Messages in this thread | | | Subject | Re: get_task_struct() | From | Robert Love <> | Date | Sat, 17 Apr 2004 12:19:50 -0400 |
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On Sat, 2004-04-17 at 12:46 -0300, Fabiano Ramos wrote:
> Inside sys_ptrace, the function get_task_struct is invoked after > retrieving the child's task srtuct pointer. Why is it done? I have > tracked down the code and noticed that it is in fact an increment > on the (page?) counter. Can you help me understand it?
Think of get_task_struct(foo) as a reference count on foo's task structure. So long as the reference count is elevated, foo's task structure cannot be deallocated.
get_task_struct() is called here because sys_ptrace() needs to ensure that the child's task structure does not go away out from under this function, but we do not want to hold the tasklist_lock.
> Is it necessary to call free_task_struct whenever its get counterpart > is called?
Yes, although it is called "put_task_struct()". It is called at the end of this function.
Robert Love
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