lkml.org 
[lkml]   [2012]   [Feb]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] Mark thread stack correctly in proc/<pid>/maps
>> 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?



\
 
 \ /
  Last update: 2012-02-24 17:17    [W:7.921 / U:0.004 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site