f6\u523b\u53ea\u6709\u4e00\u4e2a\u7ebf\u7a0b\u5728\u7ba1\u7a0b\u91cc？<\/li>\n
  • \u6761\u4ef6\u7b49\u5f85：wait(c) \u8981"\u91ca\u653e\u9501 + \u7761\u7720"，signal(c) \u8981"\u5524\u9192\u4e00\u4e2a"\u2014\u2014\u4e24\u6b65\u4e4b\u95f4\u5982\u679c\u88ab\u63d2\u961f，\u4fe1\u53f7\u5c31\u4e22\u4e86（\u4e22\u5931\u5524\u9192，lost wakeup）\u3002\u600e\u4e48\u907f\u514d？<\/li>\n
  • \u963b\u585e\u4e0e\u5524\u9192：\u62a2\u4e0d\u5230\u9501\u3001\u6761\u4ef6\u4e0d\u6210\u7acb\u65f6，\u7ebf\u7a0b\u600e\u4e48\u771f\u7684"\u505c\u4e0b\u6765"\u4e0d\u5360 CPU，\u53c8\u600e\u4e48\u88ab\u53eb\u9192？<\/li>\n

    \u4e0b\u9762\u6bcf\u4e00\u5c42\u7684\u8bbe\u8ba1，\u90fd\u662f\u5bf9\u8fd9\u4e09\u4e2a\u95ee\u9898\u7684\u4e00\u79cd\u56de\u7b54\u3002<\/p>\n

    #mermaid-svg-ERrqDGjyT79gUrC6{font-family:\\”trebuchet ms\\”,verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#mermaid-svg-ERrqDGjyT79gUrC6 .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#mermaid-svg-ERrqDGjyT79gUrC6 .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#mermaid-svg-ERrqDGjyT79gUrC6 .error-icon{fill:#552222;}#mermaid-svg-ERrqDGjyT79gUrC6 .error-text{fill:#552222;stroke:#552222;}#mermaid-svg-ERrqDGjyT79gUrC6 .edge-thickness-normal{stroke-width:1px;}#mermaid-svg-ERrqDGjyT79gUrC6 .edge-thickness-thick{stroke-width:3.5px;}#mermaid-svg-ERrqDGjyT79gUrC6 .edge-pattern-solid{stroke-dasharray:0;}#mermaid-svg-ERrqDGjyT79gUrC6 .edge-thickness-invisible{stroke-width:0;fill:none;}#mermaid-svg-ERrqDGjyT79gUrC6 .edge-pattern-dashed{stroke-dasharray:3;}#mermaid-svg-ERrqDGjyT79gUrC6 .edge-pattern-dotted{stroke-dasharray:2;}#mermaid-svg-ERrqDGjyT79gUrC6 .marker{fill:#333333;stroke:#333333;}#mermaid-svg-ERrqDGjyT79gUrC6 .marker.cross{stroke:#333333;}#mermaid-svg-ERrqDGjyT79gUrC6 svg{font-family:\\”trebuchet ms\\”,verdana,arial,sans-serif;font-size:16px;}#mermaid-svg-ERrqDGjyT79gUrC6 p{margin:0;}#mermaid-svg-ERrqDGjyT79gUrC6 .label{font-family:\\”trebuchet ms\\”,verdana,arial,sans-serif;color:#333;}#mermaid-svg-ERrqDGjyT79gUrC6 .cluster-label text{fill:#333;}#mermaid-svg-ERrqDGjyT79gUrC6 .cluster-label span{color:#333;}#mermaid-svg-ERrqDGjyT79gUrC6 .cluster-label span p{background-color:transparent;}#mermaid-svg-ERrqDGjyT79gUrC6 .label text,#mermaid-svg-ERrqDGjyT79gUrC6 span{fill:#333;color:#333;}#mermaid-svg-ERrqDGjyT79gUrC6 .node rect,#mermaid-svg-ERrqDGjyT79gUrC6 .node circle,#mermaid-svg-ERrqDGjyT79gUrC6 .node ellipse,#mermaid-svg-ERrqDGjyT79gUrC6 .node polygon,#mermaid-svg-ERrqDGjyT79gUrC6 .node path{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#mermaid-svg-ERrqDGjyT79gUrC6 .rough-node .label text,#mermaid-svg-ERrqDGjyT79gUrC6 .node .label text,#mermaid-svg-ERrqDGjyT79gUrC6 .image-shape .label,#mermaid-svg-ERrqDGjyT79gUrC6 .icon-shape .label{text-anchor:middle;}#mermaid-svg-ERrqDGjyT79gUrC6 .node .katex path{fill:#000;stroke:#000;stroke-width:1px;}#mermaid-svg-ERrqDGjyT79gUrC6 .rough-node .label,#mermaid-svg-ERrqDGjyT79gUrC6 .node .label,#mermaid-svg-ERrqDGjyT79gUrC6 .image-shape .label,#mermaid-svg-ERrqDGjyT79gUrC6 .icon-shape .label{text-align:center;}#mermaid-svg-ERrqDGjyT79gUrC6 .node.clickable{cursor:pointer;}#mermaid-svg-ERrqDGjyT79gUrC6 .root .anchor path{fill:#333333!important;stroke-width:0;stroke:#333333;}#mermaid-svg-ERrqDGjyT79gUrC6 .arrowheadPath{fill:#333333;}#mermaid-svg-ERrqDGjyT79gUrC6 .edgePath .path{stroke:#333333;stroke-width:2.0px;}#mermaid-svg-ERrqDGjyT79gUrC6 .flowchart-link{stroke:#333333;fill:none;}#mermaid-svg-ERrqDGjyT79gUrC6 .edgeLabel{background-color:rgba(232,232,232, 0.8);text-align:center;}#mermaid-svg-ERrqDGjyT79gUrC6 .edgeLabel p{background-color:rgba(232,232,232, 0.8);}#mermaid-svg-ERrqDGjyT79gUrC6 .edgeLabel rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#mermaid-svg-ERrqDGjyT79gUrC6 .labelBkg{background-color:rgba(232, 232, 232, 0.5);}#mermaid-svg-ERrqDGjyT79gUrC6 .cluster rect{fill:#ffffde;stroke:#aaaa33;stroke-width:1px;}#mermaid-svg-ERrqDGjyT79gUrC6 .cluster text{fill:#333;}#mermaid-svg-ERrqDGjyT79gUrC6 .cluster span{color:#333;}#mermaid-svg-ERrqDGjyT79gUrC6 div.mermaidTooltip{position:absolute;text-align:center;max-width:200px;padding:2px;font-family:\\”trebuchet ms\\”,verdana,arial,sans-serif;font-size:12px;background:hsl(80, 100%, 96.2745098039%);border:1px solid #aaaa33;border-radius:2px;pointer-events:none;z-index:100;}#mermaid-svg-ERrqDGjyT79gUrC6 .flowchartTitleText{text-anchor:middle;font-size:18px;fill:#333;}#mermaid-svg-ERrqDGjyT79gUrC6 rect.text{fill:none;stroke-width:0;}#mermaid-svg-ERrqDGjyT79gUrC6 .icon-shape,#mermaid-svg-ERrqDGjyT79gUrC6 .image-shape{background-color:rgba(232,232,232, 0.8);text-align:center;}#mermaid-svg-ERrqDGjyT79gUrC6 .icon-shape p,#mermaid-svg-ERrqDGjyT79gUrC6 .image-shape p{background-color:rgba(232,232,232, 0.8);padding:2px;}#mermaid-svg-ERrqDGjyT79gUrC6 .icon-shape .label rect,#mermaid-svg-ERrqDGjyT79gUrC6 .image-shape .label rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#mermaid-svg-ERrqDGjyT79gUrC6 .label-icon{display:inline-block;height:1em;overflow:visible;vertical-align:-0.125em;}#mermaid-svg-ERrqDGjyT79gUrC6 .node .label-icon path{fill:currentColor;stroke:revert;stroke-width:revert;}#mermaid-svg-ERrqDGjyT79gUrC6 :root{–mermaid-font-family:\\”trebuchet ms\\”,verdana,arial,sans-serif;}<\/p>\n

    <\/span><\/p>\n

    <\/span><\/p>\n

    <\/span><\/p>\n

    <\/span><\/p>\n

    <\/p>\n

    \u8bed\u8a00\u5c42：\u7ba1\u7a0b\u8bed\u6cd5synchronized \/ wait \/ notify<\/p>\n

    <\/span><\/p>\n

    <\/p>\n

    \u8fd0\u884c\u65f6\u5c42：HotSpotMark Word + ObjectMonitor<\/p>\n

    <\/span><\/p>\n

    <\/p>\n

    \u7528\u6237\u6001\u7ebf\u7a0b\u5e93：glibc NPTLpthread_mutex \/ pthread_cond<\/p>\n

    <\/span><\/p>\n

    <\/p>\n

    \u5185\u6838：futex \u7cfb\u7edf\u8c03\u7528\u7b49\u5f85\u961f\u5217 + \u8c03\u5ea6\u5668<\/p>\n

    <\/span><\/p>\n

    <\/p>\n

    \u786c\u4ef6：\u539f\u5b50\u6307\u4ee4LOCK CMPXCHG \/ LL-SC+ \u5185\u5b58\u5c4f\u969c<\/p>\n

    <\/span><\/p>\n

    \u8fd9\u5f20\u56fe\u56de\u7b54：\u4e00\u6b21 synchronized \u963b\u585e，\u4ece\u8bed\u8a00\u4e00\u8def\u843d\u5230\u54ea\u4e9b\u5c42？<\/p>\n

    \u7b2c\u4e00\u90e8\u5206：\u64cd\u4f5c\u7cfb\u7edf\u91cc\u7684\u7ba1\u7a0b\u662f\u600e\u4e48\u5b9e\u73b0\u7684<\/h3>\n

    \u5148\u6f84\u6e05\u4e00\u4e2a\u5bb9\u6613\u6df7\u7684\u70b9：\u7ba1\u7a0b\u662f\u8bed\u8a00\u7ed3\u6784，\u4e0d\u662f\u5185\u6838\u5bf9\u8c61\u3002 Linux \u5185\u6838\u91cc\u6ca1\u6709\u4e00\u4e2a\u53eb monitor \u7684\u7cfb\u7edf\u8c03\u7528\u3002Hoare \u548c Brinch Hansen \u8bbe\u60f3\u7684\u662f：\u7f16\u8bd1\u5668\u770b\u5230 monitor \u5173\u952e\u5b57，\u81ea\u52a8\u5728\u6bcf\u4e2a\u8fc7\u7a0b\u5165\u53e3\u63d2\u5165\u52a0\u9501\u3001\u51fa\u53e3\u63d2\u5165\u89e3\u9501，\u628a wait\/signal \u7f16\u8bd1\u6210\u5bf9\u6761\u4ef6\u53d8\u91cf\u7684\u64cd\u4f5c\u3002\u6240\u4ee5"OS \u91cc\u7684\u7ba1\u7a0b"，\u5b9e\u9645\u662f\u95ee：OS \u63d0\u4f9b\u4e86\u4ec0\u4e48\u539f\u8bed，\u8ba9\u7f16\u8bd1\u5668 \/ \u8fd0\u884c\u65f6\u80fd\u628a\u7ba1\u7a0b\u62fc\u51fa\u6765？ \u7b54\u6848\u662f\u4e24\u6837：\u9501\u548c\u7b49\u5f85\u961f\u5217\u3002<\/p>\n

    1.1 \u4e92\u65a5：\u4e00\u5207\u4ece\u4e00\u6761\u539f\u5b50\u6307\u4ee4\u5f00\u59cb<\/h4>\n

    \u5355\u6838\u65f6\u4ee3：\u4e34\u754c\u533a\u53ea\u4f1a\u88ab\u4e2d\u65ad\u6253\u65ad，\u4e8e\u662f\u8fdb\u5165\u65f6\u5173\u4e2d\u65ad\u3001\u9000\u51fa\u65f6\u5f00\u4e2d\u65ad，\u5c31\u5f97\u5230\u4e86\u4e92\u65a5\u3002\u8fd9\u62db\u5728\u591a\u6838\u4e0a\u5931\u6548\u2014\u2014\u5173\u6389\u7684\u53ea\u662f\u672c\u6838\u7684\u4e2d\u65ad，\u522b\u7684\u6838\u7167\u6837\u8dd1\u3002<\/p>\n

    \u591a\u6838：\u9760\u786c\u4ef6\u63d0\u4f9b"\u8bfb\u2014\u6539\u2014\u5199\u4e0d\u53ef\u5206\u5272"\u7684\u6307\u4ee4：<\/p>\n\n\u6307\u4ee4\u65cf\u4ee3\u8868\u8bed\u4e49<\/tr>\n\n\n\n\n
    TAS \/ \u4ea4\u6362<\/td>\nx86 XCHG<\/td>\n\u539f\u5b50\u5730\u5199\u5165\u65b0\u503c\u5e76\u8fd4\u56de\u65e7\u503c<\/td>\n<\/tr>\n
    CAS<\/td>\nx86 LOCK CMPXCHG<\/td>\n\u5f53\u524d\u503c\u7b49\u4e8e\u671f\u671b\u503c\u624d\u5199\u5165，\u8fd4\u56de\u662f\u5426\u6210\u529f<\/td>\n<\/tr>\n
    LL\/SC<\/td>\nARM LDXR\/STXR（\u6216 ARMv8.1 \u7684 CAS）<\/td>\n\u8bfb\u540e\u82e5\u671f\u95f4\u65e0\u4eba\u5199\u8fc7，\u624d\u5141\u8bb8\u5199\u56de<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    LOCK \u524d\u7f00\u8ba9\u8be5\u6838\u5728\u7f13\u5b58\u4e00\u81f4\u6027\u534f\u8bae\u91cc\u72ec\u5360\u8fd9\u6761\u7f13\u5b58\u884c，\u5176\u4ed6\u6838\u6b64\u523b\u65e0\u6cd5\u4fee\u6539\u5b83；\u540c\u65f6\u8fd9\u4e9b\u6307\u4ee4\u81ea\u5e26\u5185\u5b58\u5c4f\u969c\u8bed\u4e49，\u4fdd\u8bc1\u4e34\u754c\u533a\u5185\u7684\u8bfb\u5199\u4e0d\u4f1a\u88ab\u91cd\u6392\u5230\u9501\u5916\u3002\u6709\u4e86\u5b83，\u6700\u6734\u7d20\u7684\u9501\u2014\u2014\u81ea\u65cb\u9501\u2014\u2014\u53ea\u9700\u51e0\u884c：<\/p>\n

    void<\/span> spin_lock<\/span>(<\/span>int<\/span> *<\/span>l)<\/span> {<\/span> while<\/span> (<\/span>xchg<\/span>(<\/span>l,<\/span> 1<\/span>)<\/span> ==<\/span> 1<\/span>)<\/span> cpu_relax<\/span>(<\/span>)<\/span>;<\/span> }<\/span> \/\/ \u62a2\u4e0d\u5230\u5c31\u539f\u5730\u8f6c<\/span>
    \nvoid<\/span> spin_unlock<\/span>(<\/span>int<\/span> *<\/span>l)<\/span> {<\/span> store_release<\/span>(<\/span>l,<\/span> 0<\/span>)<\/span>;<\/span> }<\/span><\/p>\n

    \u81ea\u65cb\u9501\u89e3\u51b3\u4e86"\u4e92\u65a5"，\u4f46\u6ca1\u89e3\u51b3"\u963b\u585e"：\u62a2\u4e0d\u5230\u7684\u7ebf\u7a0b\u4e00\u76f4\u5728\u70e7 CPU\u3002\u6301\u9501\u65f6\u95f4\u77ed（\u51e0\u5341\u7eb3\u79d2）\u65f6\u8fd9\u53cd\u800c\u6700\u5feb；\u6301\u9501\u65f6\u95f4\u957f\u6216\u6301\u9501\u8005\u88ab\u8c03\u5ea6\u8d70\u65f6，\u5c31\u662f\u7eaf\u6d6a\u8d39\u3002\u6240\u4ee5\u9700\u8981\u7b2c\u4e8c\u6837\u4e1c\u897f\u3002<\/p>\n

    1.2 \u963b\u585e\u4e0e\u5524\u9192：\u5185\u6838\u7684\u7b49\u5f85\u961f\u5217\u548c\u8c03\u5ea6\u5668<\/h4>\n

    \u5185\u6838\u8ba9\u4e00\u4e2a\u7ebf\u7a0b"\u505c\u4e0b\u6765"\u7684\u65b9\u5f0f\u662f：\u628a\u5b83\u7684\u72b6\u6001\u6539\u6210\u7761\u7720，\u4ece\u8fd0\u884c\u961f\u5217\u4e0a\u6458\u4e0b\u6765，\u7136\u540e\u5207\u6362\u5230\u522b\u7684\u7ebf\u7a0b\u3002Linux \u5185\u6838\u91cc\u4e00\u4e2a\u6807\u51c6\u7684"\u7b49\u6761\u4ef6"\u5199\u6cd5\u5982\u4e0b：<\/p>\n

    DEFINE_WAIT<\/span>(<\/span>wait)<\/span>;<\/span>
    \nfor<\/span> (<\/span>;<\/span>;<\/span>)<\/span> {<\/span>
    \n prepare_to_wait<\/span>(<\/span>&<\/span>wq,<\/span> &<\/span>wait,<\/span> TASK_INTERRUPTIBLE)<\/span>;<\/span> \/\/ \u2460 \u5148\u5165\u961f\u5e76\u628a\u81ea\u5df1\u6807\u6210"\u7761\u7720"<\/span>
    \n if<\/span> (<\/span>condition)<\/span> \/\/ \u2461 \u518d\u68c0\u67e5\u6761\u4ef6<\/span>
    \n break<\/span>;<\/span>
    \n schedule<\/span>(<\/span>)<\/span>;<\/span> \/\/ \u2462 \u8ba9\u51fa CPU，\u771f\u6b63\u7761\u4e0b<\/span>
    \n}<\/span>
    \nfinish_wait<\/span>(<\/span>&<\/span>wq,<\/span> &<\/span>wait)<\/span>;<\/span><\/p>\n

    \u5524\u9192\u65b9：<\/p>\n

    condition =<\/span> true;<\/span>
    \nwake_up<\/span>(<\/span>&<\/span>wq)<\/span>;<\/span> \/\/ \u628a\u961f\u5217\u91cc\u7684\u7ebf\u7a0b\u6807\u56de TASK_RUNNING，\u653e\u56de\u8fd0\u884c\u961f\u5217<\/span><\/p>\n

    \u4e22\u5931\u5524\u9192\u662f\u600e\u4e48\u907f\u514d\u7684？ \u5173\u952e\u5728 \u2460 \u548c \u2461 \u7684\u987a\u5e8f：\u5148\u628a\u81ea\u5df1\u6302\u8fdb\u961f\u5217\u5e76\u6807\u6210\u7761\u7720，\u518d\u68c0\u67e5\u6761\u4ef6\u3002\u5982\u679c\u5524\u9192\u65b9\u6070\u597d\u5728 \u2461 \u548c \u2462 \u4e4b\u95f4\u6267\u884c\u4e86 wake_up，\u5b83\u4f1a\u628a\u672c\u7ebf\u7a0b\u7684\u72b6\u6001\u6539\u56de TASK_RUNNING\u2014\u2014\u4e8e\u662f \u2462 \u7684 schedule() \u53d1\u73b0\u81ea\u5df1\u662f\u53ef\u8fd0\u884c\u7684，\u7acb\u523b\u8fd4\u56de，\u4e0d\u4f1a\u7761\u6b7b\u3002\u53cd\u8fc7\u6765，\u5982\u679c\u5148\u68c0\u67e5\u6761\u4ef6\u518d\u5165\u961f，\u4e2d\u95f4\u90a3\u4e00\u77ac\u95f4\u7684\u5524\u9192\u5c31\u843d\u4e86\u7a7a\u3002<\/p>\n

    \u6302\u8d77\u548c\u5524\u9192\u7684\u7269\u7406\u8fc7\u7a0b：<\/p>\n

      \n
    • \u6302\u8d77：schedule() \u628a\u5f53\u524d\u4efb\u52a1\u79fb\u51fa\u8fd0\u884c\u961f\u5217，context_switch() \u4fdd\u5b58\u5bc4\u5b58\u5668\u3001\u5207\u6362\u5185\u6838\u6808（\u8de8\u8fdb\u7a0b\u65f6\u8fd8\u8981\u5207\u6362\u9875\u8868），CPU \u8f6c\u53bb\u6267\u884c\u522b\u7684\u4efb\u52a1\u3002\u8fd9\u4e2a\u7ebf\u7a0b\u4e0d\u518d\u5360\u7528\u4efb\u4f55 CPU \u65f6\u95f4\u3002<\/li>\n
    • \u5524\u9192：try_to_wake_up() \u628a\u4efb\u52a1\u72b6\u6001\u6539\u4e3a TASK_RUNNING，\u653e\u56de\u67d0\u4e2a CPU \u7684\u8fd0\u884c\u961f\u5217；\u5982\u679c\u76ee\u6807 CPU \u5728\u7a7a\u95f2，\u5c31\u53d1\u4e00\u4e2a IPI（Inter-Processor Interrupt，\u5904\u7406\u5668\u95f4\u4e2d\u65ad）\u628a\u5b83\u53eb\u9192\u3002<\/li>\n<\/ul>\n

      \u6ce8\u610f：\u5524\u9192\u53ea\u662f\u8ba9\u7ebf\u7a0b\u53d8\u5f97\u53ef\u8fd0\u884c，\u4ec0\u4e48\u65f6\u5019\u771f\u6b63\u4e0a CPU \u7531\u8c03\u5ea6\u5668\u51b3\u5b9a\u3002\u8fd9\u6b63\u662f Mesa \u8bed\u4e49\u7684\u7269\u7406\u6765\u6e90\u2014\u2014\u88ab\u5524\u9192\u8005\u6062\u590d\u8fd0\u884c\u65f6，\u6761\u4ef6\u53ef\u80fd\u5df2\u7ecf\u88ab\u522b\u4eba\u6539\u6389\u4e86，\u6240\u4ee5\u5fc5\u987b while \u91cd\u67e5\u3002<\/p>\n

      1.3 \u5185\u6838\u81ea\u5df1\u7684\u7761\u7720\u9501：\u81ea\u65cb + \u6392\u961f\u7684\u6df7\u5408\u4f53<\/h4>\n

      \u5185\u6838\u91cc\u7684 struct mutex \u628a\u4e0a\u9762\u4e24\u6837\u7ec4\u5408\u8d77\u6765，\u5206\u4e09\u6bb5\u8def\u5f84：<\/p>\n\n\u8def\u5f84\u6761\u4ef6\u505a\u6cd5<\/tr>\n\n\n\n\n
      \u5feb\u901f\u8def\u5f84<\/td>\n\u9501\u7a7a\u95f2<\/td>\n\u4e00\u6b21 cmpxchg \u628a owner \u4ece 0 \u6539\u6210\u81ea\u5df1，\u5b8c\u4e8b<\/td>\n<\/tr>\n
      \u4e2d\u95f4\u8def\u5f84<\/td>\n\u9501\u88ab\u5360，\u4f46\u6301\u6709\u8005\u6b63\u5728\u67d0\u4e2a CPU \u4e0a\u8fd0\u884c<\/td>\n\u4e50\u89c2\u81ea\u65cb（\u6392\u5728 MCS \u98ce\u683c\u7684\u961f\u5217\u91cc\u8f6c），\u8d4c\u5b83\u9a6c\u4e0a\u91ca\u653e<\/td>\n<\/tr>\n
      \u6162\u901f\u8def\u5f84<\/td>\n\u6301\u6709\u8005\u7761\u7740\u4e86，\u6216\u81ea\u65cb\u592a\u4e45<\/td>\n\u6302\u8fdb wait_list，schedule() \u7761\u4e0b；\u89e3\u9501\u8005\u8d1f\u8d23\u5524\u9192<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

      \u8fd9\u4e2a"\u5148 CAS\u3001\u518d\u81ea\u65cb\u3001\u6700\u540e\u6392\u961f\u7761\u7720"\u7684\u4e09\u6bb5\u5f0f，\u540e\u9762\u5728 futex\u3001glibc\u3001HotSpot \u91cc\u4f1a\u4e00\u518d\u51fa\u73b0\u3002<\/p>\n

      1.4 \u628a\u7ba1\u7a0b\u62fc\u51fa\u6765：\u7ecf\u5178\u7684"\u7528\u4fe1\u53f7\u91cf\u5b9e\u73b0 Hoare \u7ba1\u7a0b"<\/h4>\n

      \u6709\u4e86\u9501\u548c\u7b49\u5f85\u961f\u5217（\u4fe1\u53f7\u91cf\u5c31\u662f\u4e8c\u8005\u7684\u5c01\u88c5），\u7f16\u8bd1\u5668\u5c31\u80fd\u628a\u7ba1\u7a0b\u7ffb\u8bd1\u51fa\u6765\u3002\u4e0b\u9762\u662f\u6559\u6750\u91cc\u7684\u6807\u51c6\u8bd1\u6cd5，\u5b9e\u73b0\u7684\u662f Hoare \u8bed\u4e49（signal \u540e\u8ba9\u88ab\u5524\u9192\u8005\u7acb\u5373\u8fd0\u884c）：<\/p>\n

      semaphore mutex = 1; \/\/ \u7ba1\u7a0b\u5165\u53e3\u9501
      \nsemaphore next = 0; \/\/ signal \u8005\u8ba9\u51fa\u540e，\u7761\u5728\u8fd9\u91cc
      \nint next_count = 0; \/\/ \u7761\u5728 next \u4e0a\u7684 signal \u8005\u6570\u91cf<\/p>\n

      \u6bcf\u4e2a\u6761\u4ef6\u53d8\u91cf x：
      \nsemaphore x_sem = 0;
      \nint x_count = 0;<\/p>\n

      \u8fc7\u7a0b\u4f53：
      \n P(mutex);
      \n \u2026\u8fc7\u7a0b\u4ee3\u7801\u2026
      \n if (next_count > 0) V(next); \/\/ \u4f18\u5148\u628a\u7ba1\u7a0b\u4ea4\u8fd8\u7ed9\u8ba9\u51fa\u7684 signal \u8005
      \n else V(mutex);<\/p>\n

      x.wait():
      \n x_count++;
      \n if (next_count > 0) V(next); else V(mutex); \/\/ \u91ca\u653e\u7ba1\u7a0b
      \n P(x_sem); \/\/ \u7761\u5728 x \u4e0a
      \n x_count–;<\/p>\n

      x.signal():
      \n if (x_count > 0) {
      \n next_count++;
      \n V(x_sem); \/\/ \u5524\u9192\u4e00\u4e2a x \u4e0a\u7684\u7b49\u5f85\u8005，\u7ba1\u7a0b\u76f4\u63a5\u4ea4\u7ed9\u5b83
      \n P(next); \/\/ \u81ea\u5df1\u8ba9\u51fa，\u7761\u5230 next \u4e0a
      \n next_count–;
      \n }<\/p>\n

      \u8bfb\u8fd9\u6bb5\u4ee3\u7801\u80fd\u770b\u6e05 Hoare \u8bed\u4e49\u7684\u4ee3\u4ef7：\u6bcf\u6b21 signal \u90fd\u8981\u989d\u5916\u4e00\u6b21\u7ebf\u7a0b\u5207\u6362（signal \u8005\u7761\u4e0b\u3001\u88ab\u5524\u9192\u8005\u4e0a\u573a）\u3002Mesa \u8bed\u4e49\u628a x.signal() \u7b80\u5316\u6210"V(x_sem) \u7136\u540e\u7ee7\u7eed\u8dd1"，\u7701\u6389\u90a3\u6b21\u5207\u6362，\u4ee3\u4ef7\u662f\u7b49\u5f85\u8005\u9192\u6765\u540e\u8981\u91cd\u65b0\u68c0\u67e5\u6761\u4ef6\u2014\u2014\u8fd9\u5c31\u662f pthreads \u548c Java \u90fd\u9009 Mesa \u7684\u5de5\u7a0b\u539f\u56e0\u3002<\/p>\n

      1.5 \u7528\u6237\u6001\u7684\u6377\u5f84：futex<\/h4>\n

      \u4e0a\u9762\u7684\u5185\u6838\u673a\u5236\u6709\u4e2a\u95ee\u9898：\u54ea\u6015\u9501\u5b8c\u5168\u6ca1\u4eba\u62a2，\u6bcf\u6b21\u52a0\u9501\u4e5f\u5f97\u9677\u5165\u5185\u6838\u3002\u4e00\u6b21\u7cfb\u7edf\u8c03\u7528\u7684\u6210\u672c\u8fdc\u9ad8\u4e8e\u4e00\u6761\u539f\u5b50\u6307\u4ee4（\u524d\u8005\u901a\u5e38\u5728\u767e\u7eb3\u79d2\u7ea7\u4ee5\u4e0a，\u518d\u52a0\u4e0a\u4e0b\u6587\u5207\u6362\u5c31\u662f\u5fae\u79d2\u7ea7；\u540e\u8005\u65e0\u7ade\u4e89\u65f6\u5728\u7eb3\u79d2\u7ea7）\u3002futex（Fast Userspace muTEX，2002 \u5e74\u8fdb\u5165 Linux 2.5）\u7684\u601d\u8def\u662f：\u9501\u7684\u72b6\u6001\u653e\u5728\u7528\u6237\u5185\u5b58\u91cc，\u53ea\u6709\u771f\u8981\u7761\u89c9\u6216\u771f\u8981\u53eb\u9192\u4eba\u65f6\u624d\u8fdb\u5185\u6838\u3002<\/p>\n

      futex \u53ea\u6709\u4e24\u4e2a\u6838\u5fc3\u64cd\u4f5c：<\/p>\n

        \n
      • futex_wait(addr, expected)：\u5185\u6838\u5728\u6301\u6709\u8be5\u5730\u5740\u5bf9\u5e94\u54c8\u5e0c\u6876\u9501\u7684\u60c5\u51b5\u4e0b\u68c0\u67e5 *addr == expected，\u76f8\u7b49\u624d\u8ba9\u8c03\u7528\u8005\u7761\u4e0b；\u4e0d\u7b49\u5c31\u7acb\u5373\u8fd4\u56de EAGAIN\u3002<\/li>\n
      • futex_wake(addr, n)：\u5524\u9192\u6700\u591a n \u4e2a\u7761\u5728 addr \u4e0a\u7684\u7ebf\u7a0b\u3002<\/li>\n<\/ul>\n

        "\u68c0\u67e5\u503c"\u548c"\u5165\u961f\u7761\u7720"\u5728\u5185\u6838\u91cc\u662f\u539f\u5b50\u7684\u2014\u2014\u8fd9\u4e0e 1.2 \u4e2d"\u5148\u5165\u961f\u518d\u67e5\u6761\u4ef6"\u662f\u540c\u4e00\u4e2a\u9632\u4e22\u5931\u5524\u9192\u7684\u6280\u5de7，\u53ea\u4e0d\u8fc7\u628a"\u6761\u4ef6"\u6362\u6210\u4e86\u4e00\u4e2a\u7528\u6237\u6001\u6574\u6570\u3002<\/p>\n

        Ulrich Drepper \u5728 Futexes Are Tricky \u91cc\u7ed9\u51fa\u7684\u7ecf\u5178\u4e92\u65a5\u9501，\u7528\u4e09\u4e2a\u72b6\u6001：0 \u7a7a\u95f2\u30011 \u5df2\u9501\u65e0\u7b49\u5f85\u8005\u30012 \u5df2\u9501\u4e14\u53ef\u80fd\u6709\u7b49\u5f85\u8005：<\/p>\n

        void<\/span> lock<\/span>(<\/span>int<\/span> *<\/span>f)<\/span> {<\/span>
        \n int<\/span> c =<\/span> cmpxchg<\/span>(<\/span>f,<\/span> 0<\/span>,<\/span> 1<\/span>)<\/span>;<\/span> \/\/ \u5feb\u901f\u8def\u5f84：0 \u2192 1，\u7eaf\u7528\u6237\u6001<\/span>
        \n if<\/span> (<\/span>c !=<\/span> 0<\/span>)<\/span> {<\/span>
        \n if<\/span> (<\/span>c !=<\/span> 2<\/span>)<\/span> c =<\/span> xchg<\/span>(<\/span>f,<\/span> 2<\/span>)<\/span>;<\/span> \/\/ \u6807\u8bb0"\u6709\u4eba\u5728\u7b49"<\/span>
        \n while<\/span> (<\/span>c !=<\/span> 0<\/span>)<\/span> {<\/span>
        \n futex_wait<\/span>(<\/span>f,<\/span> 2<\/span>)<\/span>;<\/span> \/\/ \u6162\u901f\u8def\u5f84：\u8fdb\u5185\u6838\u7761<\/span>
        \n c =<\/span> xchg<\/span>(<\/span>f,<\/span> 2<\/span>)<\/span>;<\/span>
        \n }<\/span>
        \n }<\/span>
        \n}<\/span><\/p>\n

        void<\/span> unlock<\/span>(<\/span>int<\/span> *<\/span>f)<\/span> {<\/span>
        \n if<\/span> (<\/span>atomic_dec<\/span>(<\/span>f)<\/span> !=<\/span> 1<\/span>)<\/span> {<\/span> \/\/ \u539f\u6765\u662f 2：\u53ef\u80fd\u6709\u4eba\u5728\u7b49<\/span>
        \n *<\/span>f =<\/span> 0<\/span>;<\/span>
        \n futex_wake<\/span>(<\/span>f,<\/span> 1<\/span>)<\/span>;<\/span> \/\/ \u8fdb\u5185\u6838\u53eb\u9192\u4e00\u4e2a<\/span>
        \n }<\/span> \/\/ \u539f\u6765\u662f 1：\u65e0\u4eba\u7b49\u5f85，\u7eaf\u7528\u6237\u6001\u8fd4\u56de<\/span>
        \n}<\/span><\/p>\n

        \u7ebf\u7a0b B<\/p>\n

        \u5185\u6838 futex<\/p>\n

        \u7528\u6237\u5185\u5b58 f<\/p>\n

        \u7ebf\u7a0b A<\/p>\n

        \u7ebf\u7a0b B<\/p>\n

        \u5185\u6838 futex<\/p>\n

        \u7528\u6237\u5185\u5b58 f<\/p>\n

        \u7ebf\u7a0b A<\/p>\n

        #mermaid-svg-mlIS5NiETSWFRIQA{font-family:\\”trebuchet ms\\”,verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#mermaid-svg-mlIS5NiETSWFRIQA .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#mermaid-svg-mlIS5NiETSWFRIQA .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#mermaid-svg-mlIS5NiETSWFRIQA .error-icon{fill:#552222;}#mermaid-svg-mlIS5NiETSWFRIQA .error-text{fill:#552222;stroke:#552222;}#mermaid-svg-mlIS5NiETSWFRIQA .edge-thickness-normal{stroke-width:1px;}#mermaid-svg-mlIS5NiETSWFRIQA .edge-thickness-thick{stroke-width:3.5px;}#mermaid-svg-mlIS5NiETSWFRIQA .edge-pattern-solid{stroke-dasharray:0;}#mermaid-svg-mlIS5NiETSWFRIQA .edge-thickness-invisible{stroke-width:0;fill:none;}#mermaid-svg-mlIS5NiETSWFRIQA .edge-pattern-dashed{stroke-dasharray:3;}#mermaid-svg-mlIS5NiETSWFRIQA .edge-pattern-dotted{stroke-dasharray:2;}#mermaid-svg-mlIS5NiETSWFRIQA .marker{fill:#333333;stroke:#333333;}#mermaid-svg-mlIS5NiETSWFRIQA .marker.cross{stroke:#333333;}#mermaid-svg-mlIS5NiETSWFRIQA svg{font-family:\\”trebuchet ms\\”,verdana,arial,sans-serif;font-size:16px;}#mermaid-svg-mlIS5NiETSWFRIQA p{margin:0;}#mermaid-svg-mlIS5NiETSWFRIQA .actor{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-mlIS5NiETSWFRIQA text.actor>tspan{fill:black;stroke:none;}#mermaid-svg-mlIS5NiETSWFRIQA .actor-line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);}#mermaid-svg-mlIS5NiETSWFRIQA .innerArc{stroke-width:1.5;stroke-dasharray:none;}#mermaid-svg-mlIS5NiETSWFRIQA .messageLine0{stroke-width:1.5;stroke-dasharray:none;stroke:#333;}#mermaid-svg-mlIS5NiETSWFRIQA .messageLine1{stroke-width:1.5;stroke-dasharray:2,2;stroke:#333;}#mermaid-svg-mlIS5NiETSWFRIQA #arrowhead path{fill:#333;stroke:#333;}#mermaid-svg-mlIS5NiETSWFRIQA .sequenceNumber{fill:white;}#mermaid-svg-mlIS5NiETSWFRIQA #sequencenumber{fill:#333;}#mermaid-svg-mlIS5NiETSWFRIQA #crosshead path{fill:#333;stroke:#333;}#mermaid-svg-mlIS5NiETSWFRIQA .messageText{fill:#333;stroke:none;}#mermaid-svg-mlIS5NiETSWFRIQA .labelBox{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-mlIS5NiETSWFRIQA .labelText,#mermaid-svg-mlIS5NiETSWFRIQA .labelText>tspan{fill:black;stroke:none;}#mermaid-svg-mlIS5NiETSWFRIQA .loopText,#mermaid-svg-mlIS5NiETSWFRIQA .loopText>tspan{fill:black;stroke:none;}#mermaid-svg-mlIS5NiETSWFRIQA .loopLine{stroke-width:2px;stroke-dasharray:2,2;stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);}#mermaid-svg-mlIS5NiETSWFRIQA .note{stroke:#aaaa33;fill:#fff5ad;}#mermaid-svg-mlIS5NiETSWFRIQA .noteText,#mermaid-svg-mlIS5NiETSWFRIQA .noteText>tspan{fill:black;stroke:none;}#mermaid-svg-mlIS5NiETSWFRIQA .activation0{fill:#f4f4f4;stroke:#666;}#mermaid-svg-mlIS5NiETSWFRIQA .activation1{fill:#f4f4f4;stroke:#666;}#mermaid-svg-mlIS5NiETSWFRIQA .activation2{fill:#f4f4f4;stroke:#666;}#mermaid-svg-mlIS5NiETSWFRIQA .actorPopupMenu{position:absolute;}#mermaid-svg-mlIS5NiETSWFRIQA .actorPopupMenuPanel{position:absolute;fill:#ECECFF;box-shadow:0px 8px 16px 0px rgba(0,0,0,0.2);filter:drop-shadow(3px 5px 2px rgb(0 0 0 \/ 0.4));}#mermaid-svg-mlIS5NiETSWFRIQA .actor-man line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-mlIS5NiETSWFRIQA .actor-man circle,#mermaid-svg-mlIS5NiETSWFRIQA line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;stroke-width:2px;}#mermaid-svg-mlIS5NiETSWFRIQA :root{–mermaid-font-family:\\”trebuchet ms\\”,verdana,arial,sans-serif;}<\/p>\n

        cmpxchg 0\u21921 \u6210\u529f<\/p>\n

        （\u65e0\u7cfb\u7edf\u8c03\u7528）<\/p>\n

        cmpxchg 0\u21921 \u5931\u8d25<\/p>\n

        xchg \u7f6e\u4e3a 2<\/p>\n

        futex_wait(f, 2)<\/p>\n

        \u68c0\u67e5 *f == 2<\/p>\n

        B \u5165\u961f\u5e76\u7761\u7720<\/p>\n

        atomic_dec：2\u21921<\/p>\n

        \u4e0d\u662f 1，\u8bf4\u660e\u6709\u7b49\u5f85\u8005<\/p>\n

        *f = 0<\/p>\n

        futex_wake(f, 1)<\/p>\n

        B \u56de\u5230\u8fd0\u884c\u961f\u5217<\/p>\n

        xchg \u7f6e\u4e3a 2，\u62ff\u5230\u9501<\/p>\n

        \u8fd9\u5f20\u56fe\u56de\u7b54：futex \u9501\u5728\u4ec0\u4e48\u65f6\u5019\u624d\u8fdb\u5185\u6838？<\/p>\n

        \u7ed3\u8bba：\u65e0\u7ade\u4e89\u65f6\u52a0\u9501\u548c\u89e3\u9501\u90fd\u4e0d\u8fdb\u5185\u6838；\u53ea\u6709"\u771f\u8981\u7761"\u548c"\u771f\u8981\u53eb\u9192\u4eba"\u624d\u6709\u7528\u6237\u6001\/\u5185\u6838\u6001\u5207\u6362\u3002 \u8fd9\u5c31\u662f"\u9501\u672c\u8eab\u4e0d\u8d35，\u7ade\u4e89\u624d\u8d35"\u7684\u7269\u7406\u539f\u56e0\u3002<\/p>\n

        1.6 \u6761\u4ef6\u53d8\u91cf：pthread_cond \u7684\u9aa8\u67b6<\/h4>\n

        \u6761\u4ef6\u53d8\u91cf\u7684\u96be\u70b9\u662f wait \u5fc5\u987b\u539f\u5b50\u5730"\u91ca\u653e\u4e92\u65a5\u9501 + \u7761\u4e0b"\u3002\u7528 futex \u53ef\u4ee5\u8fd9\u6837\u505a（\u7b80\u5316\u7248）：<\/p>\n

        void<\/span> cond_wait<\/span>(<\/span>cond_t<\/span> *<\/span>cv,<\/span> mutex_t<\/span> *<\/span>m)<\/span> {<\/span>
        \n int<\/span> seq =<\/span> cv-><\/span>seq;<\/span> \/\/ \u2460 \u8bb0\u4e0b\u5f53\u524d"\u4fe1\u53f7\u5e8f\u53f7"<\/span>
        \n mutex_unlock<\/span>(<\/span>m)<\/span>;<\/span> \/\/ \u2461 \u91ca\u653e\u4e92\u65a5\u9501<\/span>
        \n futex_wait<\/span>(<\/span>&<\/span>cv-><\/span>seq,<\/span> seq)<\/span>;<\/span> \/\/ \u2462 \u5e8f\u53f7\u6ca1\u53d8\u624d\u7761<\/span>
        \n mutex_lock<\/span>(<\/span>m)<\/span>;<\/span> \/\/ \u2463 \u9192\u6765\u540e\u91cd\u65b0\u62a2\u9501（Mesa）<\/span>
        \n}<\/span><\/p>\n

        void<\/span> cond_signal<\/span>(<\/span>cond_t<\/span> *<\/span>cv)<\/span> {<\/span>
        \n atomic_inc<\/span>(<\/span>&<\/span>cv-><\/span>seq)<\/span>;<\/span> \/\/ \u6539\u5e8f\u53f7<\/span>
        \n futex_wake<\/span>(<\/span>&<\/span>cv-><\/span>seq,<\/span> 1<\/span>)<\/span>;<\/span> \/\/ \u53eb\u9192\u4e00\u4e2a<\/span>
        \n}<\/span><\/p>\n

        \u5982\u679c signal \u6070\u597d\u53d1\u751f\u5728 \u2461 \u548c \u2462 \u4e4b\u95f4，\u5e8f\u53f7\u5df2\u7ecf\u53d8\u4e86，\u2462 \u7684 futex_wait \u4f1a\u7acb\u5373\u8fd4\u56de，\u4fe1\u53f7\u4e0d\u4f1a\u4e22\u3002\u2463 \u4f53\u73b0\u4e86 Mesa \u8bed\u4e49：\u9192\u6765\u7684\u7ebf\u7a0b\u8981\u91cd\u65b0\u7ade\u4e89\u4e92\u65a5\u9501，\u6240\u4ee5\u8c03\u7528\u65b9\u5fc5\u987b while (!cond) pthread_cond_wait(…)\u3002<\/p>\n

        \u771f\u5b9e\u7684 glibc \u5b9e\u73b0（2.25 \u8d77\u7684\u65b0\u7b97\u6cd5）\u6bd4\u8fd9\u590d\u6742\u5f97\u591a：\u5b83\u628a\u7b49\u5f85\u8005\u5206\u6210\u4e24\u7ec4\u6765\u4fdd\u8bc1 signal \u4e0d\u4f1a\u5524\u9192"\u6bd4\u5b83\u66f4\u665a\u5f00\u59cb\u7b49\u5f85"\u7684\u7ebf\u7a0b，\u8fd8\u8981\u5904\u7406\u5e8f\u53f7\u56de\u7ed5\u548c\u53d6\u6d88\u3002\u4f46\u9aa8\u67b6\u5c31\u662f\u4e0a\u9762\u8fd9\u56db\u6b65\u3002<\/p>\n

        \u7b2c\u4e8c\u90e8\u5206：Java \u7684\u7ba1\u7a0b\u662f\u600e\u4e48\u5b9e\u73b0\u7684<\/h3>\n

        Java \u8bed\u8a00\u5c42\u9762"\u6bcf\u4e2a\u5bf9\u8c61\u90fd\u662f\u7ba1\u7a0b"，\u4f46\u7269\u7406\u4e0a\u5e76\u4e0d\u662f\u6bcf\u4e2a\u5bf9\u8c61\u90fd\u5e26\u7740\u4e00\u4e2a\u7ba1\u7a0b\u2014\u2014\u90a3\u6837\u5185\u5b58\u5f00\u9500\u65e0\u6cd5\u627f\u53d7\u3002HotSpot \u7684\u505a\u6cd5\u662f：\u9501\u72b6\u6001\u5148\u6324\u5728\u5bf9\u8c61\u5934\u7684 64 \u4f4d\u91cc，\u53ea\u6709\u771f\u6b63\u9700\u8981\u6392\u961f\u65f6，\u624d\u5206\u914d\u4e00\u4e2a ObjectMonitor \u7ed3\u6784\u3002<\/p>\n

        2.1 \u5b57\u8282\u7801\u5165\u53e3：monitorenter \/ monitorexit<\/h4>\n

        synchronized \u4ee3\u7801\u5757\u7f16\u8bd1\u6210\u4e00\u5bf9\u5b57\u8282\u7801 monitorenter \/ monitorexit，\u7f16\u8bd1\u5668\u8fd8\u4f1a\u989d\u5916\u751f\u6210\u4e00\u4e2a\u5f02\u5e38\u5904\u7406\u5668，\u4fdd\u8bc1\u629b\u5f02\u5e38\u65f6\u4e5f\u6267\u884c monitorexit\u2014\u2014\u8fd9\u5c31\u662f"\u7f16\u8bd1\u5668\u66ff\u4f60\u91ca\u653e\u9501"\u7684\u5b9e\u73b0\u3002synchronized \u65b9\u6cd5\u4e0d\u751f\u6210\u8fd9\u4e24\u6761\u5b57\u8282\u7801，\u800c\u662f\u5728\u65b9\u6cd5\u6807\u5fd7\u4e0a\u7f6e ACC_SYNCHRONIZED，\u7531 JVM \u5728\u8c03\u7528\u548c\u8fd4\u56de\u65f6\u52a0\u89e3\u9501\u3002\u7ba1\u7a0b\u7406\u8bba\u91cc"\u52a0\u9501\u7531\u7f16\u8bd1\u5668\u63d2\u5165，\u7a0b\u5e8f\u5458\u5fd8\u4e0d\u4e86"，\u5728\u8fd9\u91cc\u4e00\u5b57\u4e0d\u5dee\u5730\u843d\u5730\u4e86\u3002<\/p>\n

        2.2 \u5bf9\u8c61\u5934\u7684 Mark Word<\/h4>\n

        64 \u4f4d HotSpot \u4e2d，\u6bcf\u4e2a\u5bf9\u8c61\u5934\u7684\u7b2c\u4e00\u4e2a\u5b57\u662f Mark Word\u3002\u5b83\u7684\u6700\u4f4e 2 \u4f4d（\u52a0\u4e0a\u66fe\u7ecf\u7684 1 \u4f4d\u504f\u5411\u6807\u5fd7）\u51b3\u5b9a\u5176\u4f59\u4f4d\u7684\u542b\u4e49\u3002\u4e0b\u8868\u662f\u672a\u5f00\u542f\u7d27\u51d1\u5bf9\u8c61\u5934\u65f6\u7684\u7ecf\u5178\u5e03\u5c40：<\/p>\n\n\u9501\u72b6\u6001\u9ad8\u4f4d\u5185\u5bb9\u504f\u5411\u4f4d\u9501\u6807\u5fd7（\u6700\u4f4e 2 \u4f4d）<\/tr>\n\n\n\n\n\n\n
        \u65e0\u9501<\/td>\n25 \u4f4d\u672a\u7528 \u00b7 31 \u4f4d identity hash \u00b7 1 \u4f4d\u672a\u7528 \u00b7 4 \u4f4d GC \u5e74\u9f84<\/td>\n0<\/td>\n01<\/td>\n<\/tr>\n
        \u504f\u5411\u9501（\u5df2\u79fb\u9664）<\/td>\n54 \u4f4d\u6301\u6709\u7ebf\u7a0b\u6307\u9488 \u00b7 2 \u4f4d epoch \u00b7 1 \u4f4d\u672a\u7528 \u00b7 4 \u4f4d GC \u5e74\u9f84<\/td>\n1<\/td>\n01<\/td>\n<\/tr>\n
        \u8f7b\u91cf\u7ea7\u9501（\u65e7\u5b9e\u73b0）<\/td>\n62 \u4f4d：\u6307\u5411\u6808\u4e0a\u9501\u8bb0\u5f55\u7684\u6307\u9488<\/td>\n\u2014<\/td>\n00<\/td>\n<\/tr>\n
        \u91cd\u91cf\u7ea7\u9501<\/td>\n62 \u4f4d：\u6307\u5411 ObjectMonitor \u7684\u6307\u9488<\/td>\n\u2014<\/td>\n10<\/td>\n<\/tr>\n
        GC \u6807\u8bb0<\/td>\nGC \u4f7f\u7528<\/td>\n\u2014<\/td>\n11<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

        \u4e24\u70b9\u8981\u6ce8\u610f：<\/p>\n

          \n
        • \u4e00\u4e2a\u5b57\u88ab\u53cd\u590d\u590d\u7528，\u610f\u5473\u7740 identity hash\u3001GC \u5e74\u9f84\u8fd9\u4e9b\u4fe1\u606f\u5728\u52a0\u9501\u65f6\u4f1a\u88ab"\u6324\u8d70"，\u5fc5\u987b\u53e6\u627e\u5730\u65b9\u6682\u5b58（\u65e7\u8f7b\u91cf\u7ea7\u9501\u5b58\u5230\u6808\u4e0a\u7684"displaced header"，\u91cd\u91cf\u7ea7\u9501\u5b58\u5230 ObjectMonitor \u91cc）\u3002<\/li>\n
        • \u7d27\u51d1\u5bf9\u8c61\u5934（JEP 450 \u5728 JDK 24 \u5b9e\u9a8c\u6027\u5f15\u5165，JEP 519 \u5728 JDK 25 \u8f6c\u6b63）\u628a\u5bf9\u8c61\u5934\u538b\u7f29\u5230 64 \u4f4d，\u5e03\u5c40\u968f\u4e4b\u6539\u53d8；\u5b83\u8981\u6c42\u914d\u5408\u4e0b\u9762\u63d0\u5230\u7684\u65b0\u8f7b\u91cf\u7ea7\u9501\u548c"ObjectMonitor \u8868"\u3002\u4e0a\u8868\u662f\u7406\u89e3\u539f\u7406\u7528\u7684\u7ecf\u5178\u7248\u672c\u3002<\/li>\n<\/ul>\n

          2.3 \u9501\u7684\u51e0\u79cd\u72b6\u6001\u4e0e\u5347\u7ea7\u8def\u5f84<\/h4>\n

          #mermaid-svg-mt1GFpg6iytSrpMw{font-family:\\”trebuchet ms\\”,verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#mermaid-svg-mt1GFpg6iytSrpMw .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#mermaid-svg-mt1GFpg6iytSrpMw .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#mermaid-svg-mt1GFpg6iytSrpMw .error-icon{fill:#552222;}#mermaid-svg-mt1GFpg6iytSrpMw .error-text{fill:#552222;stroke:#552222;}#mermaid-svg-mt1GFpg6iytSrpMw .edge-thickness-normal{stroke-width:1px;}#mermaid-svg-mt1GFpg6iytSrpMw .edge-thickness-thick{stroke-width:3.5px;}#mermaid-svg-mt1GFpg6iytSrpMw .edge-pattern-solid{stroke-dasharray:0;}#mermaid-svg-mt1GFpg6iytSrpMw .edge-thickness-invisible{stroke-width:0;fill:none;}#mermaid-svg-mt1GFpg6iytSrpMw .edge-pattern-dashed{stroke-dasharray:3;}#mermaid-svg-mt1GFpg6iytSrpMw .edge-pattern-dotted{stroke-dasharray:2;}#mermaid-svg-mt1GFpg6iytSrpMw .marker{fill:#333333;stroke:#333333;}#mermaid-svg-mt1GFpg6iytSrpMw .marker.cross{stroke:#333333;}#mermaid-svg-mt1GFpg6iytSrpMw svg{font-family:\\”trebuchet ms\\”,verdana,arial,sans-serif;font-size:16px;}#mermaid-svg-mt1GFpg6iytSrpMw p{margin:0;}#mermaid-svg-mt1GFpg6iytSrpMw defs #statediagram-barbEnd{fill:#333333;stroke:#333333;}#mermaid-svg-mt1GFpg6iytSrpMw g.stateGroup text{fill:#9370DB;stroke:none;font-size:10px;}#mermaid-svg-mt1GFpg6iytSrpMw g.stateGroup text{fill:#333;stroke:none;font-size:10px;}#mermaid-svg-mt1GFpg6iytSrpMw g.stateGroup .state-title{font-weight:bolder;fill:#131300;}#mermaid-svg-mt1GFpg6iytSrpMw g.stateGroup rect{fill:#ECECFF;stroke:#9370DB;}#mermaid-svg-mt1GFpg6iytSrpMw g.stateGroup line{stroke:#333333;stroke-width:1;}#mermaid-svg-mt1GFpg6iytSrpMw .transition{stroke:#333333;stroke-width:1;fill:none;}#mermaid-svg-mt1GFpg6iytSrpMw .stateGroup .composit{fill:white;border-bottom:1px;}#mermaid-svg-mt1GFpg6iytSrpMw .stateGroup .alt-composit{fill:#e0e0e0;border-bottom:1px;}#mermaid-svg-mt1GFpg6iytSrpMw .state-note{stroke:#aaaa33;fill:#fff5ad;}#mermaid-svg-mt1GFpg6iytSrpMw .state-note text{fill:black;stroke:none;font-size:10px;}#mermaid-svg-mt1GFpg6iytSrpMw .stateLabel .box{stroke:none;stroke-width:0;fill:#ECECFF;opacity:0.5;}#mermaid-svg-mt1GFpg6iytSrpMw .edgeLabel .label rect{fill:#ECECFF;opacity:0.5;}#mermaid-svg-mt1GFpg6iytSrpMw .edgeLabel{background-color:rgba(232,232,232, 0.8);text-align:center;}#mermaid-svg-mt1GFpg6iytSrpMw .edgeLabel p{background-color:rgba(232,232,232, 0.8);}#mermaid-svg-mt1GFpg6iytSrpMw .edgeLabel rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#mermaid-svg-mt1GFpg6iytSrpMw .edgeLabel .label text{fill:#333;}#mermaid-svg-mt1GFpg6iytSrpMw .label div .edgeLabel{color:#333;}#mermaid-svg-mt1GFpg6iytSrpMw .stateLabel text{fill:#131300;font-size:10px;font-weight:bold;}#mermaid-svg-mt1GFpg6iytSrpMw .node circle.state-start{fill:#333333;stroke:#333333;}#mermaid-svg-mt1GFpg6iytSrpMw .node .fork-join{fill:#333333;stroke:#333333;}#mermaid-svg-mt1GFpg6iytSrpMw .node circle.state-end{fill:#9370DB;stroke:white;stroke-width:1.5;}#mermaid-svg-mt1GFpg6iytSrpMw .end-state-inner{fill:white;stroke-width:1.5;}#mermaid-svg-mt1GFpg6iytSrpMw .node rect{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#mermaid-svg-mt1GFpg6iytSrpMw .node polygon{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#mermaid-svg-mt1GFpg6iytSrpMw #statediagram-barbEnd{fill:#333333;}#mermaid-svg-mt1GFpg6iytSrpMw .statediagram-cluster rect{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#mermaid-svg-mt1GFpg6iytSrpMw .cluster-label,#mermaid-svg-mt1GFpg6iytSrpMw .nodeLabel{color:#131300;}#mermaid-svg-mt1GFpg6iytSrpMw .statediagram-cluster rect.outer{rx:5px;ry:5px;}#mermaid-svg-mt1GFpg6iytSrpMw .statediagram-state .divider{stroke:#9370DB;}#mermaid-svg-mt1GFpg6iytSrpMw .statediagram-state .title-state{rx:5px;ry:5px;}#mermaid-svg-mt1GFpg6iytSrpMw .statediagram-cluster.statediagram-cluster .inner{fill:white;}#mermaid-svg-mt1GFpg6iytSrpMw .statediagram-cluster.statediagram-cluster-alt .inner{fill:#f0f0f0;}#mermaid-svg-mt1GFpg6iytSrpMw .statediagram-cluster .inner{rx:0;ry:0;}#mermaid-svg-mt1GFpg6iytSrpMw .statediagram-state rect.basic{rx:5px;ry:5px;}#mermaid-svg-mt1GFpg6iytSrpMw .statediagram-state rect.divider{stroke-dasharray:10,10;fill:#f0f0f0;}#mermaid-svg-mt1GFpg6iytSrpMw .note-edge{stroke-dasharray:5;}#mermaid-svg-mt1GFpg6iytSrpMw .statediagram-note rect{fill:#fff5ad;stroke:#aaaa33;stroke-width:1px;rx:0;ry:0;}#mermaid-svg-mt1GFpg6iytSrpMw .statediagram-note rect{fill:#fff5ad;stroke:#aaaa33;stroke-width:1px;rx:0;ry:0;}#mermaid-svg-mt1GFpg6iytSrpMw .statediagram-note text{fill:black;}#mermaid-svg-mt1GFpg6iytSrpMw .statediagram-note .nodeLabel{color:black;}#mermaid-svg-mt1GFpg6iytSrpMw .statediagram .edgeLabel{color:red;}#mermaid-svg-mt1GFpg6iytSrpMw #dependencyStart,#mermaid-svg-mt1GFpg6iytSrpMw #dependencyEnd{fill:#333333;stroke:#333333;stroke-width:1;}#mermaid-svg-mt1GFpg6iytSrpMw .statediagramTitleText{text-anchor:middle;font-size:18px;fill:#333;}#mermaid-svg-mt1GFpg6iytSrpMw :root{–mermaid-font-family:\\”trebuchet ms\\”,verdana,arial,sans-serif;}<\/p>\n

          <\/span><\/p>\n

          <\/p>\n

          CAS \u6539\u9501\u4f4d\u6210\u529f<\/p>\n

          <\/span><\/p>\n

          <\/p>\n

          \u9000\u51fa\u65f6 CAS \u8fd8\u539f<\/p>\n

          <\/span><\/p>\n

          <\/p>\n

          \u51fa\u73b0\u7ade\u4e89\u6216\u8c03\u7528 wait()<\/p>\n

          <\/span><\/p>\n

          <\/p>\n

          \u76f4\u63a5\u7ade\u4e89\u6216\u8c03\u7528 wait()<\/p>\n

          <\/span><\/p>\n

          <\/p>\n

          \u7a7a\u95f2\u540e\u88ab\u5f02\u6b65\u6536\u7f29（deflation）<\/p>\n

          <\/span><\/p>\n

          <\/p>\n

          \u65e0\u9501<\/p>\n

          <\/span><\/p>\n

          <\/p>\n

          \u8f7b\u91cf\u7ea7\u9501<\/p>\n

          <\/span><\/p>\n

          <\/p>\n

          \u91cd\u91cf\u7ea7\u9501<\/p>\n

          <\/span><\/p>\n

          \u8fd9\u5f20\u56fe\u56de\u7b54：\u4e00\u4e2a\u5bf9\u8c61\u7684\u9501\u72b6\u6001\u5982\u4f55\u5728\u65e0\u9501\u3001\u8f7b\u91cf\u7ea7\u3001\u91cd\u91cf\u7ea7\u4e4b\u95f4\u8fc1\u79fb？（\u504f\u5411\u9501\u5df2\u79fb\u9664，\u672a\u753b\u51fa）<\/p>\n

          \u504f\u5411\u9501（\u5386\u53f2）\u3002 \u89c2\u5bdf\u4f9d\u636e\u662f：\u5927\u591a\u6570\u9501\u4ece\u5934\u5230\u5c3e\u53ea\u88ab\u4e00\u4e2a\u7ebf\u7a0b\u7528\u3002\u7b2c\u4e00\u6b21\u52a0\u9501\u65f6\u7528\u4e00\u6b21 CAS \u628a\u7ebf\u7a0b ID \u5199\u8fdb Mark Word，\u4ee5\u540e\u540c\u4e00\u7ebf\u7a0b\u518d\u8fdb\u5165，\u53ea\u9700\u6bd4\u8f83\u7ebf\u7a0b ID，\u8fde CAS \u90fd\u4e0d\u7528\u3002\u4ee3\u4ef7\u5728\u64a4\u9500：\u53e6\u4e00\u4e2a\u7ebf\u7a0b\u6765\u62a2\u65f6，\u5fc5\u987b\u5728\u5b89\u5168\u70b9（safepoint）\u6682\u505c\u6301\u6709\u8005，\u68c0\u67e5\u5b83\u7684\u6808\u6765\u5224\u65ad\u662f\u5426\u8fd8\u6301\u6709\u9501\u3002\u968f\u7740\u73b0\u4ee3 CPU \u4e0a\u65e0\u7ade\u4e89 CAS \u8d8a\u6765\u8d8a\u4fbf\u5b9c，\u800c\u64a4\u9500\u53c8\u8d35\u3001\u4ee3\u7801\u53c8\u590d\u6742，\u504f\u5411\u9501\u5728 JDK 15 \u88ab\u9ed8\u8ba4\u5173\u95ed\u5e76\u5e9f\u5f03（JEP 374），JDK 18 \u4e2d\u76f8\u5173\u53c2\u6570\u88ab\u6dd8\u6c70\u3001\u5b9e\u73b0\u88ab\u79fb\u9664\u3002\u4eca\u5929\u8bb2"\u504f\u5411 \u2192 \u8f7b\u91cf \u2192 \u91cd\u91cf"\u4e09\u6bb5\u5347\u7ea7，\u662f\u5728\u8bb2 JDK 15 \u4e4b\u524d\u7684\u9ed8\u8ba4\u884c\u4e3a\u3002<\/p>\n

          \u8f7b\u91cf\u7ea7\u9501（\u65e7\u5b9e\u73b0，\u201c\u6808\u9501\u201d）\u3002 \u7ebf\u7a0b\u5728\u5f53\u524d\u6808\u5e27\u91cc\u5206\u914d\u4e00\u4e2a\u9501\u8bb0\u5f55（lock record），\u628a\u5bf9\u8c61\u539f\u6765\u7684 Mark Word \u590d\u5236\u8fdb\u53bb（displaced header），\u7136\u540e CAS \u628a Mark Word \u6539\u6210\u6307\u5411\u8fd9\u4e2a\u9501\u8bb0\u5f55\u7684\u6307\u9488\u3001\u9501\u4f4d 00\u3002\u91cd\u5165\u65f6\u518d\u538b\u4e00\u4e2a displaced header \u4e3a\u7a7a\u7684\u9501\u8bb0\u5f55\u5373\u53ef\u3002\u89e3\u9501\u65f6 CAS \u628a displaced header \u6362\u56de\u53bb\u3002\u5168\u7a0b\u53ea\u6709\u7528\u6237\u6001 CAS，\u6ca1\u6709\u7cfb\u7edf\u8c03\u7528\u3002<\/p>\n

          \u8f7b\u91cf\u7ea7\u9501（\u65b0\u5b9e\u73b0，lock-stack）\u3002 JDK 21 \u5f15\u5165\u3001JDK 23 \u8d77\u6210\u4e3a\u9ed8\u8ba4（LockingMode \u9ed8\u8ba4\u503c\u6539\u4e3a lightweight）\u3002\u6bcf\u4e2a\u7ebf\u7a0b\u6709\u4e00\u4e2a\u5c0f\u6570\u7ec4"\u9501\u6808"（lock-stack），\u52a0\u9501\u65f6 CAS \u53ea\u628a Mark Word \u7684\u9501\u4f4d\u4ece 01 \u6539\u6210 00，\u5e76\u628a\u5bf9\u8c61\u5f15\u7528\u538b\u8fdb\u81ea\u5df1\u7684\u9501\u6808；Mark Word \u7684\u5176\u4f59\u4f4d（hash\u3001\u5e74\u9f84）\u539f\u6837\u4fdd\u7559，\u4e0d\u518d\u6709\u6307\u5411\u6808\u7684\u6307\u9488\u3002\u5224\u65ad"\u662f\u4e0d\u662f\u6211\u6301\u6709"\u53ea\u9700\u67e5\u81ea\u5df1\u7684\u9501\u6808\u3002\u8fd9\u6837\u505a\u7684\u52a8\u673a\u4e4b\u4e00，\u662f\u7ed9\u7d27\u51d1\u5bf9\u8c61\u5934\u548c\u865a\u62df\u7ebf\u7a0b\u8ba9\u8def\u2014\u2014\u6307\u5411\u67d0\u4e2a\u7ebf\u7a0b\u6808\u7684\u6307\u9488\u5728\u8fd9\u4e24\u79cd\u573a\u666f\u4e0b\u90fd\u5f88\u788d\u4e8b\u3002<\/p>\n

          \u81a8\u80c0\u4e3a\u91cd\u91cf\u7ea7\u9501\u3002 \u4ee5\u4e0b\u60c5\u51b5\u4f1a\u89e6\u53d1 inflate：<\/p>\n

            \n
          • \u8f7b\u91cf\u7ea7\u52a0\u9501\u7684 CAS \u5931\u8d25（\u6709\u7ade\u4e89）；<\/li>\n
          • \u6301\u9501\u7ebf\u7a0b\u8c03\u7528\u4e86 wait()\u2014\u2014\u8f7b\u91cf\u7ea7\u9501\u6ca1\u6709 wait set，\u5fc5\u987b\u6709 ObjectMonitor；<\/li>\n
          • \u9501\u6808\u6ee1\u4e86，\u6216\u5176\u4ed6\u5b9e\u73b0\u4e0a\u7684\u9650\u5236\u3002<\/li>\n<\/ul>\n

            \u81a8\u80c0\u65f6\u5206\u914d（\u6216\u4ece\u7f13\u5b58\u53d6\u51fa）\u4e00\u4e2a ObjectMonitor，\u628a Mark Word \u6539\u4e3a\u6307\u5411\u5b83\u3001\u9501\u4f4d 10\u3002JDK 24 \u8d77\u8fd8\u53ef\u4ee5\u7528 -XX:+UseObjectMonitorTable \u628a"\u5bf9\u8c61 \u2192 \u76d1\u89c6\u5668"\u7684\u6620\u5c04\u653e\u8fdb\u4e00\u5f20\u65c1\u8def\u54c8\u5e0c\u8868，\u4e0d\u518d\u6539\u5199 Mark Word（\u7d27\u51d1\u5bf9\u8c61\u5934\u9700\u8981\u8fd9\u4e2a\u80fd\u529b）\u3002<\/p>\n

            \u9501\u4f1a\u964d\u7ea7\u5417？ \u5e38\u89c1\u8bf4\u6cd5\u662f"\u9501\u53ea\u80fd\u5347\u7ea7\u4e0d\u80fd\u964d\u7ea7"\u3002\u5bf9\u5355\u6b21\u6301\u6709\u8fc7\u7a0b\u6765\u8bf4\u5927\u4f53\u5982\u6b64，\u4f46 ObjectMonitor \u5e76\u4e0d\u6c38\u4e45\u7ed1\u5b9a\u5728\u5bf9\u8c61\u4e0a：JDK 15 \u8d77\u6709\u4e13\u95e8\u7684\u7ebf\u7a0b**\u5f02\u6b65\u6536\u7f29（deflate）**\u7a7a\u95f2\u7684\u76d1\u89c6\u5668，\u628a\u5bf9\u8c61\u6062\u590d\u4e3a\u65e0\u9501\u72b6\u6001，\u76d1\u89c6\u5668\u56de\u6536\u590d\u7528\u3002\u6240\u4ee5\u66f4\u51c6\u786e\u7684\u8bf4\u6cd5\u662f：\u5728\u6301\u6709\u671f\u95f4\u4e0d\u964d\u7ea7，\u7a7a\u95f2\u540e\u4f1a\u88ab\u6536\u7f29\u3002<\/p>\n

            2.4 ObjectMonitor：\u7ba1\u7a0b\u7684\u5b8c\u6574\u5f62\u6001<\/h4>\n

            ObjectMonitor \u662f C++ \u5bf9\u8c61，\u5c31\u662f\u6559\u79d1\u4e66\u7ba1\u7a0b\u5728 HotSpot \u91cc\u7684\u5b9e\u4f53\u3002\u7ecf\u5178\u7248\u672c（JDK 8\u201321 \u4e00\u5e26）\u7684\u5173\u952e\u5b57\u6bb5：<\/p>\n\n\u5b57\u6bb5\u4f5c\u7528\u5bf9\u5e94\u7ba1\u7a0b\u6982\u5ff5<\/tr>\n\n\n\n\n\n\n\n
            _owner<\/td>\n\u5f53\u524d\u6301\u6709\u8005<\/td>\n\u7ba1\u7a0b\u5185\u7684\u90a3\u4e2a\u7ebf\u7a0b<\/td>\n<\/tr>\n
            _recursions<\/td>\n\u91cd\u5165\u6b21\u6570<\/td>\n\u53ef\u91cd\u5165<\/td>\n<\/tr>\n
            _cxq<\/td>\n\u65b0\u6765\u7ade\u4e89\u8005\u7684\u5355\u94fe\u8868，CAS \u5934\u63d2（LIFO）<\/td>\n\u5165\u53e3\u961f\u5217（\u65e0\u9501\u5165\u961f\u90e8\u5206）<\/td>\n<\/tr>\n
            _EntryList<\/td>\n\u89e3\u9501\u8005\u4ece\u4e2d\u6311\u9009\u7ee7\u4efb\u8005\u7684\u53cc\u5411\u94fe\u8868<\/td>\n\u5165\u53e3\u961f\u5217<\/td>\n<\/tr>\n
            _WaitSet<\/td>\n\u8c03\u7528\u4e86 wait() \u7684\u7ebf\u7a0b\u7684\u73af\u5f62\u53cc\u5411\u94fe\u8868<\/td>\n\u6761\u4ef6\u53d8\u91cf\u7684\u7b49\u5f85\u961f\u5217<\/td>\n<\/tr>\n
            _succ<\/td>\n\u5df2\u88ab\u9009\u4e3a"\u5047\u5b9a\u7ee7\u4efb\u8005"\u7684\u7ebf\u7a0b<\/td>\n\u907f\u514d\u91cd\u590d\u5524\u9192<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

            \u8f83\u65b0\u7684 JDK \u5bf9\u8fd9\u4e9b\u7ed3\u6784\u505a\u8fc7\u91cd\u6784（\u4f8b\u5982\u4e3a JEP 491 \u8ba9 owner \u6539\u4e3a\u8bb0\u5f55\u7ebf\u7a0b ID \u4ee5\u652f\u6301\u865a\u62df\u7ebf\u7a0b，\u5165\u53e3\u961f\u5217\u4e5f\u6709\u5408\u5e76），\u5b57\u6bb5\u540d\u53ef\u80fd\u4e0d\u540c，\u4f46"owner + \u91cd\u5165\u8ba1\u6570 + \u5165\u53e3\u961f\u5217 + \u7b49\u5f85\u96c6\u5408"\u8fd9\u4e2a\u7ed3\u6784\u6ca1\u6709\u53d8\u3002<\/p>\n

            \u52a0\u9501（enter）\u7684\u8def\u5f84，\u53c8\u662f\u719f\u6089\u7684\u4e09\u6bb5\u5f0f：<\/p>\n

          • CAS \u62a2 owner：_owner \u4ece\u7a7a\u6539\u6210\u81ea\u5df1，\u6210\u529f\u5373\u8fd4\u56de；\u5982\u679c owner \u5df2\u7ecf\u662f\u81ea\u5df1，_recursions++\u3002<\/li>\n
          • \u81ea\u9002\u5e94\u81ea\u65cb：\u6839\u636e\u8fd9\u628a\u9501\u8fc7\u53bb\u81ea\u65cb\u6210\u529f\u7684\u5386\u53f2\u51b3\u5b9a\u8f6c\u591a\u4e45，\u8d4c\u6301\u6709\u8005\u9a6c\u4e0a\u91ca\u653e\u3002<\/li>\n
          • \u6392\u961f\u7761\u7720：\u628a\u81ea\u5df1\u5305\u88c5\u6210 ObjectWaiter \u8282\u70b9，CAS \u5934\u63d2\u8fdb _cxq，\u7136\u540e\u5faa\u73af"\u518d\u8bd5\u4e00\u6b21 \u2192 \u4e0d\u884c\u5c31 park"\u3002<\/li>\n

            \u89e3\u9501（exit）： _recursions \u4e0d\u4e3a 0 \u5c31\u51cf\u4e00\u8fd4\u56de；\u5426\u5219\u91ca\u653e owner（\u5e26\u5185\u5b58\u5c4f\u969c）\u3002\u5982\u679c\u6ca1\u6709\u7b49\u5f85\u8005，\u76f4\u63a5\u8fd4\u56de\u2014\u2014\u8fd9\u6761\u8def\u5f84\u4e0a\u4e5f\u6ca1\u6709\u7cfb\u7edf\u8c03\u7528\u3002\u5982\u679c\u6709\u7b49\u5f85\u8005，\u4ece _EntryList \u6311\u4e00\u4e2a\u7ee7\u4efb\u8005（_EntryList \u7a7a\u5c31\u5148\u628a _cxq \u6574\u4f53\u642c\u8fc7\u6765），\u53ea unpark \u8fd9\u4e00\u4e2a，\u907f\u514d\u60ca\u7fa4\u3002<\/p>\n

            \u6ce8\u610f\u7b2c 3 \u6b65\u9192\u6765\u540e\u662f"\u518d\u8bd5\u4e00\u6b21 CAS"，\u800c\u4e0d\u662f\u76f4\u63a5\u62ff\u5230\u9501：\u89e3\u9501\u8005\u53ea\u662f\u628a\u7ee7\u4efb\u8005\u53eb\u9192，\u9501\u672c\u8eab\u662f\u7a7a\u51fa\u6765\u8ba9\u5927\u5bb6\u62a2\u7684\u3002\u65b0\u6765\u7684\u7ebf\u7a0b\u53ef\u80fd\u5728\u7ee7\u4efb\u8005\u9192\u6765\u4e4b\u524d\u5c31 CAS \u6210\u529f（\u63d2\u961f，barging）\u3002\u8fd9\u8ba9 synchronized \u541e\u5410\u66f4\u9ad8，\u4f46\u5b83\u4e0d\u662f\u516c\u5e73\u9501\u2014\u2014\u60f3\u8981 FIFO，\u53ea\u80fd\u7528 new ReentrantLock(true)\u3002<\/p>\n

            2.5 wait \/ notify \u5728 ObjectMonitor \u91cc\u600e\u4e48\u8d70<\/h4>\n

            \u7ebf\u7a0b T2<\/p>\n

            ObjectMonitor<\/p>\n

            \u7ebf\u7a0b T1<\/p>\n

            \u7ebf\u7a0b T2<\/p>\n

            ObjectMonitor<\/p>\n

            \u7ebf\u7a0b T1<\/p>\n

            #mermaid-svg-vTbmYb9u5JBrKsOr{font-family:\\”trebuchet ms\\”,verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#mermaid-svg-vTbmYb9u5JBrKsOr .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#mermaid-svg-vTbmYb9u5JBrKsOr .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#mermaid-svg-vTbmYb9u5JBrKsOr .error-icon{fill:#552222;}#mermaid-svg-vTbmYb9u5JBrKsOr .error-text{fill:#552222;stroke:#552222;}#mermaid-svg-vTbmYb9u5JBrKsOr .edge-thickness-normal{stroke-width:1px;}#mermaid-svg-vTbmYb9u5JBrKsOr .edge-thickness-thick{stroke-width:3.5px;}#mermaid-svg-vTbmYb9u5JBrKsOr .edge-pattern-solid{stroke-dasharray:0;}#mermaid-svg-vTbmYb9u5JBrKsOr .edge-thickness-invisible{stroke-width:0;fill:none;}#mermaid-svg-vTbmYb9u5JBrKsOr .edge-pattern-dashed{stroke-dasharray:3;}#mermaid-svg-vTbmYb9u5JBrKsOr .edge-pattern-dotted{stroke-dasharray:2;}#mermaid-svg-vTbmYb9u5JBrKsOr .marker{fill:#333333;stroke:#333333;}#mermaid-svg-vTbmYb9u5JBrKsOr .marker.cross{stroke:#333333;}#mermaid-svg-vTbmYb9u5JBrKsOr svg{font-family:\\”trebuchet ms\\”,verdana,arial,sans-serif;font-size:16px;}#mermaid-svg-vTbmYb9u5JBrKsOr p{margin:0;}#mermaid-svg-vTbmYb9u5JBrKsOr .actor{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-vTbmYb9u5JBrKsOr text.actor>tspan{fill:black;stroke:none;}#mermaid-svg-vTbmYb9u5JBrKsOr .actor-line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);}#mermaid-svg-vTbmYb9u5JBrKsOr .innerArc{stroke-width:1.5;stroke-dasharray:none;}#mermaid-svg-vTbmYb9u5JBrKsOr .messageLine0{stroke-width:1.5;stroke-dasharray:none;stroke:#333;}#mermaid-svg-vTbmYb9u5JBrKsOr .messageLine1{stroke-width:1.5;stroke-dasharray:2,2;stroke:#333;}#mermaid-svg-vTbmYb9u5JBrKsOr #arrowhead path{fill:#333;stroke:#333;}#mermaid-svg-vTbmYb9u5JBrKsOr .sequenceNumber{fill:white;}#mermaid-svg-vTbmYb9u5JBrKsOr #sequencenumber{fill:#333;}#mermaid-svg-vTbmYb9u5JBrKsOr #crosshead path{fill:#333;stroke:#333;}#mermaid-svg-vTbmYb9u5JBrKsOr .messageText{fill:#333;stroke:none;}#mermaid-svg-vTbmYb9u5JBrKsOr .labelBox{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-vTbmYb9u5JBrKsOr .labelText,#mermaid-svg-vTbmYb9u5JBrKsOr .labelText>tspan{fill:black;stroke:none;}#mermaid-svg-vTbmYb9u5JBrKsOr .loopText,#mermaid-svg-vTbmYb9u5JBrKsOr .loopText>tspan{fill:black;stroke:none;}#mermaid-svg-vTbmYb9u5JBrKsOr .loopLine{stroke-width:2px;stroke-dasharray:2,2;stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);}#mermaid-svg-vTbmYb9u5JBrKsOr .note{stroke:#aaaa33;fill:#fff5ad;}#mermaid-svg-vTbmYb9u5JBrKsOr .noteText,#mermaid-svg-vTbmYb9u5JBrKsOr .noteText>tspan{fill:black;stroke:none;}#mermaid-svg-vTbmYb9u5JBrKsOr .activation0{fill:#f4f4f4;stroke:#666;}#mermaid-svg-vTbmYb9u5JBrKsOr .activation1{fill:#f4f4f4;stroke:#666;}#mermaid-svg-vTbmYb9u5JBrKsOr .activation2{fill:#f4f4f4;stroke:#666;}#mermaid-svg-vTbmYb9u5JBrKsOr .actorPopupMenu{position:absolute;}#mermaid-svg-vTbmYb9u5JBrKsOr .actorPopupMenuPanel{position:absolute;fill:#ECECFF;box-shadow:0px 8px 16px 0px rgba(0,0,0,0.2);filter:drop-shadow(3px 5px 2px rgb(0 0 0 \/ 0.4));}#mermaid-svg-vTbmYb9u5JBrKsOr .actor-man line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-vTbmYb9u5JBrKsOr .actor-man circle,#mermaid-svg-vTbmYb9u5JBrKsOr line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;stroke-width:2px;}#mermaid-svg-vTbmYb9u5JBrKsOr :root{–mermaid-font-family:\\”trebuchet ms\\”,verdana,arial,sans-serif;}<\/p>\n

            \u6301\u6709\u9501，\u8c03\u7528 wait()<\/p>\n

            T1 \u5165 _WaitSet<\/p>\n

            \u4fdd\u5b58\u91cd\u5165\u6b21\u6570，\u5f7b\u5e95\u91ca\u653e\u9501<\/p>\n

            park，\u7761\u7720<\/p>\n

            \u62a2\u5230\u9501，\u4fee\u6539\u72b6\u6001<\/p>\n

            notify()<\/p>\n

            T1 \u4ece _WaitSet<\/p>\n

            \u79fb\u5230\u5165\u53e3\u961f\u5217（\u5c1a\u672a\u5524\u9192）<\/p>\n

            \u9000\u51fa synchronized，\u91ca\u653e\u9501<\/p>\n

            \u9009\u4e2d T1 \u4e3a\u7ee7\u4efb\u8005<\/p>\n

            unpark<\/p>\n

            \u91cd\u65b0\u7ade\u4e89\u9501<\/p>\n

            \u6062\u590d\u91cd\u5165\u6b21\u6570<\/p>\n

            while \u91cd\u67e5\u6761\u4ef6<\/p>\n

            \u8fd9\u5f20\u56fe\u56de\u7b54：\u4e00\u6b21 wait\/notify，\u7ebf\u7a0b\u5728 ObjectMonitor \u7684\u54ea\u4e9b\u961f\u5217\u4e4b\u95f4\u79fb\u52a8，\u4f55\u65f6\u771f\u6b63\u88ab\u5524\u9192？<\/p>\n

            \u51e0\u4e2a\u4ece\u5b9e\u73b0\u91cc\u76f4\u63a5\u8bfb\u51fa\u6765\u7684\u4e8b\u5b9e：<\/p>\n

              \n
            • wait() \u5fc5\u987b\u5148\u6301\u9501：\u5b9e\u73b0\u7b2c\u4e00\u6b65\u5c31\u68c0\u67e5 _owner \u662f\u4e0d\u662f\u81ea\u5df1，\u4e0d\u662f\u5c31\u629b IllegalMonitorStateException\u3002<\/li>\n
            • wait() \u91ca\u653e\u7684\u662f"\u5168\u90e8"\u91cd\u5165：\u5148\u628a _recursions \u5b58\u8d77\u6765\u3001\u6e05\u96f6\u3001\u5f7b\u5e95\u9000\u51fa，\u9192\u6765\u91cd\u65b0\u62ff\u5230\u9501\u540e\u518d\u6062\u590d\u2014\u2014\u6240\u4ee5\u5728\u4e09\u5c42\u5d4c\u5957\u7684 synchronized \u91cc\u8c03\u7528 wait() \u4e5f\u4e0d\u4f1a\u6b7b\u9501\u3002<\/li>\n
            • notify() \u4e0d\u7acb\u5373\u5524\u9192\u4efb\u4f55\u4eba：\u5b83\u53ea\u662f\u628a\u7b49\u5f85\u8005\u4ece _WaitSet \u632a\u5230\u5165\u53e3\u961f\u5217\u3002\u88ab\u901a\u77e5\u7684\u7ebf\u7a0b\u8981\u7b49\u901a\u77e5\u8005\u9000\u51fa\u4e34\u754c\u533a\u3001\u5e76\u88ab\u9009\u4e3a\u7ee7\u4efb\u8005，\u624d\u4f1a\u88ab unpark\u3002\u8fd9\u5c31\u662f Mesa \u8bed\u4e49（signal-and-continue）\u5728\u6e90\u7801\u5c42\u9762\u7684\u6837\u5b50\u3002<\/li>\n
            • \u56e0\u4e3a\u53ea\u6709\u4e00\u4e2a _WaitSet，\u7b49\u4e0d\u540c\u6761\u4ef6\u7684\u7ebf\u7a0b\u6324\u5728\u4e00\u8d77，\u6240\u4ee5\u9ed8\u8ba4\u8981 notifyAll()；\u9700\u8981\u591a\u6761\u4ef6\u5c31\u7528 ReentrantLock + Condition，\u540e\u8005\u6bcf\u4e2a Condition \u6709\u81ea\u5df1\u7684\u7b49\u5f85\u961f\u5217\u3002<\/li>\n<\/ul>\n

              2.6 JVM \u600e\u4e48\u8854\u63a5\u5230 OS \u539f\u8bed<\/h4>\n

              HotSpot \u4e0d\u76f4\u63a5\u8c03\u7528 futex \u7cfb\u7edf\u8c03\u7528，\u800c\u662f\u901a\u8fc7\u5e73\u53f0\u5c42\u5c01\u88c5：<\/p>\n\nJava \u5c42HotSpot \u5185\u90e8Linux \u4e0a\u843d\u5230<\/tr>\n\n\n\n\n
              synchronized \u7ade\u4e89 \/ wait()<\/td>\nObjectMonitor \u2192 \u6bcf\u7ebf\u7a0b\u7684 ParkEvent \u2192 os::PlatformEvent::park()<\/td>\npthread_mutex + pthread_cond_wait<\/td>\n<\/tr>\n
              LockSupport.park()（AQS\u3001ReentrantLock\u3001Condition）<\/td>\n\u6bcf\u7ebf\u7a0b\u7684 Parker<\/td>\npthread_mutex + pthread_cond_(timed)wait<\/td>\n<\/tr>\n
              \u4e24\u8005\u5171\u540c<\/td>\nglibc NPTL<\/td>\nfutex(FUTEX_WAIT \/ FUTEX_WAKE) \u7cfb\u7edf\u8c03\u7528<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

              PlatformEvent \u81ea\u5df1\u4e5f\u5e26\u4e00\u4e2a\u5c0f\u8ba1\u6570\u5668\u4f5c\u5feb\u901f\u8def\u5f84：\u5982\u679c unpark \u5148\u4e8e park \u5230\u8fbe（"\u8bb8\u53ef"\u5df2\u7ecf\u7ed9\u4e86），park \u76f4\u63a5\u8fd4\u56de，\u6839\u672c\u4e0d\u78b0 pthread\u3002\u53ea\u6709\u771f\u8981\u7761\u65f6\u624d\u8fdb\u5165 pthread_cond_wait，\u518d\u7531 glibc \u8d70\u5230 futex_wait，\u6700\u540e\u8fdb\u5165\u7b2c\u4e00\u90e8\u5206\u8bb2\u7684\u5185\u6838\u7b49\u5f85\u961f\u5217\u548c\u8c03\u5ea6\u5668\u3002\u6240\u4ee5\u5b8c\u6574\u94fe\u6761\u662f：<\/p>\n

              synchronized \u7ade\u4e89
              \n \u2192 CAS \u5931\u8d25 \u2192 \u81ea\u65cb\u5931\u8d25 \u2192 ObjectMonitor \u5165\u961f
              \n \u2192 ParkEvent::park \u2192 pthread_cond_wait
              \n \u2192 futex(FUTEX_WAIT) \u7cfb\u7edf\u8c03\u7528 \u2190 \u7b2c\u4e00\u6b21\u8fdb\u5165\u5185\u6838\u6001
              \n \u2192 \u5185\u6838：\u5165\u54c8\u5e0c\u6876\u7b49\u5f85\u961f\u5217，schedule() \u5207\u8d70
              \n\u2026
              \n\u6301\u6709\u8005 exit \u2192 unpark \u7ee7\u4efb\u8005 \u2192 pthread_cond_signal
              \n \u2192 futex(FUTEX_WAKE) \u2190 \u5524\u9192\u65b9\u8fdb\u5165\u5185\u6838\u6001
              \n \u2192 try_to_wake_up() \u2192 \u7ee7\u4efb\u8005\u56de\u5230\u8fd0\u884c\u961f\u5217<\/p>\n

              \u5728 macOS \u4e0a，pthread \u5e95\u5c42\u4e0d\u662f futex，\u800c\u662f Darwin \u5185\u6838\u7684 psynch \u7cfb\u5217\u7cfb\u7edf\u8c03\u7528，\u4f46\u7ed3\u6784\u76f8\u540c\u3002<\/p>\n

              2.7 \u865a\u62df\u7ebf\u7a0b：\u628a"\u7761\u7720"\u4ece\u5185\u6838\u632a\u5230 JVM<\/h4>\n

              \u865a\u62df\u7ebf\u7a0b（JEP 444，JDK 21）\u5728\u963b\u585e\u65f6\u4e0d\u8d70\u4e0a\u9762\u90a3\u6761\u901a\u5f80 futex \u7684\u8def：\u5b83\u628a\u81ea\u5df1\u7684\u6808\u5e27\u4f5c\u4e3a continuation \u4fdd\u5b58\u5230\u5806\u4e0a，\u4ece\u627f\u8f7d\u5b83\u7684\u5e73\u53f0\u7ebf\u7a0b\u4e0a\u5378\u8f7d（unmount），\u5e73\u53f0\u7ebf\u7a0b\u7ee7\u7eed\u53bb\u8dd1\u522b\u7684\u865a\u62df\u7ebf\u7a0b\u3002\u5524\u9192\u65f6\u7531 JVM \u7684\u8c03\u5ea6\u5668（\u4e00\u4e2a ForkJoinPool）\u628a\u5b83\u91cd\u65b0\u6302\u8f7d\u5230\u67d0\u4e2a\u5e73\u53f0\u7ebf\u7a0b\u4e0a\u3002<\/p>\n

              JDK 21\u201323 \u4e2d，synchronized \u91cc\u963b\u585e\u4f1a\u628a\u627f\u8f7d\u7ebf\u7a0b\u9489\u4f4f（pinning），\u539f\u56e0\u4e4b\u4e00\u6b63\u662f\u65e7\u5b9e\u73b0\u628a\u9501\u548c"\u67d0\u4e2a\u5e73\u53f0\u7ebf\u7a0b \/ \u67d0\u4e2a\u7ebf\u7a0b\u6808"\u7ed1\u5728\u4e00\u8d77；JEP 491（JDK 24）\u91cd\u5199\u4e86 ObjectMonitor \u7684 owner \u8bb0\u5f55\u65b9\u5f0f，\u5927\u90e8\u5206\u60c5\u51b5\u4e0b synchronized \u4e5f\u80fd\u5378\u8f7d\u4e86\u3002\u4ecd\u7136\u4f1a\u9489\u4f4f\u7684\u60c5\u51b5\u5305\u62ec：\u6808\u4e0a\u6709\u672c\u5730\u65b9\u6cd5\u5e27，\u4ee5\u53ca\u7c7b\u521d\u59cb\u5316\u671f\u95f4\u3002<\/p>\n

              \u7b2c\u4e09\u90e8\u5206：\u4e24\u5c42\u5b9e\u73b0\u5e76\u6392\u5bf9\u7167<\/h3>\n\n\u673a\u5236\u95ee\u9898\u64cd\u4f5c\u7cfb\u7edf \/ \u7ebf\u7a0b\u5e93HotSpot synchronized<\/tr>\n\n\n\n\n\n\n\n\n\n\n\n\n
              \u4e92\u65a5\u7684\u539f\u5b50\u6027<\/td>\n\u786c\u4ef6\u539f\u5b50\u6307\u4ee4（LOCK CMPXCHG\u3001LL\/SC）；\u5355\u6838\u53ef\u5173\u4e2d\u65ad<\/td>\n\u540c\u6837\u7684 CAS，\u4f5c\u7528\u5728 Mark Word \u6216 _owner \u4e0a<\/td>\n<\/tr>\n
              \u65e0\u7ade\u4e89\u5feb\u901f\u8def\u5f84<\/td>\nfutex \u9501：\u4e00\u6b21\u7528\u6237\u6001 CAS，\u96f6\u7cfb\u7edf\u8c03\u7528<\/td>\n\u8f7b\u91cf\u7ea7\u9501：\u4e00\u6b21 CAS（\u504f\u5411\u9501\u65f6\u4ee3\u8fde CAS \u90fd\u7701\u4e86）<\/td>\n<\/tr>\n
              \u77ed\u6682\u7ade\u4e89<\/td>\n\u5185\u6838 mutex \u4e50\u89c2\u81ea\u65cb；glibc \u81ea\u9002\u5e94\u81ea\u65cb\u9501\u53ef\u9009<\/td>\nObjectMonitor \u81ea\u9002\u5e94\u81ea\u65cb<\/td>\n<\/tr>\n
              \u5165\u53e3\u961f\u5217<\/td>\n\u5185\u6838 wait_list \/ futex \u54c8\u5e0c\u6876\u961f\u5217<\/td>\n_cxq + _EntryList<\/td>\n<\/tr>\n
              \u6761\u4ef6\u53d8\u91cf<\/td>\npthread_cond：\u5e8f\u53f7 + futex<\/td>\n_WaitSet（\u6bcf\u5bf9\u8c61\u4ec5\u4e00\u4e2a）<\/td>\n<\/tr>\n
              \u9632\u4e22\u5931\u5524\u9192<\/td>\n\u201c\u5148\u5165\u961f\/\u8bb0\u5e8f\u53f7，\u518d\u67e5\u6761\u4ef6，\u518d\u7761\u201d，\u5185\u6838\u5185\u539f\u5b50\u68c0\u67e5<\/td>\n\u5165 _WaitSet \u540e\u624d\u91ca\u653e\u9501；ParkEvent \u8bb8\u53ef\u8ba1\u6570<\/td>\n<\/tr>\n
              \u6302\u8d77<\/td>\n\u79fb\u51fa\u8fd0\u884c\u961f\u5217 + \u4e0a\u4e0b\u6587\u5207\u6362<\/td>\npark \u2192 pthread_cond_wait \u2192 futex<\/td>\n<\/tr>\n
              \u5524\u9192<\/td>\n\u653e\u56de\u8fd0\u884c\u961f\u5217，\u5fc5\u8981\u65f6\u53d1 IPI<\/td>\n\u9009\u4e00\u4e2a\u7ee7\u4efb\u8005 unpark \u2192 futex wake<\/td>\n<\/tr>\n
              \u5524\u9192\u8bed\u4e49<\/td>\nMesa（pthreads）<\/td>\nMesa<\/td>\n<\/tr>\n
              \u516c\u5e73\u6027<\/td>\n\u4e00\u822c\u4e0d\u4fdd\u8bc1<\/td>\n\u4e0d\u4fdd\u8bc1，\u5141\u8bb8\u63d2\u961f<\/td>\n<\/tr>\n
              \u5185\u6838\u6001\u5207\u6362\u4f55\u65f6\u53d1\u751f<\/td>\n\u53ea\u5728\u771f\u8981\u7761 \/ \u771f\u8981\u5524\u9192\u65f6<\/td>\n\u53ea\u5728\u81a8\u80c0\u540e\u771f\u8981 park \/ unpark \u65f6<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

              \u7b2c\u56db\u90e8\u5206：\u4e0e\u59ca\u59b9\u7bc7\u7684\u5bf9\u7167<\/h3>\n\n\u4e3b\u9898\u300a\u4ece PV \u64cd\u4f5c\u3001\u7ba1\u7a0b\u5230\u73b0\u4ee3 Java \u5e76\u53d1\u300b\u672c\u6587<\/tr>\n\n\n\n\n\n\n\n\n\n
              \u7ba1\u7a0b\u5b9a\u4e49\u3001Hoare vs. Mesa<\/td>\n\u5df2\u8986\u76d6<\/td>\n\u8865\u5145：\u4e24\u79cd\u8bed\u4e49\u7684\u5b9e\u73b0\u4ee3\u4ef7（1.4）<\/td>\n<\/tr>\n
              synchronized \/ wait \/ notify \u7684\u7528\u6cd5\u4e0e\u89c4\u77e9<\/td>\n\u5df2\u8986\u76d6<\/td>\n\u8865\u5145：\u6bcf\u6761\u89c4\u77e9\u5728 ObjectMonitor \u6e90\u7801\u5c42\u9762\u7684\u51fa\u5904（2.5）<\/td>\n<\/tr>\n
              AQS\u3001Condition\u3001Semaphore<\/td>\n\u5df2\u8986\u76d6<\/td>\n\u53ea\u8bb2\u5b83\u4eec\u5171\u4eab\u7684 park \u843d\u5730\u8def\u5f84（2.6）<\/td>\n<\/tr>\n
              \u539f\u5b50\u6307\u4ee4\u3001\u81ea\u65cb\u9501\u3001\u5185\u6838\u7b49\u5f85\u961f\u5217\u3001\u4e22\u5931\u5524\u9192<\/td>\n\u672a\u8986\u76d6<\/td>\n1.1\u20131.3<\/td>\n<\/tr>\n
              futex \u5feb\u6162\u8def\u5f84\u3001pthread_cond<\/td>\n\u53ea\u63d0\u5230\u540d\u5b57<\/td>\n1.5\u20131.6<\/td>\n<\/tr>\n
              Mark Word\u3001\u9501\u5347\u7ea7\u3001\u81a8\u80c0\u4e0e\u6536\u7f29<\/td>\n\u4e00\u53e5\u8bdd\u5e26\u8fc7<\/td>\n2.2\u20132.3<\/td>\n<\/tr>\n
              ObjectMonitor \u7ed3\u6784\u3001\u63d2\u961f\u4e0e\u516c\u5e73\u6027<\/td>\n\u672a\u8986\u76d6<\/td>\n2.4<\/td>\n<\/tr>\n
              \u865a\u62df\u7ebf\u7a0b<\/td>\n\u5df2\u8986\u76d6（\u5378\u8f7d\u4e0e\u9489\u4f4f）<\/td>\n\u8865\u5145：\u9489\u4f4f\u7684\u5b9e\u73b0\u539f\u56e0（2.7）<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

              \u59ca\u59b9\u7bc7\u91cc\u6709\u4e24\u5904\u8bf4\u6cd5\u504f\u7b80\u5316，\u672c\u6b21\u5df2\u5728\u539f\u6587\u4fee\u6b63：<\/p>\n

            • \u201cLockSupport.park\/unpark \u2192 futex\u201d：HotSpot \u5e76\u4e0d\u76f4\u63a5\u8c03\u7528 futex，\u4e2d\u95f4\u9694\u7740 Parker \/ PlatformEvent \u548c glibc \u7684 pthread_mutex \/ pthread_cond，\u540e\u8005\u5728 Linux \u4e0a\u624d\u843d\u5230 futex\u3002<\/li>\n
            • \u201c\u504f\u5411\u9501\u5df2\u7531 JEP 374 \u5728 JDK 15 \u4e2d\u5e9f\u5f03\u5e76\u9ed8\u8ba4\u5173\u95ed\u201d：\u6ca1\u9519，\u4f46\u4e0d\u5b8c\u6574\u2014\u2014JDK 18 \u5df2\u6dd8\u6c70\u76f8\u5173\u53c2\u6570\u3001\u79fb\u9664\u5b9e\u73b0\u3002\u6240\u4ee5\u7f51\u4e0a\u5e38\u89c1\u7684"\u504f\u5411 \u2192 \u8f7b\u91cf \u2192 \u91cd\u91cf"\u4e09\u6bb5\u5347\u7ea7，\u53ea\u9002\u7528\u4e8e JDK 15 \u4e4b\u524d\u7684\u9ed8\u8ba4\u914d\u7f6e\u3002<\/li>\n

              \u7ed3\u8bba<\/h3>\n
                \n
              • \u7ba1\u7a0b\u4e0d\u662f\u5185\u6838\u5bf9\u8c61，\u800c\u662f\u7528\u9501 + \u7b49\u5f85\u961f\u5217\u62fc\u51fa\u6765\u7684\u8bed\u8a00\u7ed3\u6784\u3002 OS \u63d0\u4f9b\u7684\u662f\u539f\u5b50\u6307\u4ee4\u3001futex\u3001\u7b49\u5f85\u961f\u5217\u548c\u8c03\u5ea6\u5668；\u7f16\u8bd1\u5668\u548c\u8fd0\u884c\u65f6\u8d1f\u8d23\u628a\u5b83\u4eec\u7ec4\u88c5\u6210"\u9690\u5f0f\u4e92\u65a5 + \u6761\u4ef6\u53d8\u91cf"\u3002<\/li>\n
              • \u6240\u6709\u5c42\u90fd\u5728\u7528\u540c\u4e00\u4e2a\u4e09\u6bb5\u5f0f：\u5148 CAS（\u7eaf\u7528\u6237\u6001）\u2192 \u518d\u81ea\u65cb（\u8d4c\u6301\u6709\u8005\u9a6c\u4e0a\u91ca\u653e）\u2192 \u6700\u540e\u6392\u961f\u7761\u7720（\u8fdb\u5185\u6838）\u3002\u5185\u6838 mutex\u3001futex \u9501\u3001glibc\u3001HotSpot ObjectMonitor \u83ab\u4e0d\u5982\u6b64\u3002<\/li>\n
              • \u9632\u4e22\u5931\u5524\u9192\u53ea\u6709\u4e00\u4e2a\u6838\u5fc3\u6280\u5de7：\u5148\u767b\u8bb0\u81ea\u5df1\u8981\u7b49（\u5165\u961f\u6216\u8bb0\u4e0b\u5e8f\u53f7），\u518d\u68c0\u67e5\u6761\u4ef6，\u6700\u540e\u7761；\u68c0\u67e5\u548c\u5165\u7761\u5728\u5185\u6838\u91cc\u539f\u5b50\u5b8c\u6210\u3002<\/li>\n
              • \u7528\u6237\u6001 \/ \u5185\u6838\u6001\u5207\u6362\u53ea\u53d1\u751f\u5728\u771f\u7ade\u4e89\u65f6\u3002 \u65e0\u7ade\u4e89\u7684 synchronized \u662f\u4e00\u6b21 CAS；\u53ea\u6709\u81a8\u80c0\u4e3a\u91cd\u91cf\u7ea7\u9501\u3001\u5e76\u4e14\u771f\u7684\u8981 park \/ unpark \u65f6，\u624d\u901a\u8fc7 pthread_cond \u8d70\u5230 futex \u7cfb\u7edf\u8c03\u7528\u3002<\/li>\n
              • Java \u7684\u7ba1\u7a0b\u662f"\u6309\u9700\u5b9e\u4f53\u5316"\u7684：\u5e73\u65f6\u53ea\u662f Mark Word \u91cc\u7684\u51e0\u4e2a\u4f4d，\u9700\u8981\u6392\u961f\u6216 wait() \u65f6\u624d\u81a8\u80c0\u51fa ObjectMonitor，\u7a7a\u95f2\u540e\u53c8\u88ab\u5f02\u6b65\u6536\u7f29\u3002\u504f\u5411\u9501\u5df2\u6210\u5386\u53f2，JDK 23 \u8d77\u8f7b\u91cf\u7ea7\u9501\u4e5f\u6362\u6210\u4e86 lock-stack \u5b9e\u73b0\u3002<\/li>\n
              • Mesa \u8bed\u4e49\u6709\u7269\u7406\u6839\u6e90：\u5185\u6838\u5524\u9192\u53ea\u662f\u8ba9\u7ebf\u7a0b\u53d8\u6210\u53ef\u8fd0\u884c，notify() \u53ea\u662f\u628a\u7ebf\u7a0b\u632a\u56de\u5165\u53e3\u961f\u5217\u2014\u2014\u9192\u6765\u65f6\u6761\u4ef6\u65e9\u5df2\u53ef\u80fd\u53d8\u4e86，\u6240\u4ee5\u6c38\u8fdc\u5199 while\u3002<\/li>\n<\/ul>\n

                \u53c2\u8003\u8d44\u6599<\/h3>\n
                  \n
                • C. A. R. Hoare, \u201cMonitors: An Operating System Structuring Concept\u201d, Communications of the ACM, 1974（\u542b\u7528\u4fe1\u53f7\u91cf\u5b9e\u73b0\u7ba1\u7a0b\u7684\u6784\u9020）\u3002<\/li>\n
                • B. Lampson, D. Redell, \u201cExperience with Processes and Monitors in Mesa\u201d, Communications of the ACM, 1980\u3002<\/li>\n
                • A. Silberschatz \u7b49，Operating System Concepts，\u201cMonitors\u201d \u4e0e \u201cImplementing a Monitor Using Semaphores\u201d \u5c0f\u8282\u3002<\/li>\n
                • H. Franke, R. Russell, M. Kirkwood, \u201cFuss, Futexes and Furwocks: Fast Userlevel Locking in Linux\u201d, Ottawa Linux Symposium, 2002\u3002<\/li>\n
                • U. Drepper, \u201cFutexes Are Tricky\u201d, 2011\u3002<\/li>\n
                • Linux \u5185\u6838\u6587\u6863：Documentation\/locking\/mutex-design.rst；man 2 futex\u3002<\/li>\n
                • OpenJDK HotSpot \u6e90\u7801：src\/hotspot\/share\/runtime\/objectMonitor.{hpp,cpp}\u3001synchronizer.cpp\u3001lockStack.hpp\u3001os\/posix\/os_posix.cpp（PlatformEvent\u3001Parker）\u3002<\/li>\n
                • JEP 374（\u5e9f\u5f03\u5e76\u7981\u7528\u504f\u5411\u9501）\u3001JEP 444（\u865a\u62df\u7ebf\u7a0b）\u3001JEP 450 \/ JEP 519（\u7d27\u51d1\u5bf9\u8c61\u5934）\u3001JEP 491（\u865a\u62df\u7ebf\u7a0b\u540c\u6b65\u4e0d\u518d\u9489\u4f4f）\u3002<\/li>\n
                • D. Dice, \u201cBiased Locking in HotSpot\u201d；OpenJDK Wiki \u201cSynchronization\u201d\u3002<\/li>\n
                • \u59ca\u59b9\u7bc7：\u4ece PV \u64cd\u4f5c\u3001\u7ba1\u7a0b\u5230\u73b0\u4ee3 Java \u5e76\u53d1\u3002<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"

                  English version: How Monitors Are Implemented: From the OS Kernel to the HotSpot ObjectMonitor
                  \n\u59ca\u59b9\u7bc7 \u4ece PV \u64cd\u4f5c\u3001\u7ba1\u7a0b\u5230\u73b0\u4ee3 Java \u5e76\u53d1 \u8bb2\u7684\u662f\u7ba1\u7a0b\u662f\u4ec0\u4e48：\u5171\u4eab\u6570\u636e \u8fc7\u7a0b \u9690\u5f0f\u4e92\u65a5 \u6761\u4ef6\u53d8\u91cf，\u4ee5\u53ca Hoare \/ Mesa \u4e24\u79cd\u5524\u9192\u8bed\u4e49\u3002\u672c\u6587\u53ea\u56de\u7b54\u4e0b\u4e00\u4e2a\u95ee\u9898：\u5b83\u662f\u600e\u4e48\u505a\u51fa\u6765\u7684\u2014\u2014\u4ece\u4e00\u6761 CPU \u539f\u5b50\u6307\u4ee4\u5f00\u59cb，\u7ecf<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[99],"topic":[],"class_list":["post-117864","post","type-post","status-publish","format-standard","hentry","category-server","tag-java"],"yoast_head":"\n\u7ba1\u7a0b\u662f\u600e\u4e48\u5b9e\u73b0\u7684\uff1a\u4ece\u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u5230 HotSpot \u5bf9\u8c61\u76d1\u89c6\u5668 - 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