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    SubjectRe: [PATCH] i386 spinlocks should use the full 32 bits, not only 8 bits

    * Linus Torvalds <torvalds@osdl.org> wrote:

    >
    >
    > On Fri, 21 Oct 2005, Ingo Molnar wrote:
    > >
    > > the unlock is simple even in the preemption case
    >
    > No it's not. It needs to decrement the preemption counter and test it.

    arghhh. Right you are. I even had the proper solution coded up initially
    (i had || defined(CONFIG_PREEMPT)) but dropped it due to fatal brain
    error. Been hacking on way too much ktimer code today ... Hopefully
    better patch attached. Booted on SMP+PREEMPT x86. But i'd really advise
    you against taking patches from me tonight :-|

    Ingo

    Signed-off-by: Ingo Molnar <mingo@elte.hu>

    include/linux/spinlock.h | 15 ++++++++++++---
    1 files changed, 12 insertions(+), 3 deletions(-)

    Index: linux/include/linux/spinlock.h
    ===================================================================
    --- linux.orig/include/linux/spinlock.h
    +++ linux/include/linux/spinlock.h
    @@ -171,9 +171,18 @@ extern int __lockfunc generic__raw_read_
    #define write_lock_irq(lock) _write_lock_irq(lock)
    #define write_lock_bh(lock) _write_lock_bh(lock)

    -#define spin_unlock(lock) _spin_unlock(lock)
    -#define write_unlock(lock) _write_unlock(lock)
    -#define read_unlock(lock) _read_unlock(lock)
    +/*
    + * We inline the unlock functions in the nondebug case:
    + */
    +#if defined(CONFIG_DEBUG_SPINLOCK) || defined(CONFIG_PREEMPT)
    +# define spin_unlock(lock) _spin_unlock(lock)
    +# define read_unlock(lock) _read_unlock(lock)
    +# define write_unlock(lock) _write_unlock(lock)
    +#else
    +# define spin_unlock(lock) __raw_spin_unlock(&(lock)->raw_lock)
    +# define read_unlock(lock) __raw_read_unlock(&(lock)->raw_lock)
    +# define write_unlock(lock) __raw_write_unlock(&(lock)->raw_lock)
    +#endif

    #define spin_unlock_irqrestore(lock, flags) \
    _spin_unlock_irqrestore(lock, flags)
    -
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