nginx源码分析--使用GDB调试nginx

叁歲伎倆 2022-08-27 09:52 322阅读 0赞

gdb是linux上调试应用程序的首选。在进行nginx的调试过程中，首先需要修改Makefile文件。

vi objs/Makefile \#增加 -O0 和 -g 选项; -O0代表不进行优化，-g代表调试模式 CFLAGS =  -pipe -W -Wall -Wpointer-arith -Wno-unused-parameter -g -O0

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       vi 
      <span> </span>objs/Makefile 
     </div> 
     <div>
       #增加 
      <span> </span>-O0 
      <span> </span>和 
      <span> </span>-g 
      <span> </span>选项; 
      <span> </span>-O0代表不进行优化，-g代表调试模式 
     </div> 
     <div>
       CFLAGS 
      <span> </span>= 
      <span> </span>&nbsp;-pipe 
      <span> </span>-W 
      <span> </span>-Wall 
      <span> </span>-Wpointer-arith 
      <span> </span>-Wno-unused-parameter 
      <span> </span>-g 
      <span> </span>-O0 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

当然，也可以添加 -gstabs 代替 -O0 ，二者是等同的。上面这种方法是在 ./configure 之后的。如果想省事的话，可以执行如下操作，避免了后续对 Makefile 文件的修改。

CFLAGS="-g -O0" ./configure

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       CFLAGS= 
      <span>"-g -O0"</span> 
      <span> </span>./configure 
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    </div> </td> 
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</table>

调试nginx总体来说有三种方法。

**一、设置nginx为前台单进程模式**

修改配置文件，增加如下两句：

daemon off; \#关闭守护进程，使之在前台运行 master\_process off; \#关闭主进程，使只有一个进程

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   <td> 
    <div style="font-size:12px!important; line-height:15px!important"> 
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       daemon 
      <span> </span>off; 
      <span>&nbsp;&nbsp;</span>#关闭守护进程，使之在前台运行 
     </div> 
     <div>
       master_process 
      <span> </span>off; 
      <span>&nbsp;&nbsp;</span>#关闭主进程，使只有一个进程 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

这就可以了，启动调试。

gdb nginx run

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       gdb 
      <span> </span>nginx 
      <span> </span> 
     </div> 
     <div>
       run 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

说明：在这个过程中，因为nginx是前台运行，占用了键盘，因此gdb的命令无法输入。需要输入Ctrl+C，暂停nginx，然后设置断点等一系列操作，之后键入 c 则 nginx就会继续运行了。如下所示：

<http://www.gnu.org/software/gdb/bugs/>... Reading symbols from /usr/local/nginx/sbin/nginx...done. (gdb) run Starting program: /usr/local/nginx/sbin/nginx \[Thread debugging using libthread\_db enabled\] ^C Program received signal SIGINT, Interrupt. 0x00007ffff6f14513 in epoll\_wait () from /lib/libc.so.6 (gdb) b ngx\_http\_finalize\_request Breakpoint 1 at 0x430be7: file src/http/ngx\_http\_request.c, line 1939. (gdb) c Continuing.

**二、设置nginx为后台单进程模式**

修改配置文件为：

daemon on; master\_process off;

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       daemon 
      <span> </span>on; 
     </div> 
     <div>
       master_process 
      <span> </span>off; 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

这样就打开了nginx后台运行的模式，启动gdb调试发现如下：

Reading symbols from /usr/local/nginx/sbin/nginx...done. (gdb) run Starting program: /usr/local/nginx/sbin/nginx \[Thread debugging using libthread\_db enabled\] Program exited normally. (gdb)

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       Reading 
      <span> </span>symbols 
      <span> </span>from 
      <span> </span>/usr/local/nginx/sbin/nginx...done. 
     </div> 
     <div>
       (gdb) 
      <span> </span>run 
     </div> 
     <div>
       Starting 
      <span> </span>program: 
      <span> </span>/usr/local/nginx/sbin/nginx 
      <span> </span> 
     </div> 
     <div>
       [Thread 
      <span> </span>debugging 
      <span> </span>using 
      <span> </span>libthread_db 
      <span> </span>enabled] 
     </div> 
     <div>
       &nbsp; 
     </div> 
     <div>
       Program 
      <span> </span>exited 
      <span> </span>normally. 
     </div> 
     <div>
       (gdb) 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

难道进程真的退出了吗？没有，退出的只是nginx的父进程，而fork出来的进程gdb没有跟到，所以出现了这个情况。这种情况下，gdb是有自己的策略的。命令如下：(其实这一点我还是比较困惑的！)

(gdb) shell pidof nginx 5692 (gdb) set follow-fork-mode child \#设置调试子进程，父进程不受影响(相对应的是parent) (gdb) b ngx\_http\_upstream\_cleanup Breakpoint 1 at 0x43db0b: file src/http/ngx\_http\_upstream.c, line 2951.

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       (gdb) 
      <span> </span>shell 
      <span> </span>pidof 
      <span> </span>nginx 
     </div> 
     <div>
       5692 
     </div> 
     <div>
       (gdb) 
      <span> </span>set 
      <span> </span>follow-fork-mode 
      <span> </span> child 
      <span>&nbsp;&nbsp;</span>#设置调试子进程，父进程不受影响(相对应的是parent) 
     </div> 
     <div>
       (gdb) 
      <span> </span>b 
      <span> </span>ngx_http_upstream_cleanup 
     </div> 
     <div>
       Breakpoint 
      <span> </span>1 
      <span> </span>at 
      <span> </span>0x43db0b: 
      <span> </span>file 
      <span> </span>src/http/ngx_http_upstream.c, 
      <span> </span>line 
      <span> </span>2951. 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

**三、设置nginx为后台多进程模式**

这也是nginx的默认运行模式。在这种情况下，使用gdb的attach和detach指令。

首先查看nginx的work\_process进程号是多少，然后直接attach调试就可以了。

Shell

Reading symbols from /usr/local/nginx/sbin/nginx...done. (gdb) run Starting program: /usr/local/nginx/sbin/nginx \[Thread debugging using libthread\_db enabled\] Program exited normally. (gdb) shell pidof nginx 5776 5775 (gdb) attach 5775 Attaching to program: /usr/local/nginx/sbin/nginx, process 5775 Reading symbols from /lib/libpthread.so.0...(no debugging symbols found)...done. \[Thread debugging using libthread\_db enabled\] Loaded symbols for /lib/libpthread.so.0 \#停止调试，使用detach即可 (gdb) detach

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       Reading 
      <span> </span>symbols 
      <span> </span>from 
      <span> </span>/usr/local/nginx/sbin/nginx...done. 
     </div> 
     <div>
       (gdb) 
      <span> </span>run 
     </div> 
     <div>
       Starting 
      <span> </span>program: 
      <span> </span>/usr/local/nginx/sbin/nginx 
      <span> </span> 
     </div> 
     <div>
       [Thread 
      <span> </span>debugging 
      <span> </span>using 
      <span> </span>libthread_db 
      <span> </span>enabled] 
     </div> 
     <div>
       &nbsp; 
     </div> 
     <div>
       Program 
      <span> </span>exited 
      <span> </span>normally. 
     </div> 
     <div>
       (gdb) 
      <span> </span>shell 
      <span> </span>pidof 
      <span> </span>nginx 
     </div> 
     <div>
       5776 
      <span> </span>5775 
     </div> 
     <div>
       (gdb) 
      <span> </span>attach 
      <span> </span>5775 
     </div> 
     <div>
       Attaching 
      <span> </span>to 
      <span> </span>program: 
      <span> </span>/usr/local/nginx/sbin/nginx, 
      <span> </span>process 
      <span> </span>5775 
     </div> 
     <div>
       Reading 
      <span> </span>symbols 
      <span> </span>from 
      <span> </span>/lib/libpthread.so.0...(no 
      <span> </span>debugging 
      <span> </span>symbols 
      <span> </span> found)...done. 
     </div> 
     <div>
       [Thread 
      <span> </span>debugging 
      <span> </span>using 
      <span> </span>libthread_db 
      <span> </span>enabled] 
     </div> 
     <div>
       Loaded 
      <span> </span>symbols 
      <span> </span>for 
      <span> </span>/lib/libpthread.so.0 
     </div> 
     <div>
       &nbsp; 
     </div> 
     <div>
       #停止调试，使用detach即可 
      <br> 
      <br> 
      <br> 
      <br> 
      <br> 
      <br> 
      <br> 
      <br> 
      <br> 
      <p>gdb是linux上调试应用程序的首选。在进行nginx的调试过程中，首先需要修改Makefile文件。</p> 
      <div style="margin-top:12px; margin-bottom:12px; float:none; clear:both; font-size:12px!important; line-height:15px!important; height:auto"> 
       <div> vi objs/Makefile #增加 -O0 和 -g 选项; -O0代表不进行优化，-g代表调试模式 CFLAGS = &nbsp;-pipe -W -Wall -Wpointer-arith -Wno-unused-parameter -g -O0 
       </div> 
       <div style="position:relative; z-index:1; overflow:hidden"> 
        <table style=""> 
         <tbody> 
          <tr> 
           <td> 
            <div style="font-size:12px!important; line-height:15px!important"> 
             <div>
               1 
             </div> 
             <div>
               2 
             </div> 
             <div>
               3 
             </div> 
            </div> </td> 
           <td> 
            <div style="font-size:12px!important; line-height:15px!important"> 
             <div>
               vi 
              <span> </span>objs/Makefile 
             </div> 
             <div>
               #增加 
              <span> </span>-O0 
              <span> </span>和 
              <span> </span>-g 
              <span> </span>选项; 
              <span> </span>-O0代表不进行优化，-g代表调试模式 
             </div> 
             <div>
               CFLAGS 
              <span> </span>= 
              <span> </span>&nbsp;-pipe 
              <span> </span>-W 
              <span> </span>-Wall 
              <span> </span>-Wpointer-arith 
              <span> </span>-Wno-unused-parameter 
              <span> </span>-g 
              <span> </span>-O0 
             </div> 
            </div> </td> 
          </tr> 
         </tbody> 
        </table> 
       </div> 
      </div> 
      <p>当然，也可以添加 -gstabs 代替 -O0 ，二者是等同的。上面这种方法是在 ./configure 之后的。如果想省事的话，可以执行如下操作，避免了后续对 Makefile 文件的修改。</p> 
      <div style="margin-top:12px; margin-bottom:12px; float:none; clear:both; font-size:12px!important; line-height:15px!important; height:auto"> 
       <div> CFLAGS="-g -O0" ./configure 
       </div> 
       <div style="position:relative; z-index:1; overflow:hidden"> 
        <table style=""> 
         <tbody> 
          <tr> 
           <td> 
            <div style="font-size:12px!important; line-height:15px!important"> 
             <div>
               1 
             </div> 
            </div> </td> 
           <td> 
            <div style="font-size:12px!important; line-height:15px!important"> 
             <div>
               CFLAGS= 
              <span>"-g -O0"</span> 
              <span> </span>./configure 
             </div> 
            </div> </td> 
          </tr> 
         </tbody> 
        </table> 
       </div> 
      </div> 
      <p>调试nginx总体来说有三种方法。</p> 
      <p><strong>一、设置nginx为前台单进程模式</strong></p> 
      <p>修改配置文件，增加如下两句：</p> 
      <div style="margin-top:12px; margin-bottom:12px; float:none; clear:both; font-size:12px!important; line-height:15px!important; height:auto"> 
       <div> daemon off; #关闭守护进程，使之在前台运行 master_process off; #关闭主进程，使只有一个进程 
       </div> 
       <div style="position:relative; z-index:1; overflow:hidden"> 
        <table style=""> 
         <tbody> 
          <tr> 
           <td> 
            <div style="font-size:12px!important; line-height:15px!important"> 
             <div>
               1 
             </div> 
             <div>
               2 
             </div> 
            </div> </td> 
           <td> 
            <div style="font-size:12px!important; line-height:15px!important"> 
             <div>
               daemon 
              <span> </span>off; 
              <span>&nbsp;&nbsp;</span>#关闭守护进程，使之在前台运行 
             </div> 
             <div>
               master_process 
              <span> </span>off; 
              <span>&nbsp;&nbsp;</span>#关闭主进程，使只有一个进程 
             </div> 
            </div> </td> 
          </tr> 
         </tbody> 
        </table> 
       </div> 
      </div> 
      <p>这就可以了，启动调试。</p> 
      <div style="margin-top:12px; margin-bottom:12px; float:none; clear:both; font-size:12px!important; line-height:15px!important; height:auto"> 
       <div> gdb nginx run 
       </div> 
       <div style="position:relative; z-index:1; overflow:hidden"> 
        <table style=""> 
         <tbody> 
          <tr> 
           <td> 
            <div style="font-size:12px!important; line-height:15px!important"> 
             <div>
               1 
             </div> 
             <div>
               2 
             </div> 
            </div> </td> 
           <td> 
            <div style="font-size:12px!important; line-height:15px!important"> 
             <div>
               gdb 
              <span> </span>nginx 
              <span> </span> 
             </div> 
             <div>
               run 
             </div> 
            </div> </td> 
          </tr> 
         </tbody> 
        </table> 
       </div> 
      </div> 
      <p>说明：在这个过程中，因为nginx是前台运行，占用了键盘，因此gdb的命令无法输入。需要输入Ctrl+C，暂停nginx，然后设置断点等一系列操作，之后键入 c 则 nginx就会继续运行了。如下所示：</p> 
      <div style="margin-top:12px; margin-bottom:12px; float:none; clear:both; font-size:12px!important; line-height:15px!important; height:auto"> 
       <div> &lt;http://www.gnu.org/software/gdb/bugs/&gt;... Reading symbols from /usr/local/nginx/sbin/nginx...done. (gdb) run Starting program: /usr/local/nginx/sbin/nginx [Thread debugging using libthread_db enabled] ^C Program received signal SIGINT, Interrupt. 0x00007ffff6f14513 in epoll_wait () from /lib/libc.so.6 (gdb) b ngx_http_finalize_request Breakpoint 1 at 0x430be7: file src/http/ngx_http_request.c, line 1939. (gdb) c Continuing. 
       </div> 
       <div style="position:relative; z-index:0; overflow:hidden"> 
        <table style=""> 
         <tbody> 
          <tr> 
           <td> 
            <div style="font-size:12px!important; line-height:15px!important"> 
             <div>
               1 
             </div> 
             <div>
               2 
             </div> 
             <div>
               3 
             </div> 
             <div>
               4 
             </div> 
             <div>
               5 
             </div> 
             <div>
               6 
             </div> 
             <div>
               7 
             </div> 
             <div>
               8 
             </div> 
             <div>
               9 
             </div> 
             <div>
               10 
             </div> 
             <div>
               11 
             </div> 
             <div>
               12 
             </div> 
             <div>
               13 
             </div> 
            </div> </td> 
           <td> 
            <div style="font-size:12px!important; line-height:15px!important"> 
             <div> 
              <span>&lt;</span>http://www.gnu.org/software/gdb/bugs/ 
              <span>&gt;</span>... 
             </div> 
             <div>
               Reading 
              <span> </span>symbols 
              <span> </span>from 
              <span> </span>/usr/local/nginx/sbin/nginx...done. 
             </div> 
             <div>
               (gdb) 
              <span> </span>run 
             </div> 
             <div>
               Starting 
              <span> </span>program: 
              <span> </span>/usr/local/nginx/sbin/nginx 
              <span> </span> 
             </div> 
             <div>
               [Thread 
              <span> </span>debugging 
              <span> </span>using 
              <span> </span> libthread_db 
              <span> </span>enabled] 
             </div> 
             <div>
               &nbsp; 
             </div> 
             <div>
               ^C 
             </div> 
             <div>
               Program 
              <span> </span>received 
              <span> </span>signal 
              <span> </span>SIGINT, 
              <span> </span>Interrupt. 
             </div> 
             <div>
               0x00007ffff6f14513 
              <span> </span>in 
              <span> </span>epoll_wait 
              <span> </span> () 
              <span> </span>from 
              <span> </span>/lib/libc.so.6 
             </div> 
             <div>
               (gdb) 
              <span> </span>b 
              <span> </span>ngx_http_finalize_request 
             </div> 
             <div>
               Breakpoint 
              <span> </span>1 
              <span> </span>at 
              <span> </span>0x430be7: 
              <span> </span>file 
              <span> </span>src/http/ngx_http_request.c, 
              <span> </span>line 
              <span> </span>1939. 
             </div> 
             <div>
               (gdb) 
              <span> </span>c 
             </div> 
             <div>
               Continuing. 
             </div> 
            </div> </td> 
          </tr> 
         </tbody> 
        </table> 
       </div> 
      </div> 
      <p><strong>二、设置nginx为后台单进程模式</strong></p> 
      <p>修改配置文件为：</p> 
      <div style="margin-top:12px; margin-bottom:12px; float:none; clear:both; font-size:12px!important; line-height:15px!important; height:auto"> 
       <div> daemon on; master_process off; 
       </div> 
       <div style="position:relative; z-index:1; overflow:hidden"> 
        <table style=""> 
         <tbody> 
          <tr> 
           <td> 
            <div style="font-size:12px!important; line-height:15px!important"> 
             <div>
               1 
             </div> 
             <div>
               2 
             </div> 
            </div> </td> 
           <td> 
            <div style="font-size:12px!important; line-height:15px!important"> 
             <div>
               daemon 
              <span> </span>on; 
             </div> 
             <div>
               master_process 
              <span> </span>off; 
             </div> 
            </div> </td> 
          </tr> 
         </tbody> 
        </table> 
       </div> 
      </div> 
      <p>这样就打开了nginx后台运行的模式，启动gdb调试发现如下：</p> 
      <div style="margin-top:12px; margin-bottom:12px; float:none; clear:both; font-size:12px!important; line-height:15px!important; height:auto"> 
       <div> Reading symbols from /usr/local/nginx/sbin/nginx...done. (gdb) run Starting program: /usr/local/nginx/sbin/nginx [Thread debugging using libthread_db enabled] Program exited normally. (gdb) 
       </div> 
       <div style="position:relative; z-index:1; overflow:hidden"> 
        <table style=""> 
         <tbody> 
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           <td> 
            <div style="font-size:12px!important; line-height:15px!important"> 
             <div>
               1 
             </div> 
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               2 
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               3 
             </div> 
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               4 
             </div> 
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               5 
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               6 
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               7 
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            </div> </td> 
           <td> 
            <div style="font-size:12px!important; line-height:15px!important"> 
             <div>
               Reading 
              <span> </span>symbols 
              <span> </span>from 
              <span> </span>/usr/local/nginx/sbin/nginx...done. 
             </div> 
             <div>
               (gdb) 
              <span> </span>run 
             </div> 
             <div>
               Starting 
              <span> </span>program: 
              <span> </span>/usr/local/nginx/sbin/nginx 
              <span> </span> 
             </div> 
             <div>
               [Thread 
              <span> </span>debugging 
              <span> </span>using 
              <span> </span>libthread_db 
              <span> </span>enabled] 
             </div> 
             <div>
               &nbsp; 
             </div> 
             <div>
               Program 
              <span> </span>exited 
              <span> </span>normally. 
             </div> 
             <div>
               (gdb) 
             </div> 
            </div> </td> 
          </tr> 
         </tbody> 
        </table> 
       </div> 
      </div> 
      <p>难道进程真的退出了吗？没有，退出的只是nginx的父进程，而fork出来的进程gdb没有跟到，所以出现了这个情况。这种情况下，gdb是有自己的策略的。命令如下：(<span style="color:#800080">其实这一点我还是比较困惑的！</span>)</p> 
      <div style="margin-top:12px; margin-bottom:12px; float:none; clear:both; font-size:12px!important; line-height:15px!important; height:auto"> 
       <div> (gdb) shell pidof nginx 5692 (gdb) set follow-fork-mode child #设置调试子进程，父进程不受影响(相对应的是parent) (gdb) b ngx_http_upstream_cleanup Breakpoint 1 at 0x43db0b: file src/http/ngx_http_upstream.c, line 2951. 
       </div> 
       <div style="position:relative; z-index:1; overflow:hidden"> 
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               1 
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               5 
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            </div> </td> 
           <td> 
            <div style="font-size:12px!important; line-height:15px!important"> 
             <div>
               (gdb) 
              <span> </span>shell 
              <span> </span>pidof 
              <span> </span>nginx 
             </div> 
             <div>
               5692 
             </div> 
             <div>
               (gdb) 
              <span> </span>set 
              <span> </span>follow-fork-mode 
              <span> </span> child 
              <span>&nbsp;&nbsp;</span>#设置调试子进程，父进程不受影响(相对应的是parent) 
             </div> 
             <div>
               (gdb) 
              <span> </span>b 
              <span> </span>ngx_http_upstream_cleanup 
             </div> 
             <div>
               Breakpoint 
              <span> </span>1 
              <span> </span>at 
              <span> </span>0x43db0b: 
              <span> </span>file 
              <span> </span>src/http/ngx_http_upstream.c, 
              <span> </span>line 
              <span> </span>2951. 
             </div> 
            </div> </td> 
          </tr> 
         </tbody> 
        </table> 
       </div> 
      </div> 
      <p><strong>三、设置nginx为后台多进程模式</strong></p> 
      <p>这也是nginx的默认运行模式。在这种情况下，使用gdb的attach和detach指令。</p> 
      <p>首先查看nginx的work_process进程号是多少，然后直接attach调试就可以了。</p> 
      <div style="font-size:12px!important; height:18px!important; line-height:18px!important; margin-top:0px; display:block; position:absolute; z-index:2"> 
       <span></span> 
       <div style="font-size:12px!important; height:18px!important; line-height:18px!important"> 
        <span>Shell</span> 
       </div> 
      </div> 
      <div> Reading symbols from /usr/local/nginx/sbin/nginx...done. (gdb) run Starting program: /usr/local/nginx/sbin/nginx [Thread debugging using libthread_db enabled] Program exited normally. (gdb) shell pidof nginx 5776 5775 (gdb) attach 5775 Attaching to program: /usr/local/nginx/sbin/nginx, process 5775 Reading symbols from /lib/libpthread.so.0...(no debugging symbols found)...done. [Thread debugging using libthread_db enabled] Loaded symbols for /lib/libpthread.so.0 #停止调试，使用detach即可 (gdb) detach 
      </div> 
      <table style=""> 
       <tbody> 
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          <div style="font-size:12px!important; line-height:15px!important"> 
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             1 
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          </div> </td> 
         <td> 
          <div style="font-size:12px!important; line-height:15px!important"> 
           <div>
             Reading 
            <span> </span>symbols 
            <span> </span>from 
            <span> </span>/usr/local/nginx/sbin/nginx...done. 
           </div> 
           <div>
             (gdb) 
            <span> </span>run 
           </div> 
           <div>
             Starting 
            <span> </span>program: 
            <span> </span>/usr/local/nginx/sbin/nginx 
            <span> </span> 
           </div> 
           <div>
             [Thread 
            <span> </span>debugging 
            <span> </span>using 
            <span> </span>libthread_db 
            <span> </span>enabled] 
           </div> 
           <div>
             &nbsp; 
           </div> 
           <div>
             Program 
            <span> </span>exited 
            <span> </span>normally. 
           </div> 
           <div>
             (gdb) 
            <span> </span>shell 
            <span> </span>pidof 
            <span> </span>nginx 
           </div> 
           <div>
             5776 
            <span> </span>5775 
           </div> 
           <div>
             (gdb) 
            <span> </span>attach 
            <span> </span>5775 
           </div> 
           <div>
             Attaching 
            <span> </span>to 
            <span> </span>program: 
            <span> </span>/usr/local/nginx/sbin/nginx, 
            <span> </span>process 
            <span> </span>5775 
           </div> 
           <div>
             Reading 
            <span> </span>symbols 
            <span> </span>from 
            <span> </span>/lib/libpthread.so.0...(no 
            <span> </span>debugging 
            <span> </span>symbols 
            <span> </span> found)...done. 
           </div> 
           <div>
             [Thread 
            <span> </span>debugging 
            <span> </span>using 
            <span> </span>libthread_db 
            <span> </span>enabled] 
           </div> 
           <div>
             Loaded 
            <span> </span>symbols 
            <span> </span>for 
            <span> </span>/lib/libpthread.so.0 
           </div> 
           <div>
             &nbsp; 
           </div> 
           <div>
             #停止调试，使用detach即可 
           </div> 
          </div> </td> 
        </tr> 
       </tbody> 
      </table> 
      <br> 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>