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    SubjectRe: [PATCH 7/7] driver-core : convert semaphore to mutex in struct class
    On Jan 18, 2008 4:23 PM, Jarek Poplawski <jarkao2@gmail.com> wrote:
    > On Fri, Jan 18, 2008 at 03:48:02PM +0800, Dave Young wrote:
    > > On Jan 18, 2008 3:38 PM, Jarek Poplawski <jarkao2@gmail.com> wrote:
    > ...
    > > > IMHO, it would be nice to get the real state of current lockdep
    > > > problems here to figure out if there is any chance to do this right &
    > > > without any warnings with current lockdep. If I got it right from
    > > > earlier threads it might be impossible with USB, at least.
    > >
    > > I don't think so, usb doesn't be affected by struct class mutex, they
    > > only use the lock of struct device. As I replied before, the lockdep
    > > issue exist only between class_interface and class_device.
    >
    > OK, but I've meant possibility of changing their own semaphores later.
    >
    > > > So, since I think these nesting levels seem to be wrong in 7/7 patch,
    > > > maybe it's better to exclude it from this patchset, and to try this as
    > > > testing for some time.
    > >
    > > I may file the updated patch with more nesting changes and test it of
    > > course. Actually I should have done it, thanks.
    > ...
    > > 1) Using CLASS_NORMAL/CLASS_PARENT/CLASS_CHILD will be enough.
    > > or
    > > 2) Simply add SINGLE_LEVEL_NESTING in class_device_add and other
    > > class_device functions because it is the only possible nest-lock place
    > > as I know.
    >
    > If SINGLE_LEVEL_NESTING is enough? (means 2 levels total)

    I think so.

    >
    > I think you should more care about real (logical) relations here, than
    > what's enough to get rid of lockdep warnings.

    You are quite right, thanks.

    >
    > Since there are not so much of these changes, you can try both
    > variants.

    Will do.

    >I'll be glad to look at this - maybe I'll mangage to figure
    > out BTW, what it's all about...
    >
    > Jarek P.
    >


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