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    SubjectRe: [PATCH] spinlock: __raw_spin_is_locked() should return true for UP
    On Tue, Aug 18, 2009 at 07:40:16PM -0700, Linus Torvalds wrote:
    >
    >
    > On Tue, 18 Aug 2009, Kumar Gala wrote:
    > >
    > > I agree its a little too easy to abuse spin_is_locked. However we should be
    > > consistent between spin_is_locked on UP between with and without
    > > CONFIG_DEBUG_SPINLOCK enabled.
    >
    > No we shouldn't.
    >
    > With CONFIG_DEBUG_SPINLOCK, you have an actual lock variable for debugging
    > purposes, so spin_is_locked() can clearly return a _valid_ answer, and
    > should do so.
    >
    > Without DEBUG_SPINLOCK, there isn't any answer to return.
    >
    > So there's no way we can or should be consistent. In one case an answer
    > exists, in another one the answer is meaningless and doesn't exist.

    I always thought behaviour should be consistent between code with
    debugging on and code without. Otherwise you may end up with cases of
    "it starts working when I turn on debugging" which are a pain to fix.
    Has something changed?

    Or in other words, do you think lockdep should try solving deadlocks
    instead of just reporting them for instance?

    OG.


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