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    SubjectRe: [PATCH 1/3][-mm] add class_reclassify macro
    On Tue, 20 May 2008 17:55:54 +0800 Dave Young <hidave.darkstar@gmail.com> wrote:

    > Converting class semaphore to mutex cause lockdep warnings due to
    > class_interface_register/unregister will possible call device_add/del

    Shouldn't we just fix that?

    > For the class_interface users here add a class_reclassify macro to
    > reclassify the lock class of their struct class.
    >
    > Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
    >
    > ---
    > include/linux/device.h | 7 +++++++
    > 1 file changed, 7 insertions(+)
    >
    > --- linux/include/linux/device.h 2008-05-19 12:29:54.000000000 +0800
    > +++ linux.new/include/linux/device.h 2008-05-19 14:42:25.000000000 +0800
    > @@ -529,4 +529,11 @@ extern const char *dev_driver_string(str
    > MODULE_ALIAS("char-major-" __stringify(major) "-" __stringify(minor))
    > #define MODULE_ALIAS_CHARDEV_MAJOR(major) \
    > MODULE_ALIAS("char-major-" __stringify(major) "-*")
    > +
    > +#define class_reclassify(class) \
    > +do { \
    > + static struct lock_class_key class_key; \
    > + lockdep_set_class_and_name(&(class)->mutex, &class_key, \
    > + (class)->name); \
    > +} while (0)
    > #endif /* _DEVICE_H_ */

    I think it would need a lavish comment explaining what it is for, and
    the reasons for its existence.

    Perhaps this should be a kernel-wide thing in lockdep.h. But then that
    would invite people to use it, and it looks like a bad thing.

    device.h does not include lockdep.h, so putting this here assumes that
    callees have already included lockdep.h. This is the sort of
    assumption which leads to compilation errors.



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