今天調試程序，使用top命令後，發現程序的cpu占用率很高，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使用情況
使用 top -H -p 1997 命令
root@linuxidc:~# 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占有率最高的線程的PID是2005
使用gdb icdn 2005 命令
root@linuxidc:~# 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/linuxidc/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運行的是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的死循環，而死循環極為占用內存，於是再下面加上usleep(50000)，問題解決。
