hi,
Halil Demirezen wrote:
> in linux/spinlock.h the spinlocks are defined
> and i want to know what kind of a reasonability does it have to define
> spin_lock and spin_unlock in the following way.
>
>
> #define spin_lock(lock) do {} while(0)
> #define spin_unlock(lock) (void)...
>
that's the definition for UP, not preemptible kernel (they don't need
spinlock).
the real spinlock for SMP are defined (#ifdef CONFIG_SMP) in the
architecture dependant headers (<asm/spinlock.h>).
if the kernel is preemptable (2.5 or patched) even uniprocessor machines
have to care about race conditions so there's another #ifdef who add
preempt lock stuff at the spinlock.
Gianluca
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