{"id":1225,"date":"2010-08-27T18:13:43","date_gmt":"2010-08-27T10:13:43","guid":{"rendered":"http:\/\/edsionte.com\/techblog\/?p=1225"},"modified":"2010-09-24T13:47:15","modified_gmt":"2010-09-24T05:47:15","slug":"ipc-under-linux-share-memory","status":"publish","type":"post","link":"http:\/\/edsionte.com\/techblog\/archives\/1225","title":{"rendered":"IPC under Linux-Shared Memory"},"content":{"rendered":"

\u8fd8\u8bb0\u5f97\u5728\u4e0a\u7bc7\u6587\u7ae0\u4e2d\u6211\u4eec\u8bf4\u5230\u7684N\u4e2a\u5b50\u8fdb\u7a0b\u72ec\u81ea\u8bbf\u95ee\u81ea\u5df1\u7684\u4e34\u754c\u533a\u5417\uff0c\u90a3\u4e48\u4eca\u5929\u8981\u8bf4\u7684\u5171\u4eab\u5185\u5b58\u5c31\u53ef\u4ee5\u5b9e\u73b0\u591a\u4e2a\u8fdb\u7a0b\u90fd\u53bb\u8bbf\u95ee\u4e00\u5757\u5185\u5b58<\/strong>\uff01 \"et2\" \u5982\u679c\u4f60\u5bf9\u6211\u4eec\u524d\u9762\u6240\u8bf4\u7684\u51e0\u79cdIPC\u65b9\u5f0f\u90fd\u4e86\u89e3\uff0c\u90a3\u4e48\u5173\u4e8e\u5171\u4eab\u5185\u5b58\u7684\u57fa\u672c\u77e5\u8bc6\u4f60\u5c31\u6709\u4f3c\u66fe\u76f8\u8bc6\u7684\u611f\u89c9\u3002\u6211\u4eec\u5feb\u901f\u5165\u95e8\u5427 \"e91\" \uff01<\/p>\n

1.\u5982\u4f55\u521b\u5efa\u4e00\u5757\u5171\u4eab\u5185\u5b58\uff1f<\/p>\n

\u5176\u5b9e\u5217\u51fa\u51fd\u6570\u539f\u578b\uff0c\u4f60\u5e94\u8be5\u4f1a\u77e5\u9053\u6bcf\u4e2a\u53c2\u6570\u7684\u542b\u4e49\u3002<\/p>\n

int shmget(key_t key,size_t size,int shmflg);<\/pre>\n
\u8fd9\u91cc\u8981\u8bf4\u660e\u7684\u662fsize\u7684\u5927\u5c0f\uff0c\u5982\u679c\u521b\u5efa\u4e00\u5757\u65b0\u7684\u5171\u4eab\u5185\u5b58\u533a\uff0c\u90a3\u4e48size\u5fc5\u987b\u5927\u4e8e0\uff1b\u5982\u679csize\u4e3a0\uff0c\u90a3\u6b64\u65f6shmget\u51fd\u6570\u7684\u529f\u80fd\u5c31\u662f\u6253\u5f00\u4e00\u4e2a\u5df2\u5b58\u5728\u7684\u5171\u4eab\u5185\u5b58\u533a\uff08\u5f53\u7136\uff0ckey\u4ee3\u8868\u7684\u5185\u5b58\u533a\u662f\u5426\u5b58\u5728\u90a3\u662f\u4e8c\u8bdd\uff09\u3002size\u4e3a\u8d1f\uff0c\u90a3\u4e48\u8c03\u7528\u51fa\u9519\uff0c\u8fd4\u56de-1\u3002\u53e6\u5916shmflg\u7684\u53d6\u503c\u4ee5\u53ca\u7528\u6cd5\u90fd\u4e0e\u4fe1\u53f7\u91cf\u76f8\u540c\uff0c\u53ef\u53c2\u8003\u524d\u9762\u7684\u6587\u7ae0\u3002<\/p>\n
\u5f53shmget\u8c03\u7528\u6210\u529f\u540e\uff0c\u8fd4\u56de\u6574\u5f62id\u3002<\/p>\n
2.\u5171\u4eab\u5185\u5b58\u521b\u5efa\u597d\u4e86\uff0c\u8fdb\u7a0b\u5982\u4f55\u4f7f\u7528\uff1f<\/p>\n
\u6211\u4eec\u521b\u5efa\u597d\u4e86\u5185\u5b58\u5757\uff0c\u4f46\u662f\u521b\u5efa\u8fdb\u7a0b\u6b64\u65f6\u548c\u8fd9\u5757\u5185\u5b58\u8fd8\u6ca1\u8054\u7cfb\u3002\u6240\u4ee5\uff0c\u6211\u4eec\u5e94\u8be5\u4f7f\u7528shmat\u51fd\u6570\u5c06\u5176\u9644\u52a0\u5230\u8fdb\u7a0b\u7684\u5730\u5740\u7a7a\u95f4\uff08\u5177\u4f53\u4f4d\u4e8e\u8fdb\u7a0b\u7684\u5806\u6808\u6bb5\uff09\u3002<\/p>\n
void* shmat(int shmid,const void* shmaddr,int shmflg);<\/pre>\n
\u4e00\u822c\u6211\u4eec\u5c06shmaddr\u7f6e\u4e3aNULL\uff0c\u56e0\u4e3a\u6b64\u65f6\u5185\u5b58\u4f1a\u81ea\u52a8\u5206\u914d\u4e00\u6bb5\u4f55\u65f6\u7684\u5185\u5b58\u5757\u3002\u5e76\u4e14\u6700\u7ec8shmat\u51fd\u6570\u5c06\u8fd4\u56de\u8fd9\u4e2a\u5185\u5b58\u5757\u7684\u9996\u5730\u5740\u3002\u4e5f\u8bb8\u4f60\u5bf9\u6b64\u5904\u7684void\u7c7b\u578b\u6bd4\u8f83\u4e0d\u89e3\uff0c\u5176\u5b9evoid* shmaddr\u8fd9\u6837\u7684\u5b9a\u4e49\u65b9\u5f0f\u5176\u5b9e\u662f\u4e3a\u4e86\u7075\u6d3b\u4f7f\u7528\uff1a\u9996\u5148shmaddr\u662f\u4e00\u4e2a\u6307\u9488\u7c7b\u578b\uff08\u5185\u5b58\u5730\u5740\uff09\uff0c\u4f46\u5176\u5177\u4f53\u662f\u6307\u5411\u4f55\u79cd\u7c7b\u578b\u7684\u6307\u9488\uff0c\u5728\u6b64\u5e76\u4e0d\u5177\u4f53\u8bf4\u660e\u3002\u56e0\u4e3a\u5f53\u4f60\u8981\u4f7f\u7528\u8fd9\u4e2a\u6307\u9488\u65f6\uff0c\u53ef\u4ee5\u7528\u4efb\u4f55\u7c7b\u578b\u5f3a\u5236\u8f6c\u6362\u3002<\/p>\n
\u4e0e\u6b64\u51fd\u6570\u5bf9\u5e94\u7684\u662fshmdt\u51fd\u6570\uff0c\u5b83\u4f1a\u8ba9\u8c03\u7528\u8fdb\u7a0b\u4e0eshmaddr\u6307\u5411\u7684\u5171\u4eab\u5185\u5b58\u8131\u79bb\u3002<\/p>\n
3.\u5bf9\u5171\u4eab\u5185\u5b58\u7684\u63a7\u5236\uff1f<\/p>\n
int shmctl(int shmid,int cmd,struct shmid_ds *buf);<\/pre>\n
cmd\u53ef\u53d6\u503c\uff1aIPC_RMID,IPC_SET,IPC_STAT\u5206\u522b\u5bf9\u5e94\uff1a\u5220\u9664\u5171\u4eab\u5185\u5b58\u533a\uff0c\u8bbe\u7f6e\u5171\u4eab\u5185\u5b58\u533a\u7684shmid_ds\u7ed3\u6784\uff0c\u83b7\u53d6shmid_ds\u7ed3\u6784\u3002\u8fd9\u91cc\u4e0d\u518d\u8d58\u8ff0\u5177\u4f53\u4f7f\u7528\u65b9\u6cd5\uff0c\u53ef\u53c2\u8003man\u624b\u518c\u3002<\/p>\n
\u4ecb\u7ecd\u5b8c\u8fd9\u4e9b\uff0c\u6211\u4eec\u7684\u91cd\u70b9\u5c31\u662f\u8981\u5b66\u4f1a\u5e94\u7528\u5171\u4eab\u5185\u5b58\u3002\u300alinuxC\u7f16\u7a0b\u5b9e\u6218\u300b\u4e00\u4e66\u4e2d\u7684\u4f8b10-17\u975e\u5e38\u7ecf\u5178\uff0c\u53ef\u4ee5\u6a21\u62df\u8fdb\u7a0b\u4e4b\u95f4\u7684\u540c\u6b65\u3002\u8be5\u4f8b\u8fd8\u7279\u522b\u7684\u5b9a\u4e49\u4e86\u4e00\u4e2a\u5934\u6587\u4ef6shm.h\uff0c\u6b64\u5934\u6587\u4ef6\u4e2d\u52a0\u5165\u4e86\u8bb8\u591a\u5bf9\u4fe1\u53f7\u91cf\u4ee5\u53ca\u5171\u4eab\u5185\u5b58\u7684\u64cd\u4f5c\u51fd\u6570\u3002\u73b0\u5728\u6211\u4eec\u5177\u4f53\u6765\u5206\u6790\uff0c\u54ea\u4e9b\u8bed\u53e5\u5b9e\u73b0\u8fdb\u7a0b\u7684\u4e92\u65a5\uff0c\u54ea\u4e9b\u8bed\u53e5\u5b9e\u73b0\u7684\u662f\u8fdb\u7a0b\u7684\u540c\u6b65\u3002<\/p>\n
\u9996\u5148\uff0c\u4e0d\u7ba1\u662f\u8bfb\u8fdb\u7a0b\uff0c\u8fd8\u662f\u5199\u8fdb\u7a0b\uff0cPV\u64cd\u4f5c\u4e4b\u95f4\u7684\u4ee3\u7801\u90fd\u5c5e\u4e8e\u4e34\u754c\u533a\u3002\u4e34\u754c\u533a\u7684\u4ee3\u7801\u90fd\u662f\u5bf9\u5171\u4eab\u5185\u5b58\u53bb\u8fdb\u884c\u64cd\u4f5c\uff0c\u6240\u4ee5\u5e94\u8be5\u52a0\u4e0aPV\u64cd\u4f5c\uff0c\u907f\u514d\u8bfb\u5199\u8fdb\u7a0b\u4ea4\u4e92\u5bf9\u5171\u4eab\u5185\u5b58\u8fdb\u884c\u8bbf\u95ee\u3002\u6240\u4ee5\u8bfb\u5199\u7a0b\u5e8f\u4e2d\u7684PV\u64cd\u4f5c\u5b9e\u73b0\u7684\u662f\u8fdb\u7a0b\u7684\u4e92\u65a5\u3002<\/p>\n
\u6211\u4eec\u8fd8\u53ef\u4ee5\u53d1\u73b0\uff0c\u8bfb\u5199\u8fdb\u7a0b\u4ee3\u7801\u4e2d\u90fd\u6709waitsem(semid,0)\u8bed\u53e5\u3002\u4ee5\u5199\u8fdb\u7a0b\u4e3a\u4f8b\uff0c\u6bcf\u6b21\u5199\u5185\u5b58\u65f6\uff0c\u90fd\u8981\u67e5\u770b\u4fe1\u53f7\u91cf\uff08semid\u4fe1\u53f7\u91cf\u96c6\u4e2d\u76840\u53f7\u4fe1\u53f7\u91cf\uff09\u662f\u5426\u4e3a1\u3002\u5982\u679c\u4e3a1\uff0c\u8bf4\u660e\u6b64\u65f6\u6ca1\u6709\u8bfb\u8fdb\u7a0b\u8bbf\u95ee\u5171\u4eab\u5185\u5b58\uff1b\u5426\u5219\uff0c\u8bf4\u660e\u6709\u8bfb\u8fdb\u7a0b\u5728\u8bbf\u95ee\uff0c\u6b64\u65f6\u5199\u8fdb\u7a0b\u672c\u5e94\u8be5\u963b\u585e\uff0c\u4f46\u662f\u8fd9\u91cc\u6211\u4eec\u7528sleep(1)\u6765\u6a21\u62df\u8fdb\u7a0b\u7684\u963b\u585e\uff0c\u800c\u4e14\u4e0d\u65ad\u7684\u53bb\u6d4b\u8bd5\u4fe1\u53f7\u91cf\u662f\u5426\u4e3a1\u3002<\/p>\n
\u5982\u679c\u5199\u8fdb\u7a0b\u6210\u529f\u8fdb\u5165\u4e34\u754c\u533a\uff0c\u90a3\u4e48\u5b83\u5c06\u5199\u6570\u636e\u81f3\u5171\u4eab\u5185\u5b58\u3002\u53ef\u80fd\u4f60\u5bf9\u4e8estrcpy(shmaddr,wbuf);\u8fd9\u6837\u7684\u8bed\u53e5\u611f\u5230\u56f0\u60d1\uff1a\u600e\u4e48\u80fd\u5c06wbuf\u8d4b\u503c\u7ed9\u5171\u4eab\u5185\u5b58\uff1f\uff01\u5176\u5b9e\u4ed4\u7ec6\u60f3\u60f3\uff0c\u8fd9\u6ca1\u6709\u4ec0\u4e48\u4e0d\u5408\u7406\u3002shmaddr\u662f\u4e00\u4e2a\u6307\u9488\uff0cwbuf\u662f\u4e00\u4e2a\u5b57\u7b26\u4e32\u6570\u7ec4\u7684\u9996\u5b57\u7b26\u7684\u9996\u5730\u5740\uff0c\u90a3\u4e48strcpy\u51fd\u6570\u6240\u505a\u7684\u5c31\u662f\u5f88\u5e73\u5e38\u7684\u4e8b\u4e86\u3002\u540c\u65f6\uff0c\u6211\u4eec\u4e5f\u53ef\u4ee5\u8fd9\u4e48\u60f3\uff1a\u4e00\u822c\u6211\u4eec\u90fd\u662f\u63d0\u524d\u7528malloc\u6765\u5206\u914d\u5185\u5b58\u7a7a\u95f4\uff0c\u518d\u8ba9\u67d0\u4e2a\u6307\u9488\u6307\u5411\u8fd9\u7247\u5185\u5b58\u7a7a\u95f4\uff0c\u800c\u73b0\u5728\uff0c\u4e0a\u9762\u7684shmget\u4ee5\u53cashat\u4ee5\u53ca\u5b8c\u6210\u4e86\u7c7b\u4f3cmalloc\u7684\u5de5\u4f5c\u3002<\/p>\n
\u5176\u5b9e\u6211\u4eec\u6709\u8fd9\u6837\u7684\u60f3\u6cd5\u5f88\u81ea\u7136\uff0c\u6bd5\u7adf\u521a\u5f00\u59cb\u5b66\u4e60\uff0c\u901a\u8fc7\u5b9e\u8df5\u53ef\u4ee5\u4ece\u611f\u6027\u4e0a\u8ba4\u8bc6\u8fd9\u4e9b\u3002<\/p>\n
\u90a3\u4e48\u5f88\u663e\u7136\uff0cwaitsem(semid,0)\u8bed\u53e5\u5b9e\u73b0\u7684\u4fbf\u662f\u8bfb\u5199\u8fdb\u7a0b\u7684\u540c\u6b65\u95ee\u9898\u2014\u2014\u534f\u8c03\u8bfb\u5199\u8fdb\u7a0b\u5bf9\u5171\u4eab\u5185\u5b58\u7684\u8bbf\u95ee\u3002<\/p>\n
\/\/\u5199\u8fdb\u7a0b\u90e8\u5206\u4ee3\u7801\r\n\twhile(1)\r\n\t{\r\n                waitsem(semid,0);\r\n\t\tp(semid,0);\r\n\t\tprintf(\"writer:\");\r\n\t\tfgets(wbuf,1024,stdin);\r\n\t\twbuf[strlen(wbuf)-1]='\\0';\r\n\t\tstrcpy(shmaddr,wbuf);\r\n\t\tmy_sleep(5);\r\n\t\tv(semid,0);\r\n\t\tmy_sleep(3);\r\n\t}\r\n\/\/\u8bfb\u8fdb\u7a0b\u90e8\u5206\u4ee3\u7801\r\n\twhile(1)\r\n\t{\r\n                waitsem(semid,0);\r\n\t\tp(semid,0);\r\n\t\tprintf(\"reader:\");\r\n\t\tprintf(\"%s\\n\",shmaddr);\r\n\t\tmy_sleep(5);\r\n\t\tv(semid,0);\r\n\t\tmy_sleep(3);\r\n\t}<\/pre>\n
\u7406\u89e3\u4e86\u8fd9\u4e2a\u7a0b\u5e8f\u8981\u5e72\u4ec0\u4e48\uff0c\u90a3\u4e48\u6211\u4eec\u518d\u6765\u60f3\u60f3\u5b83\u4e3a\u4ec0\u4e48\u8981\u8fd9\u4e48\u505a\uff1a\u8bfb\u5199\u8fdb\u7a0b\u4e2d\u4e3a\u4f55\u8981\u52a0\u5165sleep\u51fd\u6570\uff1f\u90a3\u6211\u4eec\u6765\u505a\u51e0\u4e2a\u6d4b\u8bd5\u5427\u3002\u5728\u6d4b\u8bd5\u4e4b\u524d\uff0c\u5efa\u8bae\u5927\u5bb6\u9002\u5f53\u7684\u4fee\u6539waitsem\u51fd\u6570\u548cmy_sleep\u51fd\u6570\uff0c\u5b83\u53ef\u4ee5\u8ba9\u6211\u4eec\u66f4\u597d\u7684\u611f\u77e5\u5f53\u524d\u8fdb\u7a0b\u7684\u201c\u6b7b\u6d3b\u201d\u3002<\/p>\n
int waitsem(int semid,int index)\r\n{\r\n\twhile(semctl(semid,index,GETVAL,0)==0)\r\n\t{\r\n\t\tsleep(1);\r\n\t\tprintf(\"I am waiting ..\\n\");\r\n\t}\r\n\treturn 1;\r\n}\r\nvoid my_sleep(int i)\r\n{\r\n\twhile(i--)\r\n\t{\r\n\t\tprintf(\"writer is sleeping..\\n\");\/\/\u5199\u8fdb\u7a0b\u4e2d\u7684my_sleep\u505a\u76f8\u5e94\u6539\u52a8\r\n\t\tsleep(1);\r\n\t}\r\n}<\/pre>\n
\u8fd9\u6837\u589e\u52a0\u4e86\u4e00\u4e9b\u63d0\u793a\u8bed\uff0c\u518d\u5206\u522b\u5728\u4e24\u4e2a\u7ec8\u7aef\u8fd0\u884c\u8bfb\u5199\u8fdb\u7a0b\uff0c\u53ef\u4ee5\u53d1\u73b0\u7b2c\u4e00\u4e2amy_sleep\u51fd\u6570\u7684\u4f5c\u7528\u5c31\u662f\u6545\u610f\u5ef6\u957f\u8bfb\uff08\u5199\uff09\u8fdb\u7a0b\u5728\u4e34\u754c\u533a\u7684\u8bbf\u95ee\u65f6\u95f4\uff0c\u4ee5\u4f7f\u5f97\u5199\uff08\u8bfb\uff09\u8fdb\u7a0b\u963b\u585e\u3002\u800c\u7b2c\u4e8c\u4e2amy_sleep\u51fd\u6570\u5219\u662f\u6545\u610f\u963b\u585e\u5199\uff08\u8bfb\uff09\u8fdb\u7a0b\uff0c\u8ba9\u8bfb\uff08\u5199\uff09\u8fdb\u7a0b\u6709\u65f6\u95f4\u53bb\u8bfb\u5171\u4eab\u5185\u5b58\u3002\u597d\u4e86\uff0c\u65e2\u7136\u73b0\u5728\u638c\u63e1\u4e86\u4fe1\u53f7\u91cf\u548c\u5171\u4eab\u5185\u5b58\uff0c\u90a3\u4e48\u6211\u4eec\u5c31\u53ef\u4ee5\u8bd5\u7740\u53bb\u5b8c\u6210\u4e00\u4e9b\u7b80\u5355\u7684\u540c\u6b65\u4e92\u65a5\u7684\u9898\u76ee\u4e86\uff0c\u7ee7\u7eed\u52a0\u6cb9\u5427 \"e49\"  \"e49\"  \"e49\" \uff01<\/p>\n","protected":false},"excerpt":{"rendered":"
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