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    SubjectRe: [PATCH 01/12] Use mutex instead of semaphore in driver core
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    On Sat, 2007-12-29 at 22:42 -0800, David Brownell wrote:
    > On Saturday 29 December 2007, Alan Stern wrote:

    > > There's no way to remove these, which means there's
    > > no way to prevent lockdep from issuing a warning.
    >
    > There may be no *efficient* way to do that. If it tracked
    > every lock individually these false alarms could go away;
    > but that would increase the overhead to create and destroy
    > such locks too.

    No, tracking locks individually defeats the power of lockdep, that is
    warning of lock inversion before it actually happens. That really
    requires classes.

    Annotating a tree requires grouping per level, and that isn't
    particularly hard (although I haven't yet tried it for the device tree -
    doing this conversion is still on my todo list). The hardest part of the
    device->sem conversion is the suspend/resume part, where it locks the
    whole tree and lockdep is limited in tracking held locks.





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