>in short, that per-process stack has to exist the whole time >the
>process does, since it's actually keeping track of some >process
>information. you couldn't do that if you just used the >user-space stack.
Why could not we do that in case of one stack?
Ok. Thread_info structure is stored in this way so that you can access it directly through stack pointer. Which gives a performance improvement. And again thread_info is stored in this way because there is a kernel mode stack concept for each process. If there is no kernel mode stack you can store thread_info like you store task_struct. task_struct is also required for the entire life time of the process.
I feel there are two stacks for security reasons but I dont know what they are precisely.
- A Sahlot
On Thu, Apr 24, 2008 at 7:05 PM, Robert P. J. Day <rpjday@xxxxxxxxxxxxxx> wrote:
On Thu, 24 Apr 2008, sahlot arvind wrote:while there may be other reasons, there's one obvious one -- as i
> Yes. I agree with Robert. There are two stacks per process. But why
> cannot we just use one stack as I said earlier?
mentioned in my earlier email, the kernel likes to store a small,
pre-process "thread_info" structure at the bottom of the kernel stack.
in short, that per-process stack has to exist the whole time the
process does, since it's actually keeping track of some process
information. you couldn't do that if you just used the user-space
stack.
rday
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Robert P. J. Day
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Have classroom, will lecture.
http://crashcourse.ca Waterloo, Ontario, CANADA
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