systemtap question..

[Frank Ch. Eigler]

"Peter Teoh" <htmldeveloper@gmail.com> writes:

> as discovered by narasimhan, the following script will lead to kernel
> freezing and hanged for me:
> I execute via "stap -kvvv script.stp" command.

Please see the "HowToReportBugs" systemtap wiki page.


> Question is:  why does he get a compilation error when using the -u
> option?  (same for me as well, which goes away when removed?)

>> probe kernel.function ("vfs_read"), kernel.function("vfs_write")
>> {
>>       inode = $file->f_dentry->d_inode->i_ino
>>       dev_nr = $file->f_dentry->d_inode->i_sb->s_dev
>>
>> }

The reason is that this probe does nothing.  The "inode" and "dev_nr"
variables being fetched are not printed, so systemtap figures they
were not needed in the first place, and elides the $-expressions.  The
"-u" (unoptimized) flag preserves such code.

- FChE