Re: [PATCH 3/6] C-language equivalents of include/asm-*/bitops.h

Hirokazu Takata
2006-01-27T12:51:47Z

Hello Mita-san, and folks,

From: mita@miraclelinux.com (Akinobu Mita)
Subject: [PATCH 3/6] C-language equivalents of include/asm-*/bitops.h
Date: Wed, 25 Jan 2006 20:32:06 +0900
> o generic {,test_and_}{set,clear,change}_bit() (atomic bitops)
>
> This patch introduces the C-language equivalents of the functions below:
> void set_bit(int nr, volatile unsigned long *addr);
> void clear_bit(int nr, volatile unsigned long *addr);
...
> int test_and_change_bit(int nr, volatile unsigned long *addr);
>
> HAVE_ARCH_ATOMIC_BITOPS is defined when the architecture has its own
> version of these functions.
>
> This code largely copied from:
> include/asm-powerpc/bitops.h
> include/asm-parisc/bitops.h
> include/asm-parisc/atomic.h

Could you tell me more about the new generic {set,clear,test}_bit()
routines?

Why do you copied these routines from parisc and employed them
as generic ones?
I'm not sure whether these generic {set,clear,test}_bit() routines
are really generic or not.

> +/* Can't use raw_spin_lock_irq because of #include problems, so
> + * this is the substitute */
> +#define _atomic_spin_lock_irqsave(l,f) do { \
> + raw_spinlock_t *s = ATOMIC_HASH(l); \
> + local_irq_save(f); \
> + __raw_spin_lock(s); \
> +} while(0)
> +
> +#define _atomic_spin_unlock_irqrestore(l,f) do { \
> + raw_spinlock_t *s = ATOMIC_HASH(l); \
> + __raw_spin_unlock(s); \
> + local_irq_restore(f); \
> +} while(0)

Is there a possibility that these routines affect for archs
with no HAVE_ARCH_ATOMIC_BITOPS for SMP ?
I think __raw_spin_lock() is sufficient and local_irqsave() is
not necessary in general atomic routines.

If the parisc's LDCW instruction required disabling interrupts,
it would be parisc specific and not generic case, I think,
although I'm not familier with the parisc architecture...

-- Takata