From: Manfred Spraul <manfred@colorfullife.com>
To: Kirill Korotaev <dev@sw.ru>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Again: Fix multithread coredump deadlock (patch Manfred Spraul)
Date: Thu, 03 Jul 2003 19:02:15 +0200 [thread overview]
Message-ID: <3F046197.40600@colorfullife.com> (raw)
In-Reply-To: <200307031238.10570.dev@sw.ru>
Kirill Korotaev wrote:
>Hi!
>
>There was a patch some time ago included in linux-2.4.17-pre6 which fixed mmap
>semaphore deadlock in do_coredump (double down_read() on mmap_sem).
>This fix introduces down_write() on mmap_sem and uses get_user_pages()
>function to avoid do_page_fault().
>The question is why down_write() is used in elf_core_dump() (instead of
>down_read())?
>
>
down_write is required to prevent expand_stack() from growing the stack
- expand_stack is called by the page fault handler under
down_read(&->mmap_sem) and changes vma->vm_start. A change of vm_start
between writing the program headers and the actual segment dump would
corrupt the coredump.
--
Manfred
prev parent reply other threads:[~2003-07-03 16:48 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-07-03 8:38 Again: Fix multithread coredump deadlock (patch Manfred Spraul) Kirill Korotaev
2003-07-03 17:02 ` Manfred Spraul [this message]
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