2010/10/11 Arnd Bergmann <arnd@xxxxxxxx>: > On Sunday 10 October 2010 17:07:26 Akinobu Mita wrote: >> Some architectures use spinlock to implement it >> (asm-generic/bitops/ext2-atomic.h). Most other architectures use >> test_and_set_bit() and test_and_clear_bit() as this patch shows. >> >> Why are there two implementations? test_and_{set,clear}_bit() are more >> costly operations than spinlock for some architectures? > > I would guess that is only true on architectures that implement all atomics > using a hashed spinlock like cris, sparc32 or parisc. This way the user > can decide which spinlock to use rather than have the arch code calculate > a hash on the pointer. Thanks. It looks quite right. > This is an ext2 specific micro-optimization that I don't think makes > sense in the generic le bitops code. OK, I'll only rename ext2 non-atomic bitops to le bitops and keep ext2 atomic bitops for now. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html