Messages in this thread | | | Date | Fri, 8 Dec 2006 11:14:11 +0000 | From | Russell King <> | Subject | Re: [PATCH 3/3] WorkStruct: Use direct assignment rather than cmpxchg() |
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On Thu, Dec 07, 2006 at 11:58:23PM +0000, David Howells wrote: > Russell King <rmk+lkml@arm.linux.org.uk> 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: - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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