Linux cpu佔用率居高不下 調試

Linux cpu佔用率居高不下 調試

今天偵錯工具，使用top命令後，發現程式的cpu佔用率很高，一直在99，這很可怕，所以來調試。

使用top命令，得如下結果

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1997 root 20 0 358m 71m 3208 S 99.1 7.2 81:53.50 test
1 root 20 0 24332 2044 1176 S 0.0 0.2 0:01.36 init
2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd
3 root 20 0 0 0 0 S 0.0 0.0 0:46.51 ksoftirqd/0
4 root 20 0 0 0 0 S 0.0 0.0 0:38.53 kworker/0:0
6 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0

可知test的PID為1997

然後具體查看test裡線程的cpu使用方式

使用 top -H -p 1997 命令

root@bkjia:~# top -H -p 1997

top - 17:19:47 up 15 days, 34 min, 4 users, load average: 1.02, 1.06, 1.06
Tasks: 8 total, 1 running, 7 sleeping, 0 stopped, 0 zombie
Cpu(s): 99.3%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.3%si, 0.3%st
Mem: 1017924k total, 887500k used, 130424k free, 85928k buffers
Swap: 0k total, 0k used, 0k free, 351280k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
2005 root 20 0 358m 71m 3208 R 99.3 7.2 83:44.47 test
2001 root 20 0 358m 71m 3208 S 0.3 7.2 0:08.66 test 
2004 root 20 0 358m 71m 3208 S 0.3 7.2 0:19.61 test 
1997 root 20 0 358m 71m 3208 S 0.0 7.2 0:26.24 test 
1999 root 20 0 358m 71m 3208 S 0.0 7.2 0:00.06 test 
2000 root 20 0 358m 71m 3208 S 0.0 7.2 0:00.00 test
2002 root 20 0 358m 71m 3208 S 0.0 7.2 0:05.86 Server Listen(2
2003 root 20 0 358m 71m 3208 S 0.0 7.2 0:00.00 Server Accept(2

可得線程中CPU佔有率最高的線程的PID是2005

使用gdb icdn 2005 命令

root@bkjia:~# gdb icdn 2005
GNU gdb (Ubuntu/Linaro 7.4-2012.04-0ubuntu2.1) 7.4-2012.04
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
For bug reporting instructions, please see:
<http://bugs.launchpad.net/gdb-linaro/>...
icdn: No such file or directory.
Attaching to process 2005

warning: process 2005 is a cloned process
Reading symbols from /home/bkjia/test/snmptrapd...done.
Reading symbols from /usr/lib/libnetsnmp.so.30...done.
Loaded symbols for /usr/lib/libnetsnmp.so.30
Reading symbols from /lib/x86_64-linux-gnu/libpthread.so.0...(no debugging symbols found)...done.
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Loaded symbols for /lib/x86_64-linux-gnu/libpthread.so.0
Reading symbols from /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18
Reading symbols from /usr/local/lib/libstd.so...(no debugging symbols found)...done.
Loaded symbols for /usr/local/lib/libstd.so
Reading symbols from /lib/x86_64-linux-gnu/libc.so.6...(no debugging symbols found)...done.
Loaded symbols for /lib/x86_64-linux-gnu/libc.so.6
Reading symbols from /lib/x86_64-linux-gnu/librt.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib/x86_64-linux-gnu/librt.so.1
Reading symbols from /lib/x86_64-linux-gnu/libcrypto.so.1.0.0...(no debugging symbols found)...done.
Loaded symbols for /lib/x86_64-linux-gnu/libcrypto.so.1.0.0
Reading symbols from /lib64/ld-linux-x86-64.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib64/ld-linux-x86-64.so.2
Reading symbols from /lib/x86_64-linux-gnu/libz.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib/x86_64-linux-gnu/libz.so.1
Reading symbols from /lib/x86_64-linux-gnu/libdl.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib/x86_64-linux-gnu/libdl.so.2
Reading symbols from /lib/x86_64-linux-gnu/libm.so.6...(no debugging symbols found)...done.
Loaded symbols for /lib/x86_64-linux-gnu/libm.so.6
Reading symbols from /usr/local/lib/libudt.so...(no debugging symbols found)...done.
Loaded symbols for /usr/local/lib/libudt.so
Reading symbols from /usr/lib/x86_64-linux-gnu/libstdc++.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/x86_64-linux-gnu/libstdc++.so.6
Reading symbols from /lib/x86_64-linux-gnu/libgcc_s.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib/x86_64-linux-gnu/libgcc_s.so.1
Reading symbols from /lib/x86_64-linux-gnu/libnss_files.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib/x86_64-linux-gnu/libnss_files.so.2
execute_search () at test.c:310

從最後一行可知，線程2005啟動並執行是execute_search這個函數，然後查看該函數，發現有這樣一段

 

while(g_search_state == 1)
{
　　tmp = g_data_list->phead->next;

　　if (tmp)
　　{
　　　　pthread_mutex_lock(&g_mysql_mutex);
　　　　res.result = search_mysql(tmp->sn, &(res.machine));
　　　　pthread_mutex_unlock(&g_mysql_mutex);

　　　　snprintf(res.sn, sizeof(res.sn), "%s", tmp->sn);
　　}
}

由於tmp長期為NULL，所以這變成了一個while的死迴圈，而死迴圈極為佔用記憶體，於是再下面加上usleep(50000)，問題解決。

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