On Thu, Dec 07, 2006 at 11:58:23PM +0000, David Howells wrote:
> Russell King <[email protected]> wrote:
>
> > Incorrect. pre-v6 ARM bitops for test_and_xxx_bit() all do:
> >
> > save and disable irqs
> > load value
> > test bit
> > if not in desired state, alter bit and write it back
> > restore irqs
>
> Hmmm... ARM has two implementations. One in the header files which is what I
> consulted when writing that email:
>
> static inline void ____atomic_set_bit(unsigned int bit, volatile unsigned long *p)
> {
> unsigned long flags;
> unsigned long mask = 1UL << (bit & 31);
>
> p += bit >> 5;
>
> raw_local_irq_save(flags);
> *p |= mask;
> raw_local_irq_restore(flags);
> }
>
> And the other in the libs which does as you say. Why the one in the header
> file at all?
These are the constant versions, where the compiler can optimise the
mask and word offset itself.
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of:
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