pv

来自「linu系统编程基础知识」· 代码 · 共 13 行

  T1                  T2                        free=false;
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while(free);        while(free);       进入区
free=true;          free=true;
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read(x);            read(x);           临界区

if(x>=1)              if(x>=1)
   x=x-1;                x=x-1;

write(x);            write(x);
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free=false;           free=false;      退出区