Messages in this thread | | | Date | Fri, 24 Feb 2012 11:14:57 -0500 | From | KOSAKI Motohiro <> | Subject | Re: [PATCH] Mark thread stack correctly in proc/<pid>/maps |
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>> Sigh. No, I missed one thing. If application use >> makecontext()/swapcontext() pair, >> ESP is not reliable way to detect pthread stack. At that time the >> stack is still marked >> as anonymous memory. > > This is not wrong, because it essentially gives the correct picture of > the state of that task -- the task is using another vma as a stack > during that point and not the one it was allotted by pthreads during > thread creation. > > I don't think we can successfully stick to the idea of trying to mark > stack space allocated by pthreads but not used by any task *currently* > as stack as long as the allocation happens outside the kernel space. > The only way to mark this is either by marking the stack as > VM_GROWSDOWN (which will make the stack grow and break some pthreads > functions) or create a new flag, which a simple display such as this > does not deserve. So it's best that this sticks to what the kernel > *knows* is being used as stack.
Oh, maybe generically you are right. but you missed one thing. Before your patch, stack or not stack are address space property. thus, using /proc/pid/maps makes sense. but after your patch, it's no longer memory property. applications can use heap or mapped file as a stack. then, at least, current your code is wrong. the code assume each memory property are exclusive.
Moreover, if pthread stack is unimportant, I wonder why we need this patch at all. Which application does need it? and When?
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