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Date: Fri, 24 Feb 2012 11:14:57 -0500 From: KOSAKI Motohiro <kosaki.motohiro@...il.com> To: Siddhesh Poyarekar <siddhesh.poyarekar@...il.com> CC: KOSAKI Motohiro <kosaki.motohiro@...il.com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, Alexander Viro <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org, Jamie Lokier <jamie@...reable.org>, vapier@...too.org, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [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? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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