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    SubjectRe: 2.6.17-rc5-mm2
    On Thu, 01 Jun 2006 19:27:41 +0200
    Arjan van de Ven <arjan@linux.intel.com> wrote:

    >
    > > > http://www.stardust.webpages.pl/files/mm/2.6.17-rc5-mm2/bug_2.jpg
    > >
    > > So it's claiming that we're taking multiple i_mutexes.
    > >
    > > I can't immediately see where we took the outermost i_mutex there.
    >
    > inlining caused one level to be removed from the backtrace
    > one level is in fs_remove_file, the sub level is usbfs_unlink (called
    > from fs_remove_file)

    OK.

    I'll duck this patch for now, pending a tested-n-changelogged one, please.

    > > Nor is
    > > it immediately obvious why this is considered to be deadlockable?
    >
    > what is missing is that we tell lockdep that there is a parent-child
    > relationship between those two i_mutexes, so that it knows that 1)
    > they're separate and 2) that the lock take order is parent->child
    >
    >
    > > (lockdep tells us that a mutex was taken at "mutex_lock+0x8/0xa", which is
    > > fairly useless. We need to report who the caller of mutex_lock() was).
    >
    > yeah this has been bugging me as well; either via a wrapper around
    > mutex_lock or via the gcc option to backwalk the stack (but that only
    > works with frame pointers enabled.. sigh)

    Actually, __builtin_return_address(0) works OK with -fomit-frame-pointer,
    and that's all we need here.

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