trace如下：

[ 1828.731377] sd_open-629
[ 1828.731385] Pid: 3591, comm: hald-addon-stor Not tainted 2.6.27.42 #11
[ 1828.731390]  [] ? printk+0x18/0x1d
[ 1828.731406]  [] sd_open+0x39/0x210
[ 1828.731413]  [] do_open+0x1f9/0x2c0
[ 1828.731419]  [] ? path_walk+0xa2/0xb0
[ 1828.731425]  [] blkdev_open+0x33/0x70
[ 1828.731430]  [] __dentry_open+0xb7/0x260
[ 1828.731436]  [] nameidata_to_filp+0x47/0x60
[ 1828.731442]  [] ? blkdev_open+0x0/0x70
[ 1828.731448]  [] do_filp_open+0x1b5/0x780
[ 1828.731453]  [] ? scsi_device_put+0x30/0x50
[ 1828.731459]  [] ? sd_release+0x6a/0x110
[ 1828.731464]  [] ? iput+0x20/0x60
[ 1828.731469]  [] ? mntput_no_expire+0x1d/0x120
[ 1828.731474]  [] ? alloc_fd+0xe0/0x100
[ 1828.731479]  [] do_sys_open+0x5d/0xf0
[ 1828.731483]  [] ? copy_to_user+0x36/0x120
[ 1828.731489]  [] sys_open+0x29/0x40
[ 1828.731494]  [] sysenter_do_call+0x12/0x2f
[ 1828.731499]  =======================
[ 1828.731502] scsi_disk_get-347
[ 1828.731504] __scsi_disk_get-332
[ 1828.731509] sd_media_changed-824
[ 1828.731710] sd_prep_fn-606
[ 1828.748590] usb_stor_control_thread() line-322  loop times 968
[ 1828.748593] 
[ 1828.748646] sd_media_changed-885
[ 1828.748661] sd_release-706
[ 1828.748664] scsi_disk_put-370


插上usb的时候，dmesg看到的都是这样的轮询，sysenter_do_call这个函数是怎么触发的？

http://blog.csdn.net/aaronychen/archive/2008/01/31/2074148.aspx

此人的博客，希望对你有帮助。