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RE: Review patches of user space kprobe
- From: "Zhang, Yanmin" <yanmin dot zhang at intel dot com>
- To: "Roland McGrath" <roland at redhat dot com>, <prasanna at in dot ibm dot com>
- Cc: <systemtap at sources dot redhat dot com>, "Keshavamurthy, Anil S" <anil dot s dot keshavamurthy at intel dot com>, "Mao, Bibo" <bibo dot mao at intel dot com>
- Date: Mon, 9 Jan 2006 10:03:47 +0800
- Subject: RE: Review patches of user space kprobe
>>-----Original Message-----
>>From: systemtap-owner@sourceware.org [mailto:systemtap-owner@sourceware.org] On Behalf Of Roland McGrath
>>Sent: 2006年1月6日 18:31
>>To: prasanna@in.ibm.com
>>Cc: Zhang, Yanmin; systemtap@sources.redhat.com; Keshavamurthy, Anil S; Mao, Bibo
>>Subject: Re: Review patches of user space kprobe
>>
>>> I think the dll's share the same vma's.
>>
>>You cannot rely on mapping addresses being the same, they are not always
>>so. There are always separate vm_area_struct's in separate processes even
>>when they appear to be identical.
I agree with Roland. Although sometimes they appear to be identical, the vma themselves are different. And a vma might be released/reallocated before readpage/readpages are called. It's easy to introduce race condition when storing temp member in uprobe.